From 716d2f599a0a7031590c341973fdad1f77851abf Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Mon, 16 Nov 2020 11:25:46 -0700
Subject: [PATCH 01/12] Fixed minor formatting of output

Added a blank to the output afer a comma.

[ticket: X]
---
 src/tests/logger/test_stdlib_logger.f90 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tests/logger/test_stdlib_logger.f90 b/src/tests/logger/test_stdlib_logger.f90
index 53df6269e..9c7c9944e 100644
--- a/src/tests/logger/test_stdlib_logger.f90
+++ b/src/tests/logger/test_stdlib_logger.f90
@@ -47,7 +47,7 @@ program test_stdlib_logger
     print *
     print *, 'running log_text_error'
     call global % log_text_error( 'This text should be written to UNIT1' // &
-                                  'and UNIT3 and not to OUTPUT_UNIT.',      &
+                                  ' and UNIT3 and not to OUTPUT_UNIT.',     &
                                   column = 25,                              &
                                   summary = 'There is no real error here.', &
                                   filename = 'dummy.txt',                   &

From 1fa3a3e80c4f7ba28fa4d2d1fd7ca24911d33188 Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Mon, 16 Nov 2020 11:27:28 -0700
Subject: [PATCH 02/12] Added logger to the index

Added one line to the index referencing stdlib_logger.html.

[ticket: X]
---
 doc/specs/index.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/specs/index.md b/doc/specs/index.md
index 91284c2df..ba43e893a 100644
--- a/doc/specs/index.md
+++ b/doc/specs/index.md
@@ -14,6 +14,7 @@ This is and index/directory of the specifications (specs) for each new module/fe
  - [error](./stdlib_error.html) - Catching and handling errors
  - [IO](./stdlib_io.html) - Input/output helper & convenience
  - [linalg](./stdlib_linalg.html) - Linear Algebra
+ - [logger](./stdlib_logger.html) - Runtime logging system
  - [optval](./stdlib_optval.html) - Fallback value for optional arguments
  - [quadrature](./stdlib_quadrature.html) - Numerical integration
  - [stats](./stdlib_stats.html) - Descriptive Statistics

From d1f143e830c68d848c3f602bd4a590acb975abff Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Mon, 16 Nov 2020 11:29:55 -0700
Subject: [PATCH 03/12] Documented changes in the stdlib_logger.f90 API

Documented changes in stdlib_logger.f90. Among them:
1. Additions of buffer and len_buffer to the logger type
2. Changes of self from intent(in) to intent(inout) in several procedures
3. Allowing new_line call in messsage string

[ticket: X]
---
 doc/specs/stdlib_logger.md | 58 +++++++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 23 deletions(-)

diff --git a/doc/specs/stdlib_logger.md b/doc/specs/stdlib_logger.md
index 83ed7f2cf..10d522a33 100644
--- a/doc/specs/stdlib_logger.md
+++ b/doc/specs/stdlib_logger.md
@@ -75,14 +75,16 @@ significant events encountered during the execution of a program.
 
 ### Private attributes
 
-| Attribute        | Type          | Description                                     | Initial value
-|------------------|---------------|-------------------------------------------------|--------------
-| `add_blank_line` | Logical       | Flag to precede output with a blank line        | `.false.`
-| `indent_lines`   | Logical       | Flag to indent subsequent lines by four columns | `.true.`
-| `log_units`      | Integer array | List of I/O units used for output               | empty
-| `max_width`      | Integer       | Maximum column width of output                  | 0
-| `time_stamp`     | Logical       | Flag to precede output by a time stamp          | `.true.`
-| `units`          | Integer       | Count of the number of active output units      | 0
+| Attribute        | Type          | Description                                     | Initial value |
+|------------------|---------------|-------------------------------------------------|--------------|
+| `add_blank_line` | Logical       | Flag to precede output with a blank line        | `.false.`    |
+|`buffer`          | Character(:)  | Buffer to build output string                   | Unallocated  |
+| `indent_lines`   | Logical       | Flag to indent subsequent lines by four columns | `.true.`     |
+| `len_buffer`     | Integer       | Number of valid characters in buffer            | 0            |
+| `log_units`      | Integer array | List of I/O units used for output               | Unallocated  |
+| `max_width`      | Integer       | Maximum column width of output                  | 0            |
+| `time_stamp`     | Logical       | Flag to precede output by a time stamp          | `.true.`     |
+| `units`          | Integer       | Count of the number of active output units      | 0            |
 
 ## The `stdlib_logger` variable
 
@@ -285,7 +287,7 @@ Pure subroutine
 
 #### Arguments
 
-`self`: shall be a scalar variable of type `logger_type`. It is an
+`self`: shall be a scalar expression of type `logger_type`. It is an
 `intent(in)` argument. It shall be the logger whose configuration is reported.
 
 `add_blank_line` (optional): shall be a scalar default logical
@@ -415,11 +417,13 @@ Subroutine
 
 #### Arguments
 
-`self`: shall be a scalar expression of type `logger_type`. It is an
-`intent(in)` argument. It is the logger used to send the message.
+`self`: shall be a scalar variable of type `logger_type`. It is an
+`intent(inout)` argument. It is the logger used to send the message.
 
 `message`: shall be a scalar default character expression. It is an
-  `intent(in)` argument.
+`intent(in)` argument.
+
+* Note `message` may have embedded new_line calls. 
 
 `module` (optional): shall be a scalar default character
   expression. It is an `intent(in)` argument. It should be the name of
@@ -496,12 +500,14 @@ Subroutine
 
 #### Arguments
 
-`self`: shall be a scalar expression of type `logger_type`. It is an
-`intent(in)` argument. It is the logger used to send the message.
+`self`: shall be a scalar variable of type `logger_type`. It is an
+`intent(inout)` argument. It is the logger used to send the message.
 
 `message`: shall be a scalar default character expression. It is an
   `intent(in)` argument.
 
+* Note `message` may have embedded new_line calls. 
+
 `module` (optional): shall be a scalar default character
   expression. It is an `intent(in)` argument. It should be the name of
   the module containing the `log_information` call.
@@ -565,12 +571,14 @@ written.
 Subroutine
 
 #### Arguments
-`self`: shall be a scalar expression of type `logger_type`. It is an
-`intent(in)` argument. It is the logger used to send the message.
+`self`: shall be a scalar variable of type `logger_type`. It is an
+`intent(inout)` argument. It is the logger used to send the message.
 
 `message`: shall be a scalar default character expression. It is an
   `intent(in)` argument.
 
+* Note `message` may have embedded new_line calls. 
+
 `module` (optional): shall be a scalar default character
   expression. It is an `intent(in)` argument. It should be the name of
   the module containing the `log_io_error` call.
@@ -641,12 +649,14 @@ Subroutine
 
 #### Arguments
 
-`self`: shall be a scalar expression of type `logger_type`. It is an
-`intent(in)` argument. It is the logger used to send the message.
+`self`: shall be a scalar variable of type `logger_type`. It is an
+`intent(inout)` argument. It is the logger used to send the message.
 
 `message`: shall be a scalar default character expression. It is an
   `intent(in)` argument.
 
+* Note `message` may have embedded new_line calls. 
+
 `module` (optional): shall be a scalar default character
   expression. It is an `intent(in)` argument. It should be the name of
   the module containing the `log_message` call.
@@ -715,8 +725,8 @@ Subroutine
 
 #### Arguments
 
-`self`: shall be a scalar expression of type `logger_type`. It is an
-`intent(in)` argument. It is the logger used to send the message.
+`self`: shall be a scalar variable of type `logger_type`. It is an
+`intent(inout)` argument. It is the logger used to send the message.
 
 `line`: shall be a scalar default character expression. It is an
   `intent(in)` argument. It should be the line of text in which the
@@ -861,12 +871,14 @@ Subroutine
 
 #### Arguments
 
-`self`: shall be a scalar expression of type `logger_type`. It is an
-`intent(in)` argument. It is the logger used to send the message.
+`self`: shall be a scalar variable of type `logger_type`. It is an
+`intent(inout)` argument. It is the logger used to send the message.
 
 `message`: shall be a scalar default character expression. It is an
   `intent(in)` argument.
 
+* Note `message` may have embedded new_line calls. 
+
 `module`: (optional) shall be a scalar default character
   expression. It is an `intent(in)` argument. It should be the name of
   the module containing the `log_warning` call.
@@ -924,7 +936,7 @@ Subroutine
 
 #### Arguments
 
-`self`: shall be a scalar expression of type `logger_type`. It is an
+`self`: shall be a scalar variable of type `logger_type`. It is an
 `intent(inout)` argument. It is the logger whose `log_units` is to be
 modified.
 

From 3fdcb73306c27e228622412e0a8b0ca043b8318a Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Mon, 16 Nov 2020 11:36:04 -0700
Subject: [PATCH 04/12] Typo fixes and thread/asynchronous IO safety.

Numerous changes to src/stdlib_logger.f90:
1. Changed `Rrea_...` to `read_...`
2. Shortened several long lines, mostly those longer than 80 characters
3. Added buffer and len_buffer to logger_type(?)
4. Changed output so that instead of multiple writes of individual strings there
   is a single write of a single string formatted by inserting new_line calls.

[ticket: X]
---
 src/stdlib_logger.f90 | 436 ++++++++++++++++++++++++------------------
 1 file changed, 248 insertions(+), 188 deletions(-)

diff --git a/src/stdlib_logger.f90 b/src/stdlib_logger.f90
index b67934460..8c43e4fd4 100644
--- a/src/stdlib_logger.f90
+++ b/src/stdlib_logger.f90
@@ -76,12 +76,14 @@ module stdlib_logger
         !! Public derived type ([Specification](../page/specs/stdlib_logger.html#the-derived-type-logger_type))
         private
 
-        logical              :: add_blank_line = .false.
-        logical              :: indent_lines = .true.
-        integer, allocatable :: log_units(:)
-        integer              :: max_width = 0
-        logical              :: time_stamp = .true.
-        integer              :: units = 0
+        logical                   :: add_blank_line = .false.
+        character(:), allocatable :: buffer
+        logical                   :: indent_lines = .true.
+        integer                   :: len_buffer = 0
+        integer, allocatable      :: log_units(:)
+        integer                   :: max_width = 0
+        logical                   :: time_stamp = .true.
+        integer                   :: units = 0
 
     contains
 
@@ -121,8 +123,8 @@ subroutine add_log_file( self, filename, unit, action, position, status, &
 !! array. `action`, if present, is the `action` specifier of the `open`
 !! statement, and has the default value of `"write"`. `position`, if present,
 !! is the `position` specifier, and has the default value of `"REWIND"`.
-!! `status`, if present, is the `status` specifier of the `open` statement, and
-!! has the default value of `"REPLACE"`. `stat`, if present, has the value
+!! `status`, if present, is the `status` specifier of the `open` statement,
+!! and has the default value of `"REPLACE"`. `stat`, if present, has the value
 !! `success` if `filename` could be opened, `read_only_error` if `action` is
 !! `"read"`, and `open_failure` otherwise.
 !!([Specification](../page/specs/stdlib_logger.html#add_log_file-open-a-file-and-add-its-unit-to-self-log_units))
@@ -141,7 +143,8 @@ subroutine add_log_file( self, filename, unit, action, position, status, &
         integer, intent(out), optional     :: stat
 !! The error status on exit with the possible values
 !! * `success` - no errors found
-!! * `Rrea_only_error` - file unopened as `action1 was `"read"` for an output file
+!! * `read_only_error` - file unopened as `action1 was `"read"` for an output
+!!   file
 !! * `open_failure` - the `open` statement failed
 
 
@@ -236,8 +239,8 @@ subroutine add_log_unit( self, unit, stat )
 !! version: experimental
 
 !! Adds `unit` to the log file units in `log_units`. `unit` must be an `open`
-!! file, of `form` `"formatted"`, with `"sequential"` `access`, and an `action` of
-!! `"write"` or `"readwrite"`, otherwise either `stat`, if preseent, has a
+!! file, of `form` `"formatted"`, with `"sequential"` `access`, and an `action`
+!! of `"write"` or `"readwrite"`, otherwise either `stat`, if preseent, has a
 !! value other than `success` and `unit` is not entered into `log_units`,
 !! or, if `stat` is not presecn, processing stops.
 !!([Specification](../page/specs/stdlib_logger.html#add_log_unit-add-a-unit-to-the-array-self-log_units))
@@ -263,7 +266,7 @@ subroutine add_log_unit( self, unit, stat )
 !!         integer :: iostat, unit, stat
 !!         ...
 !!         open( newunit=unit, 'error_log.txt', form='formatted', &
-!!               status='replace', position='rewind', err=999,  &
+!!               status='replace', position='rewind', err=999,    &
 !!               action='read', iostat=iostat, iomsg=iomsg )
 !!         ...
 !!         call global_logger % add_log_unit( unit, stat )
@@ -499,8 +502,8 @@ subroutine final_logger( self )
         do unit=1, self % units
             flush( self % log_units(unit), iomsg=message, iostat=iostat )
             if ( iostat /= 0 ) then
-                write(error_unit, '(a, i0)' ) 'In the logger_type finalizer ' // &
-                    'an error occurred in flushing unit = ',                     &
+                write(error_unit, '(a, i0)' ) 'In the logger_type ' // &
+                    'finalizer an error occurred in flushing unit = ', &
                     self % log_units(unit)
                 write(error_unit, '(a, i0)') 'With iostat = ', iostat
                 write(error_unit, '(a)') 'With iomsg = ' // trim(message)
@@ -510,23 +513,23 @@ subroutine final_logger( self )
     end subroutine final_logger
 
 
-    subroutine format_output_string( self, unit, string, procedure_name, &
-                                     col_indent )
+    subroutine format_output_string( self, string, col_indent )
 !! version: experimental
 
 !! Writes the STRING to UNIT ensuring that the number of characters
 !! does not exceed MAX_WIDTH and that the lines after the first
 !! one are indented four characters.
-        class(logger_type), intent(in) :: self
-        integer, intent(in)            :: unit
-        character(*), intent(in)       :: string
-        character(*), intent(in)       :: procedure_name
-        character(*), intent(in)       :: col_indent
+        class(logger_type), intent(inout) :: self
+        character(*), intent(in)          :: string
+        character(*), intent(in)          :: col_indent
 
         integer :: count, indent_len, index_, iostat, length, remain
         character(256) :: iomsg
+        integer, parameter :: new_len = len(new_line('a'))
 
         length = len_trim(string)
+        allocate( character(2*length) :: self % buffer )
+        self % len_buffer = 0
         indent_len = len(col_indent)
         call format_first_line()
 
@@ -544,16 +547,17 @@ subroutine format_output_string( self, unit, string, procedure_name, &
 
         subroutine format_first_line()
 
-            if ( self % max_width == 0 .or.                                         &
-                ( length <= self % max_width .and.                                  &
+            if ( self % max_width == 0 .or.                     &
+                ( length <= self % max_width .and.              &
                 index( string(1:length), new_line('a')) == 0 ) ) then
-                write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                    string(1:length)
+                self % buffer(1:length) = string(1:length)
+                self % len_buffer = length
                 remain = 0
                 return
             else
 
-                index_ = index( string(1:min(length, self % max_width)), new_line('a'))
+                index_ = index( string(1:min(length, self % max_width)), &
+                                new_line('a') )
                 if ( index_ == 0 ) then
                     do index_=self % max_width, 1, -1
                         if ( string(index_:index_) == ' ' ) exit
@@ -561,14 +565,15 @@ subroutine format_first_line()
                 end if
 
                 if ( index_ == 0 ) then
-                    write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
+                    self % buffer(1:self % max_width) = &
                         string(1:self % max_width)
+                    self % len_buffer = self % max_width
                     count = self % max_width
                     remain = length - count
                     return
                 else
-                    write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                        string(1:index_-1)
+                    self % buffer(1:index_-1) = string(1:index_-1)
+                    self % len_buffer = index_-1
                     count = index_
                     remain = length - count
                     return
@@ -576,21 +581,28 @@ subroutine format_first_line()
 
             end if
 
-999         call handle_write_failure( unit, procedure_name, iostat, iomsg )
-
         end subroutine format_first_line
 
         subroutine format_subsequent_line()
+            integer :: new_len_buffer
+            character(:), allocatable :: dummy
 
             if ( remain <= self % max_width ) then
-                write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                    string(count+1:length)
+                new_len_buffer = self % len_buffer + length - count + new_len
+                if ( new_len_buffer > len( self % buffer ) ) then
+                    allocate( character( 2*len( self % buffer ) ) :: dummy )
+                    dummy = self % buffer
+                    call move_alloc( dummy, self % buffer )
+                end if
+                self % buffer( self % len_buffer+1:new_len_buffer ) = &
+                    new_line('a') // string(count+1:length)
+                self % len_buffer = new_len_buffer
                 count = length
                 remain = 0
                 return
             else
 
-                index_ = count + index( string(count+1:count+self % max_width), &
+                index_ = count + index(string(count+1:count+self % max_width),&
                     new_line('a'))
                 if(index_ == count) then
                     do index_=count+self % max_width, count+1, -1
@@ -599,14 +611,30 @@ subroutine format_subsequent_line()
                 end if
 
                 if ( index_ == count ) then
-                    write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                        string(count+1:count+self % max_width)
+                    new_len_buffer = self % len_buffer + self % max_width + &
+                        new_len
+                    if ( new_len_buffer > len( self % buffer ) ) then
+                        allocate( character( 2*len( self % buffer ) ) :: dummy )
+                        dummy = self % buffer
+                        call move_alloc( dummy, self % buffer )
+                    end if
+                    self % buffer( self % len_buffer+1:new_len_buffer ) = &
+                        new_line('a') // string(count+1:count+self % max_width)
+                    self % len_buffer = new_len_buffer
                     count = count + self % max_width
                     remain = length - count
                     return
                 else
-                    write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                        string(count+1:index_-1)
+                    new_len_buffer = self % len_buffer + index_ - 1 &
+                        - count + new_len
+                    if ( new_len_buffer > len( self % buffer ) ) then
+                        allocate( character( 2*len( self % buffer ) ) :: dummy )
+                        dummy = self % buffer
+                        call move_alloc( dummy, self % buffer )
+                    end if
+                    self % buffer( self % len_buffer+1:new_len_buffer ) = &
+                        new_line('a') // string(count+1:index_-1)
+                    self % len_buffer = new_len_buffer
                     count = index_
                     remain = length - count
                     return
@@ -614,16 +642,26 @@ subroutine format_subsequent_line()
 
             end if
 
-999         call handle_write_failure( unit, procedure_name, iostat, iomsg )
-
         end subroutine format_subsequent_line
 
         subroutine indent_format_subsequent_line()
+            integer :: new_len_buffer
+            character(:), allocatable :: dummy
 
             if ( index( string(count+1:length), new_line('a')) == 0 .and. &
                 remain <= self % max_width - indent_len ) then
-                write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                    col_indent // string(count+1:length)
+                new_len_buffer = self % len_buffer + index_ - 1 &
+                    - count + new_len + indent_len
+                if ( new_len_buffer > len( self % buffer ) ) then
+                    allocate( character( 2*len( self % buffer ) ) :: dummy )
+                    dummy = self % buffer
+                    call move_alloc( dummy, self % buffer )
+                end if
+                self % buffer( self % len_buffer+1: &
+                    self % len_buffer + length - count + new_len &
+                    + indent_len ) = &
+                    new_line('a') // col_indent // string(count+1:index_-1)
+                self % len_buffer = new_len_buffer
                 count = length
                 remain = 0
                 return
@@ -639,15 +677,31 @@ subroutine indent_format_subsequent_line()
                 end if
 
                 if ( index_ == count ) then
-                    write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                        col_indent //                                         &
+                    new_len_buffer = self % len_buffer + self % max_width &
+                        + new_len 
+                    if ( new_len_buffer > len( self % buffer ) ) then
+                        allocate( character( 2*len( self % buffer ) ) :: dummy )
+                        dummy = self % buffer
+                        call move_alloc( dummy, self % buffer )
+                    end if
+                    self % buffer( self % len_buffer+1: new_len_buffer ) = &
+                        new_line('a') // col_indent // &
                         string(count+1:count+self % max_width-indent_len)
+                    self % len_buffer = new_len_buffer
                     count = count + self % max_width - indent_len
                     remain = length - count
                     return
                 else
-                    write( unit, '(a)', err=999, iostat=iostat, iomsg=iomsg ) &
-                        col_indent // string(count+1:index_-1)
+                    new_len_buffer = self % len_buffer + index_ - count - 1 &
+                        + new_len + indent_len
+                    if ( new_len_buffer > len( self % buffer ) ) then
+                        allocate( character( 2*len( self % buffer ) ) :: dummy )
+                        dummy = self % buffer
+                        call move_alloc( dummy, self % buffer )
+                    end if
+                    self % buffer( self % len_buffer+1: new_len_buffer ) = &
+                        new_line('a') // col_indent // string(count+1:index_-1)
+                    self % len_buffer = new_len_buffer
                     count = index_
                     remain = length - count
                     return
@@ -655,8 +709,6 @@ subroutine indent_format_subsequent_line()
 
             end if
 
-999         call handle_write_failure( unit, procedure_name, iostat, iomsg )
-
         end subroutine indent_format_subsequent_line
 
     end subroutine format_output_string
@@ -679,18 +731,22 @@ subroutine handle_write_failure( unit, procedure_name, iostat, iomsg )
 
          write( output_unit, '(a)' ) 'write failure in ' // module_name // &
              ' % ' // trim(procedure_name) // '.'
-         write( output_unit, '(a, i0)' ) 'unit = ', unit
-         inquire( unit, named=named )
-
-         if ( named ) then
-             inquire( unit, name=name )
-             write( output_unit, '(a, a)' ) 'name = ', trim(name)
+         if ( unit == -999 ) then
+             write( output_unit, '(a, i0)' ) 'unit = internal file'
          else
-             write( output_unit, '(a)' ) 'unit is unnamed'
+             write( output_unit, '(a, i0)' ) 'unit = ', unit
+             inquire( unit, named=named )
+
+             if ( named ) then
+                 inquire( unit, name=name )
+                 write( output_unit, '(a, a)' ) 'name = ', trim(name)
+             else
+                 write( output_unit, '(a)' ) 'unit is unnamed'
+             end if
+             inquire( unit, action=action )
+             write( output_unit, '(a, a)' ) 'action = ', trim(action)
          end if
 
-         inquire( unit, action=action )
-         write( output_unit, '(a, a)' ) 'action = ', trim(action)
          write( output_unit, '(a, i0)' ) 'iostat = ', iostat
          write( output_unit, '(a, a )' ) 'iomsg = ', trim(iomsg)
          error stop 'write failure in ' // module_name // '.'
@@ -742,7 +798,7 @@ subroutine log_error( self, message, module, procedure, stat, errmsg )
 !!     end module example_mod
 !!
 
-        class(logger_type), intent(in)          :: self
+        class(logger_type), intent(inout)       :: self
 !! The logger to be used in logging the message
         character(len=*), intent(in)            :: message
 !! A string to be written to log_unit
@@ -758,46 +814,29 @@ subroutine log_error( self, message, module, procedure, stat, errmsg )
         integer :: unit
         integer :: iostat
         character(*), parameter :: procedure_name = 'log_error'
-        character(256) :: iomsg
-
-        call self % log_message( message,               &
-                                 module = module,       &
-                                 procedure = procedure, &
-                                 prefix = 'ERROR')
+        character(256) :: iomsg, suffix
 
-        if ( self % units == 0 ) then
-            call write_log_error( output_unit )
-        else
-            do unit=1, self % units
-                call write_log_error( self % log_units(unit) )
-            end do
+        if ( present(stat) ) then
+            write( suffix, '(a, i0)', err=999, iostat=iostat, iomsg=iomsg ) &
+                new_line('a') // "With stat = ", stat
         end if
 
-    contains
-
-        subroutine write_log_error( unit )
-            integer, intent(in) :: unit
-
-            if ( present(stat) ) then
-                write( unit, '("With stat = ", i0)', err=999, &
-                    iostat=iostat, iomsg=iomsg ) stat
-            end if
-
-            if ( present(errmsg) ) then
-                if ( len_trim(errmsg) > 0 ) then
-                    call format_output_string( self, unit,          &
-                                               'With errmsg = "' // &
-                                               trim(errmsg) // '"', &
-                                               procedure_name,      &
-                                               '    ' )
-                end if
+        if ( present(errmsg) ) then
+            if ( len_trim(errmsg) > 0 ) then
+                suffix( len_trim(suffix)+1: ) = &
+                    new_line('a') // 'With errmsg = "' // trim(errmsg) // '"'
             end if
+        end if
 
-            return
+        call self % log_message( trim(message) // trim(suffix), &
+                                 module = module,               &
+                                 procedure = procedure,         &
+                                 prefix = 'ERROR')
 
-999         call handle_write_failure( unit, procedure_name, iostat, iomsg )
+        return
 
-        end subroutine write_log_error
+        unit = -999
+999     call handle_write_failure( unit, procedure_name, iostat, iomsg )
 
     end subroutine log_error
 
@@ -842,14 +881,15 @@ subroutine log_information( self, message, module, procedure )
 !!     end module example_mod
 !!
 
-        class(logger_type), intent(in)          :: self
+        class(logger_type), intent(inout)       :: self
 !! The logger used to send the message
         character(len=*), intent(in)            :: message
 !! A string to be written to log_unit
         character(len=*), intent(in), optional  :: module
 !! The name of the module contining the current invocation of `log_information`
         character(len=*), intent(in), optional  :: procedure
-!! The name of the procedure contining the current invocation of `log_information`
+!! The name of the procedure contining the current invocation of
+!! `log_information`
 
         call self % log_message( message,               &
                                  module = module,       &
@@ -894,7 +934,7 @@ subroutine log_io_error( self, message, module, procedure, iostat, &
 !!      ...
 !!    end program example
 
-        class(logger_type), intent(in)          :: self
+        class(logger_type), intent(inout)       :: self
 !! The logger variable to receivee the message
         character(len=*), intent(in)            :: message
 !! A string to be written to LOG_UNIT
@@ -910,46 +950,29 @@ subroutine log_io_error( self, message, module, procedure, iostat, &
         integer :: unit
         integer :: iostat2
         character(*), parameter :: procedure_name = 'log_error'
-        character(256) :: iomsg2
+        character(256) :: iomsg2, suffix
 
-        call self % log_message( message,               &
-                                 module = module,       &
-                                 procedure = procedure, &
-                                 prefix = 'I/O ERROR' )
-
-        if ( self % units == 0 ) then
-            call write_log_io_error( output_unit )
-        else
-            do unit=1, self % units
-                call write_log_io_error( self % log_units(unit) )
-            end do
+        if ( present(iostat) ) then
+            write( suffix, '(a, i0)', err=999, iostat=iostat2, iomsg=iomsg2 ) &
+                new_line('a') // "With iostat = ", iostat
         end if
 
-    contains
-
-        subroutine write_log_io_error( unit )
-            integer, intent(in) :: unit
-
-            if ( present(iostat) ) then
-                write( unit, '("With iostat = ", i0)', err=999, &
-                    iostat=iostat2, iomsg=iomsg2 ) iostat
-            end if
-
-            if ( present(iomsg) ) then
-                if ( len_trim(iomsg) > 0 ) then
-                    call format_output_string( self,  unit,        &
-                                               'With iomsg = "' // &
-                                               trim(iomsg) // '"', &
-                                               procedure_name,     &
-                                               '    ' )
-                end if
+        if ( present(iomsg) ) then
+            if ( len_trim(iomsg) > 0 ) then
+                suffix( len_trim(suffix)+1: ) = &
+                    new_line('a') // 'With iomsg = "' // trim(iomsg) // '"'
             end if
+        end if
 
-            return
+        call self % log_message( trim(message) // trim(suffix), &
+                                 module = module,               &
+                                 procedure = procedure,         &
+                                 prefix = 'I/O ERROR' )
 
-999         call handle_write_failure( unit, procedure_name, iostat, iomsg )
+        return
 
-        end subroutine write_log_io_error
+        unit = -999
+999     call handle_write_failure( unit, procedure_name, iostat, iomsg )
 
     end subroutine log_io_error
 
@@ -991,7 +1014,7 @@ subroutine log_message( self, message, module, procedure, prefix )
 !!    end module example_mod
 !!
 
-        class(logger_type), intent(in)          :: self
+        class(logger_type), intent(inout)       :: self
 !! The logger variable to receive the message
         character(len=*), intent(in)            :: message
 !! A string to be written to log_unit
@@ -1032,32 +1055,43 @@ subroutine log_message( self, message, module, procedure, prefix )
             m_and_p = ''
         end if
 
+        call format_output_string( self,                         &
+                                   d_and_t // m_and_p // pref // &
+                                   trim( message ),              &
+                                   '    ' )
+
         if ( self % units == 0 ) then
-            call write_log_message( output_unit )
+            if ( self % add_blank_line ) then
+                write( output_unit, '(a)', err=999, iostat=iostat, &
+                        iomsg=iomsg) &
+                    new_line('a') // self % buffer(0:self % len_buffer)
+            else
+                write( output_unit, '(a)', err=999, iostat=iostat, &
+                        iomsg=iomsg ) &
+                    self % buffer(0:self % len_buffer)
+            end if
         else
-            do unit=1, self % units
-                call write_log_message( self % log_units(unit) )
-            end do
+            if ( self % add_blank_line ) then
+                do unit=1, self % units
+                    write( output_unit, '(a)', err=999, iostat=iostat, &
+                        iomsg=iomsg ) &
+                        new_line('a') // self % buffer(0:self % len_buffer)
+                end do
+            else
+                do unit=1, self % units
+                    write( output_unit, '(a)', err=999, iostat=iostat, &
+                        iomsg=iomsg ) &
+                        self % buffer(0:self % len_buffer)
+                end do
+            end if
         end if
 
-    contains
-
-        subroutine write_log_message( unit )
-            integer, intent(in) :: unit
-
-            if ( self % add_blank_line ) write( unit, *, err=999, &
-                iostat=iostat, iomsg=iomsg )
-
-            call format_output_string( self, unit,                   &
-                                       d_and_t // m_and_p // pref // &
-                                       trim( message ),              &
-                                       procedure_name, '    ' )
+        deallocate( self % buffer )
+        self % len_buffer = 0
 
-            return
-
-999         call handle_write_failure( unit, procedure_name, iostat, iomsg )
+        return
 
-        end subroutine write_log_message
+999     call handle_write_failure( unit, procedure_name, iostat, iomsg )
 
     end subroutine log_message
 
@@ -1073,8 +1107,8 @@ subroutine log_text_error( self, line, column, summary, filename,  &
 !!
 !! If time stamps are active first a time stamp is written. Then if
 !! `filename` or `line_number` or `column` are present they are written.
-!! Then `line` is written. Then the symbol `caret` is written below `line` at the
-!! column indicated by `column`. Then `summary` is written.
+!! Then `line` is written. Then the symbol `caret` is written below `line`
+!! at the column indicated by `column`. Then `summary` is written.
 !
 !!##### Example
 !!
@@ -1102,7 +1136,7 @@ subroutine log_text_error( self, line, column, summary, filename,  &
 !!      ...
 !!    end program example
 !!
-        class(logger_type), intent(in)        :: self
+        class(logger_type), intent(inout)     :: self
 !! The logger variable to receive the message
         character(*), intent(in)              :: line
 !! The line of text in which the error was found.
@@ -1119,8 +1153,8 @@ subroutine log_text_error( self, line, column, summary, filename,  &
         integer, intent(out), optional        :: stat
 !! Integer flag that an error has occurred. Has the value `success` if no
 !! error hass occurred, `index_invalid_error` if `column` is less than zero or
-!! greater than `len(line)`, and `write_failure` if any of the `write` statements
-!! has failed.
+!! greater than `len(line)`, and `write_failure` if any of the `write`
+!! statements has failed.
 
         character(1)              :: acaret
         character(5)              :: num
@@ -1145,57 +1179,84 @@ subroutine log_text_error( self, line, column, summary, filename,  &
             end if
         end if
 
-        write(num, '(i0)') column-1
-        fmt = '(' // trim(num) // 'x, a)'
-
+        call write_log_text_error_buffer( )
         if ( self % units == 0 ) then
-            call write_log_text_error( output_unit )
+            write( output_unit, '(a)' ) self % buffer
         else
             do lun=1, self % units
-                call write_log_text_error( self % log_units(lun) )
-
+                write( self % log_units(lun), '(a)' ) self % buffer
             end do
         end if
+        deallocate( self % buffer )
+        self % len_buffer = 0
 
     contains
 
-        subroutine write_log_text_error( unit )
-            integer, intent(in) :: unit
-
-            if ( self % add_blank_line ) write( unit, * )
-
-            if ( self % time_stamp ) write( unit, '(a)' ) time_stamp()
+        subroutine write_log_text_error_buffer( )
+            integer                   :: i
+            character(:), allocatable :: location, marker
 
             if ( present(filename) ) then
                 if ( present(line_number) ) then
-                    write( unit, '(a,":", i0, ":", i0)', err=999, &
+                    allocate( character(len_trim(filename)+15) :: location )
+                    write( location, fmt='(a, ":", i0, ":", i0)', err=999, &
                            iomsg=iomsg, iostat=iostat )           &
                            trim(filename) , line_number, column
                 else
-                    write( unit, '(a, i0)', err=999, iomsg=iomsg, &
+                    allocate( character(len_trim(filename)+45) :: location )
+                    write( location, fmt='(a, i0)', err=999, iomsg=iomsg, &
                            iostat=iostat ) &
-                           "Error found in file: '" // trim(filename) // "'" &
-                           // ', at column: ', column
+                           "Error found in file: '" // trim(filename) // &
+                           "', at column: ", column
                 end if
 
             else
                 if ( present(line_number) ) then
-                    write( unit, '(a, i0, a, i0)', err=999, iomsg=iomsg, &
-                           iostat=iostat ) &
+                    allocate( character(54) :: location )
+                    write( location, fmt='(a, i0, a, i0)', err=999, &
+                           iomsg=iomsg, iostat=iostat ) &
                         'Error found at line number: ', line_number, &
                         ', and column: ', column
                 else
-                    write( unit, '("Error found in line at column:", i0)' ) &
+                    allocate( character(36) :: location )
+                    write( location, &
+                           fmt='("Error found in line at column:", i0)' ) &
                         column
                 end if
             end if
 
-            write( unit, * )
-            write( unit, '(a)', err=999, iomsg=iomsg, iostat=iostat ) line
-            write( unit, fmt, err=999, iomsg=iomsg, iostat=iostat ) &
-                acaret
-            write( unit, '(a)', err=999, iomsg=iomsg, iostat=iostat ) &
-                'Error: ' // trim(summary)
+            allocate( character(column) :: marker )
+            do i=1, column-1
+                marker(i:i) = ' '
+            end do
+            marker(column:column) = acaret
+            if ( self % add_blank_line ) then
+                if ( self % time_stamp ) then
+                    self % buffer = new_line('a') // time_stamp() // &
+                        new_line('a') // trim(location) // &
+                        new_line('a') // new_line('a') // trim(line) // &
+                        new_line('a') // marker // &
+                        new_line('a') // 'Error: ' // trim(summary)
+                else
+                    self % buffer = new_line('a') // trim(location) // &
+                        new_line('a') // new_line('a') // trim(line) // &
+                        new_line('a') // marker // &
+                        new_line('a') // 'Error: ' // trim(summary)
+                end if
+            else
+                if ( self % time_stamp ) then
+                    self % buffer = time_stamp() // &
+                        new_line('a') // trim(location) // &
+                        new_line('a') // new_line('a') // trim(line) // &
+                        new_line('a') // marker // &
+                        new_line('a') // 'Error: ' // trim(summary)
+                else
+                    self % buffer = trim(location) // &
+                        new_line('a') // new_line('a') // trim(line) // &
+                        new_line('a') // marker // &
+                        new_line('a') // 'Error: ' // trim(summary)
+                end if
+            end if
 
             if ( present(stat) ) stat = success
 
@@ -1204,14 +1265,12 @@ subroutine write_log_text_error( unit )
 999         if ( present( stat ) ) then
                 stat = write_failure
                 return
-
             else
-                call handle_write_failure( unit, procedure_name, iostat, &
+                call handle_write_failure( -999, procedure_name, iostat, &
                                            iomsg )
-
             end if
 
-        end subroutine write_log_text_error
+        end subroutine write_log_text_error_buffer
 
     end subroutine log_text_error
 
@@ -1255,7 +1314,8 @@ end function log_units_assigned
     subroutine log_warning( self, message, module, procedure )
 !! version: experimental
 
-!! Writes the string `message` to `self % log_units` with optional additional text.
+!! Writes the string `message` to `self % log_units` with optional additional
+!! text.
 !!([Specification](../page/specs/stdlib_logger.html#log_warning-write-the-string-message-to-log_units))
 
 !!##### Behavior
@@ -1290,7 +1350,7 @@ subroutine log_warning( self, message, module, procedure )
 !!       ...
 !!     end module example_mod
 !!
-        class(logger_type), intent(in)          :: self
+        class(logger_type), intent(inout)       :: self
 !! The logger to which the message is written
         character(len=*), intent(in)            :: message
 !! A string to be written to LOG_UNIT
@@ -1312,10 +1372,10 @@ subroutine remove_log_unit( self, unit, close_unit, stat )
 
 !! Remove the I/O unit from the self % log_units list. If `close_unit` is
 !! present and `.true.` then the corresponding file is closed. If `unit` is
-!! not in `log_units` then nothing is done. If `stat` is present it, by default,
-!! has the value `success`. If closing the `unit` fails, then if `stat` is
-!! present it has the value `close_failure`, otherwise processing stops
-!! with an informative message.
+!! not in `log_units` then nothing is done. If `stat` is present it, by
+!! default, has the value `success`. If closing the `unit` fails, then if
+!! `stat` is present it has the value `close_failure`, otherwise processing
+!! stops with an informative message.
 !!([Specification](../page/specs/stdlib_logger.html#remove_log_unit-remove-unit-from-self-log_units))
 
         class(logger_type), intent(inout) :: self

From 786aaa400c40ea4809b42e8b5d9928db29287c62 Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Mon, 16 Nov 2020 13:25:07 -0700
Subject: [PATCH 05/12] Fixed indexing and unused variables

Changed indexing of the self % buffer from 0 based to the proper 1s based, and
eliminated some unused variables.

[ticket: X]
---
 src/stdlib_logger.f90 | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/stdlib_logger.f90 b/src/stdlib_logger.f90
index 8c43e4fd4..3c364e755 100644
--- a/src/stdlib_logger.f90
+++ b/src/stdlib_logger.f90
@@ -523,8 +523,7 @@ subroutine format_output_string( self, string, col_indent )
         character(*), intent(in)          :: string
         character(*), intent(in)          :: col_indent
 
-        integer :: count, indent_len, index_, iostat, length, remain
-        character(256) :: iomsg
+        integer :: count, indent_len, index_, length, remain
         integer, parameter :: new_len = len(new_line('a'))
 
         length = len_trim(string)
@@ -1064,24 +1063,24 @@ subroutine log_message( self, message, module, procedure, prefix )
             if ( self % add_blank_line ) then
                 write( output_unit, '(a)', err=999, iostat=iostat, &
                         iomsg=iomsg) &
-                    new_line('a') // self % buffer(0:self % len_buffer)
+                    new_line('a') // self % buffer(1:self % len_buffer)
             else
                 write( output_unit, '(a)', err=999, iostat=iostat, &
                         iomsg=iomsg ) &
-                    self % buffer(0:self % len_buffer)
+                    self % buffer(1:self % len_buffer)
             end if
         else
             if ( self % add_blank_line ) then
                 do unit=1, self % units
                     write( output_unit, '(a)', err=999, iostat=iostat, &
-                        iomsg=iomsg ) &
-                        new_line('a') // self % buffer(0:self % len_buffer)
+                        iomsg=iomsg ) new_line('a') // &
+                        self % buffer(1:self % len_buffer)
                 end do
             else
                 do unit=1, self % units
                     write( output_unit, '(a)', err=999, iostat=iostat, &
                         iomsg=iomsg ) &
-                        self % buffer(0:self % len_buffer)
+                        self % buffer(1:self % len_buffer)
                 end do
             end if
         end if
@@ -1157,8 +1156,6 @@ subroutine log_text_error( self, line, column, summary, filename,  &
 !! statements has failed.
 
         character(1)              :: acaret
-        character(5)              :: num
-        character(:), allocatable :: fmt
         character(128)            :: iomsg
         integer                   :: iostat
         integer                   :: lun

From 0b1775479916f3c057606b64cbbf28fa17d493db Mon Sep 17 00:00:00 2001
From: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>
Date: Tue, 17 Nov 2020 16:28:10 +0100
Subject: [PATCH 06/12] Update src/stdlib_logger.f90

Co-authored-by: Ian Giestas Pauli <iangiestaspauli@gmail.com>
---
 src/stdlib_logger.f90 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/stdlib_logger.f90 b/src/stdlib_logger.f90
index 3c364e755..5350c0067 100644
--- a/src/stdlib_logger.f90
+++ b/src/stdlib_logger.f90
@@ -240,7 +240,7 @@ subroutine add_log_unit( self, unit, stat )
 
 !! Adds `unit` to the log file units in `log_units`. `unit` must be an `open`
 !! file, of `form` `"formatted"`, with `"sequential"` `access`, and an `action`
-!! of `"write"` or `"readwrite"`, otherwise either `stat`, if preseent, has a
+!! of `"write"` or `"readwrite"`, otherwise either `stat`, if present, has a
 !! value other than `success` and `unit` is not entered into `log_units`,
 !! or, if `stat` is not presecn, processing stops.
 !!([Specification](../page/specs/stdlib_logger.html#add_log_unit-add-a-unit-to-the-array-self-log_units))

From 42f60dfc1636c56491bc0d2290037350632a1fce Mon Sep 17 00:00:00 2001
From: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>
Date: Tue, 17 Nov 2020 16:42:54 +0100
Subject: [PATCH 07/12] Update doc/specs/stdlib_logger.md

---
 doc/specs/stdlib_logger.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/specs/stdlib_logger.md b/doc/specs/stdlib_logger.md
index 10d522a33..d2d6bf5a3 100644
--- a/doc/specs/stdlib_logger.md
+++ b/doc/specs/stdlib_logger.md
@@ -78,7 +78,7 @@ significant events encountered during the execution of a program.
 | Attribute        | Type          | Description                                     | Initial value |
 |------------------|---------------|-------------------------------------------------|--------------|
 | `add_blank_line` | Logical       | Flag to precede output with a blank line        | `.false.`    |
-|`buffer`          | Character(:)  | Buffer to build output string                   | Unallocated  |
+| `buffer`         | Character(:)  | Buffer to build output string                   | Unallocated  |
 | `indent_lines`   | Logical       | Flag to indent subsequent lines by four columns | `.true.`     |
 | `len_buffer`     | Integer       | Number of valid characters in buffer            | 0            |
 | `log_units`      | Integer array | List of I/O units used for output               | Unallocated  |

From 92cfe4c6ebb8974d5a983f735aca9cce3cc003e1 Mon Sep 17 00:00:00 2001
From: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>
Date: Tue, 17 Nov 2020 18:05:50 +0100
Subject: [PATCH 08/12] Apply suggestions from code review

---
 src/stdlib_logger.f90 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/stdlib_logger.f90 b/src/stdlib_logger.f90
index 5350c0067..facff89f4 100644
--- a/src/stdlib_logger.f90
+++ b/src/stdlib_logger.f90
@@ -1072,13 +1072,13 @@ subroutine log_message( self, message, module, procedure, prefix )
         else
             if ( self % add_blank_line ) then
                 do unit=1, self % units
-                    write( output_unit, '(a)', err=999, iostat=iostat, &
+                    write( self % log_units(unit), '(a)', err=999, iostat=iostat, &
                         iomsg=iomsg ) new_line('a') // &
                         self % buffer(1:self % len_buffer)
                 end do
             else
                 do unit=1, self % units
-                    write( output_unit, '(a)', err=999, iostat=iostat, &
+                    write( self % log_units(unit), '(a)', err=999, iostat=iostat, &
                         iomsg=iomsg ) &
                         self % buffer(1:self % len_buffer)
                 end do

From 0b95dbba9591a2639579096ac74f4ee85c9d3b33 Mon Sep 17 00:00:00 2001
From: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>
Date: Tue, 17 Nov 2020 22:05:33 +0100
Subject: [PATCH 09/12] Apply suggestions from code review

---
 src/stdlib_logger.f90 | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/stdlib_logger.f90 b/src/stdlib_logger.f90
index facff89f4..c9c7ea642 100644
--- a/src/stdlib_logger.f90
+++ b/src/stdlib_logger.f90
@@ -649,17 +649,15 @@ subroutine indent_format_subsequent_line()
 
             if ( index( string(count+1:length), new_line('a')) == 0 .and. &
                 remain <= self % max_width - indent_len ) then
-                new_len_buffer = self % len_buffer + index_ - 1 &
+                new_len_buffer = self % len_buffer + length &
                     - count + new_len + indent_len
                 if ( new_len_buffer > len( self % buffer ) ) then
                     allocate( character( 2*len( self % buffer ) ) :: dummy )
                     dummy = self % buffer
                     call move_alloc( dummy, self % buffer )
                 end if
-                self % buffer( self % len_buffer+1: &
-                    self % len_buffer + length - count + new_len &
-                    + indent_len ) = &
-                    new_line('a') // col_indent // string(count+1:index_-1)
+                self % buffer( self % len_buffer+1:new_len_buffer ) = &
+                    new_line('a') // col_indent // string(count+1:length)
                 self % len_buffer = new_len_buffer
                 count = length
                 remain = 0

From 5e68920b9f15331078307ac660245b5c80f2eb7d Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Tue, 17 Nov 2020 16:54:14 -0700
Subject: [PATCH 10/12] Fixed up log_error and log_io_error

Changed log_error and log_io_error similarly
1. Added dummy character variable of len 28 and used it to hold stat/iostat string
representation or lack thereof.
2. Changed suffix to allocatable len character variable and used it to hold the
combined stat/iostat and errmsg/iomsg string representations or lack thereof.
3. Eliminated the trim of suffix as unneeded.
4. Eliminated unit and passed -999 directly to handle_write_failure.
5. For log_io_error changed procedure_name to 'log_io_error'.

[ticket: X]
---
 src/stdlib_logger.f90 | 50 +++++++++++++++++++++++++++----------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/src/stdlib_logger.f90 b/src/stdlib_logger.f90
index c9c7ea642..0cb0d8dd3 100644
--- a/src/stdlib_logger.f90
+++ b/src/stdlib_logger.f90
@@ -808,32 +808,38 @@ subroutine log_error( self, message, module, procedure, stat, errmsg )
         character(len=*), intent(in), optional  :: errmsg
 !! The value of the `errmsg` specifier returned by a Fortran statement
 
-        integer :: unit
         integer :: iostat
+        character(28) :: dummy
+        character(256) :: iomsg
         character(*), parameter :: procedure_name = 'log_error'
-        character(256) :: iomsg, suffix
+        character(:), allocatable :: suffix
 
         if ( present(stat) ) then
-            write( suffix, '(a, i0)', err=999, iostat=iostat, iomsg=iomsg ) &
+            write( dummy, '(a, i0)', err=999, iostat=iostat, iomsg=iomsg ) &
                 new_line('a') // "With stat = ", stat
+        else
+            dummy = ' '
         end if
 
         if ( present(errmsg) ) then
             if ( len_trim(errmsg) > 0 ) then
-                suffix( len_trim(suffix)+1: ) = &
+                suffix = trim(dummy) // &
                     new_line('a') // 'With errmsg = "' // trim(errmsg) // '"'
+            else
+                suffix = dummy
             end if
+        else
+            suffix = dummy
         end if
 
-        call self % log_message( trim(message) // trim(suffix), &
-                                 module = module,               &
-                                 procedure = procedure,         &
+        call self % log_message( trim(message) // suffix, &
+                                 module = module,         &
+                                 procedure = procedure,   &
                                  prefix = 'ERROR')
 
         return
 
-        unit = -999
-999     call handle_write_failure( unit, procedure_name, iostat, iomsg )
+999     call handle_write_failure( -999, procedure_name, iostat, iomsg )
 
     end subroutine log_error
 
@@ -944,32 +950,38 @@ subroutine log_io_error( self, message, module, procedure, iostat, &
         character(len=*), intent(in), optional  :: iomsg
 !! The value of the IOMSG specifier returned by a Fortran I/O statement
 
-        integer :: unit
+        character(28) :: dummy
+        character(256) :: iomsg2
         integer :: iostat2
-        character(*), parameter :: procedure_name = 'log_error'
-        character(256) :: iomsg2, suffix
+        character(*), parameter :: procedure_name = 'log_io_error'
+        character(:), allocatable :: suffix
 
         if ( present(iostat) ) then
-            write( suffix, '(a, i0)', err=999, iostat=iostat2, iomsg=iomsg2 ) &
+            write( dummy, '(a, i0)', err=999, iostat=iostat2, iomsg=iomsg2 ) &
                 new_line('a') // "With iostat = ", iostat
+        else
+            dummy = ' '
         end if
 
         if ( present(iomsg) ) then
             if ( len_trim(iomsg) > 0 ) then
-                suffix( len_trim(suffix)+1: ) = &
+                suffix = trim(dummy) // &
                     new_line('a') // 'With iomsg = "' // trim(iomsg) // '"'
+            else
+                suffix = trim(dummy)
             end if
+        else
+            suffix = trim(dummy)
         end if
 
-        call self % log_message( trim(message) // trim(suffix), &
-                                 module = module,               &
-                                 procedure = procedure,         &
+        call self % log_message( trim(message) // suffix, &
+                                 module = module,         &
+                                 procedure = procedure,   &
                                  prefix = 'I/O ERROR' )
 
         return
 
-        unit = -999
-999     call handle_write_failure( unit, procedure_name, iostat, iomsg )
+999     call handle_write_failure( -999, procedure_name, iostat2, iomsg2 )
 
     end subroutine log_io_error
 

From 0853039d3e4e75f2931a7b39945f211d39003854 Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Mon, 23 Nov 2020 17:32:39 -0700
Subject: [PATCH 11/12] Documented attempt to make code thread and asynchronous
 I/O safe

Added the sentence "While every effort has been made to make the code thread and
asynchronous I/O safe, it is always best to have each process write to
its own dedicated logger file."

[ticket: X]
---
 doc/specs/stdlib_logger.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/doc/specs/stdlib_logger.md b/doc/specs/stdlib_logger.md
index d2d6bf5a3..c9e4b154b 100644
--- a/doc/specs/stdlib_logger.md
+++ b/doc/specs/stdlib_logger.md
@@ -34,6 +34,10 @@ The logger variables have the option to:
 * indent subsequent lines of the messages; and
 * format the text to fit within a maximum column width.
 
+While every effort has been made to make the code thread and
+asynchronous I/O safe, it is always best to have each process write to
+its own dedicated logger file.
+
 Note: Loggers of type `logger_type` normally report their messages to I/O
 units in the internal list termed `log_units`. However if `log_units`
 is empty then the messages go to the `output_unit` of the intrinsic

From 381c3fe19f1cdcfe8c0fb6f81bbb6c36dce1b2b3 Mon Sep 17 00:00:00 2001
From: William Clodius <w.clodius@icloud.com>
Date: Tue, 24 Nov 2020 09:52:09 -0700
Subject: [PATCH 12/12] Revised discussion of thread safety

Added Jeremies revision of the discussion in stdlib_logger.md.

[ticket: X]
---
 doc/specs/stdlib_logger.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/doc/specs/stdlib_logger.md b/doc/specs/stdlib_logger.md
index c9e4b154b..68b9927a1 100644
--- a/doc/specs/stdlib_logger.md
+++ b/doc/specs/stdlib_logger.md
@@ -34,9 +34,11 @@ The logger variables have the option to:
 * indent subsequent lines of the messages; and
 * format the text to fit within a maximum column width.
 
-While every effort has been made to make the code thread and
+While every effort has been made to make the code process and
 asynchronous I/O safe, it is always best to have each process write to
 its own dedicated logger file.
+For thread parallelism (e.g., with OpenMP), it is advised to put the
+logger call in a guarding region (e.g., in an OpenMP critical region).
 
 Note: Loggers of type `logger_type` normally report their messages to I/O
 units in the internal list termed `log_units`. However if `log_units`