Add GDB pretty-printers for zend_ast, zval (#13520)

Author: arnaud-lb

.gdb.py

@@ -5,9 +5,15 @@
 
     source .gdb.py
 
-Use
+If needed, pretty printers can be by-passed by using the /r flag:
   (gdb) p /r any_variable
-to print |any_variable| without using any printers.
+
+Use |set print pretty| to enable multi-line printing and indentation:
+  (gdb) set print pretty on
+
+Use |set print max-depth| to control the maximum print depth for nested
+structures:
+  (gdb) set print pretty on
 
 To interactively type Python for development of the printers, use
   (gdb) python foo = gdb.parse_and_eval('bar')
@@ -32,7 +38,10 @@ def to_string(self):
 
     def children(self):
         for field in self.val.type.fields():
-            yield (field.name, self.val[field.name])
+            if field.name == 'val':
+                yield ('val', self.format_string())
+            else:
+                yield (field.name, self.val[field.name])
 
     def format_string(self):
         len = int(self.val['len'])
@@ -49,14 +58,16 @@ def format_string(self):
             str += ' (%d bytes total)' % int(self.val['len'])
 
         return str
+
+
 pp_set.add_printer('zend_string', '^_zend_string$', ZendStringPrettyPrinter)
 
 class ZendTypePrettyPrinter(gdb.printing.PrettyPrinter):
     "Print a zend_type"
 
     def __init__(self, val):
         self.val = val
-        self.load_bits()
+        load_type_bits()
 
     def to_string(self):
         return self.format_type(self.val)
@@ -73,7 +84,7 @@ def format_type(self, t):
         meta = []
         for bit in range(0, type_mask_size):
             if type_mask & (1 << bit):
-                type_name = self.bits.get(bit)
+                type_name = type_bit_to_name.get(bit)
                 match type_name:
                     case None:
                         parts.append('(1<<%d)' % bit)
@@ -104,34 +115,225 @@ def format_type(self, t):
 
         return str
 
-    def load_bits(self):
-        (symbol,_) = gdb.lookup_symbol("zend_gc_refcount")
-        if symbol == None:
-            raise "Could not find zend_types.h: symbol zend_gc_refcount not found"
-        filename = symbol.symtab.fullname()
 
-        bits = {}
+pp_set.add_printer('zend_type', '^zend_type$', ZendTypePrettyPrinter)
+
+class ZendAstKindPrettyPrinter(gdb.printing.PrettyPrinter):
+    "Print a zend_ast_kind"
+
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val.cast(gdb.lookup_type('enum _zend_ast_kind'))
+
+
+pp_set.add_printer('zend_ast_kind', '^zend_ast_kind$', ZendAstKindPrettyPrinter)
+
+class ZendAstPrettyPrinter(gdb.printing.PrettyPrinter):
+    "Print a zend_ast"
+
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return '((%s*)0x%x)' % (str(self.cast().type), self.val.address)
+
+    def children(self):
+        val = self.cast()
+        for field in val.type.fields():
+            if field.name == 'child':
+                children = val[field.name]
+                num_children = self.num_children()
+
+                ptr_type = gdb.lookup_type('zend_ast').pointer().pointer()
+                children = children.cast(ptr_type)
+
+                for i in range(0, num_children):
+                    c = children[i]
+                    if int(c) != 0:
+                        c = c.dereference()
+                    yield ('child[%d]' % i, c)
+            elif field.name == 'name':
+                yield (field.name, ZendStringPrettyPrinter(val[field.name].dereference()).to_string())
+            elif field.name == 'val':
+                yield (field.name, ZvalPrettyPrinter(val[field.name]).to_string())
+            else:
+                yield (field.name, val[field.name])
+
+    def is_special(self):
+        special_shift = 6 # ZEND_AST_SPECIAL_SHIFT
+        kind = self.val['kind']
+        return (kind >> special_shift) & 1
+
+    def is_decl(self):
+        return self.is_special() and int(self.val['kind']) >= enum_value('ZEND_AST_FUNC_DECL')
+
+    def is_list(self):
+        list_shift = 7 # ZEND_AST_IS_LIST_SHIFT
+        kind = self.val['kind']
+        return (kind >> list_shift) & 1
 
-        with open(filename, 'r') as file:
-            content = file.read()
+    def cast(self):
+        kind = int(self.val['kind'])
 
-            pattern = re.compile(r'#define _ZEND_TYPE_([^\s]+)_BIT\s+\(1u << (\d+)\)')
-            matches = pattern.findall(content)
-            for name, bit in matches:
+        if kind == enum_value('ZEND_AST_ZVAL') or kind == enum_value('ZEND_AST_CONSTANT'):
+            return self.val.cast(gdb.lookup_type('zend_ast_zval'))
+        if kind == enum_value('ZEND_AST_ZNODE'):
+            return self.val.cast(gdb.lookup_type('zend_ast_znode'))
+        if self.is_decl():
+            return self.val.cast(gdb.lookup_type('zend_ast_decl'))
+        if self.is_list():
+            return self.val.cast(gdb.lookup_type('zend_ast_list'))
+
+        return self.val
+
+    def num_children(self):
+        if self.is_decl():
+            decl_type = gdb.lookup_type('zend_ast_decl')
+            child_type = decl_type['child'].type
+            return array_size(child_type)
+        if self.is_special():
+            return 0
+        elif self.is_list():
+            return int(self.cast()['children'])
+        else:
+            num_children_shift = 8 # ZEND_AST_NUM_CHILDREN_SHIFT
+            kind = self.val['kind']
+            return kind >> num_children_shift
+
+
+pp_set.add_printer('zend_ast', '^_zend_ast$', ZendAstPrettyPrinter)
+
+class ZvalPrettyPrinter(gdb.printing.PrettyPrinter):
+    "Print a zval"
+
+    def __init__(self, val):
+        self.val = val
+        load_type_bits()
+
+    def to_string(self):
+        return self.value_to_string()
+
+    def value_to_string(self):
+        t = int(self.val['u1']['v']['type'])
+        if t == type_name_to_bit['undef']:
+            return 'undef'
+        elif t == type_name_to_bit['null']:
+            return 'null'
+        elif t == type_name_to_bit['false']:
+            return 'false'
+        elif t == type_name_to_bit['true']:
+            return 'true'
+        elif t == type_name_to_bit['long']:
+            return str(self.val['value']['lval'])
+        elif t == type_name_to_bit['double']:
+            return str(self.val['value']['dval'])
+        elif t == type_name_to_bit['string']:
+            return ZendStringPrettyPrinter(self.val['value']['str'].dereference()).to_string()
+        elif t == type_name_to_bit['array']:
+            return 'array'
+        elif t == type_name_to_bit['object']:
+            return 'object(%s)' % ZendStringPrettyPrinter(self.val['value']['obj']['ce']['name'].dereference()).to_string()
+        elif t == type_name_to_bit['resource']:
+            return 'resource'
+        elif t == type_name_to_bit['reference']:
+            return 'reference'
+        elif t == type_name_to_bit['constant_ast']:
+            return 'constant_ast'
+        else:
+            return 'zval of type %d' % int(self.val['u1']['v']['type'])
+
+    def children(self):
+        for field in self.val.type.fields():
+            if field.name == 'value':
+                value = self.val['value']
+                t = int(self.val['u1']['v']['type'])
+                if t == type_name_to_bit['undef']:
+                    value = value['lval']
+                elif t == type_name_to_bit['null']:
+                    value = value['lval']
+                elif t == type_name_to_bit['false']:
+                    value = value['lval']
+                elif t == type_name_to_bit['true']:
+                    value = value['lval']
+                elif t == type_name_to_bit['long']:
+                    value = value['lval']
+                elif t == type_name_to_bit['double']:
+                    value = value['dval']
+                elif t == type_name_to_bit['string']:
+                    value = value['str'].dereference()
+                elif t == type_name_to_bit['array']:
+                    value = value['ht'].dereference()
+                elif t == type_name_to_bit['object']:
+                    value = value['obj'].dereference()
+                elif t == type_name_to_bit['resource']:
+                    value = value['res'].dereference()
+                elif t == type_name_to_bit['reference']:
+                    value = value['ref'].dereference()
+                elif t == type_name_to_bit['constant_ast']:
+                    value = value['ast'].dereference()
+                else:
+                    value = value['ptr']
+                yield (field.name, value)
+            elif field.name == 'u2':
+                yield ('u2', self.val[field.name]['extra'])
+            else:
+                yield (field.name, self.val[field.name])
+
+
+pp_set.add_printer('zval', '^_zval_struct$', ZvalPrettyPrinter)
+
+type_bit_to_name = None
+type_name_to_bit = None
+
+def load_type_bits():
+    global type_bit_to_name
+    global type_name_to_bit
+
+    if type_bit_to_name != None:
+        return
+
+    (symbol,_) = gdb.lookup_symbol("zend_gc_refcount")
+    if symbol == None:
+        raise "Could not find zend_types.h: symbol zend_gc_refcount not found"
+    filename = symbol.symtab.fullname()
+
+    bits = {}
+
+    with open(filename, 'r') as file:
+        content = file.read()
+
+        pattern = re.compile(r'#define _ZEND_TYPE_([^\s]+)_BIT\s+\(1u << (\d+)\)')
+        matches = pattern.findall(content)
+        for name, bit in matches:
+            bits[int(bit)] = name.lower()
+
+        pattern = re.compile(r'#define IS_([^\s]+)\s+(\d+)')
+        matches = pattern.findall(content)
+        for name, bit in matches:
+            if not int(bit) in bits:
                 bits[int(bit)] = name.lower()
 
-            pattern = re.compile(r'#define IS_([^\s]+)\s+(\d+)')
-            matches = pattern.findall(content)
-            for name, bit in matches:
-                if not int(bit) in bits:
-                    bits[int(bit)] = name.lower()
+    types = {}
+    for bit in bits:
+        types[bits[bit]] = bit
 
-        types = {}
-        for bit in bits:
-            types[bits[bit]] = bit
+    type_bit_to_name = bits
+    type_name_to_bit = types
 
-        self.bits = bits
-        self.types = types
-pp_set.add_printer('zend_type', '^zend_type$', ZendTypePrettyPrinter)
+def lookup_symbol(name):
+    (symbol, _) = gdb.lookup_symbol(name)
+    if symbol == None:
+        raise Exception("Could not lookup symbol %s" % name)
+    return symbol
+
+def enum_value(name):
+    symbol = lookup_symbol(name)
+    return int(symbol.value())
+
+def array_size(ary_type):
+    # array types have a single field whose type represents its range
+    return ary_type.fields()[0].type.range()[1]+1
 
 gdb.printing.register_pretty_printer(gdb, pp_set, replace=True)