From 209fe0df24292a69ab4f34d10a5a8c417f64e2e9 Mon Sep 17 00:00:00 2001
From: Vadim Chugunov <vadimcn@gmail.com>
Date: Wed, 19 Oct 2016 00:25:03 -0700
Subject: [PATCH] Fix line stepping in debugger.

Attribute drop code to block's closing brace, instead of the line where the allocation was done.
Attribute function epilogues to function body's closing brace, rather than the function header.
---
 src/librustc_mir/build/mod.rs        |  5 +-
 src/librustc_mir/build/scope.rs      |  6 +-
 src/test/debuginfo/drop-locations.rs | 91 ++++++++++++++++++++++++++++
 3 files changed, 99 insertions(+), 3 deletions(-)
 create mode 100644 src/test/debuginfo/drop-locations.rs

diff --git a/src/librustc_mir/build/mod.rs b/src/librustc_mir/build/mod.rs
index 353aaaa45e18b..7b3306de7538b 100644
--- a/src/librustc_mir/build/mod.rs
+++ b/src/librustc_mir/build/mod.rs
@@ -176,8 +176,9 @@ pub fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
         unpack!(block = builder.in_scope(arg_extent, block, |builder| {
             builder.args_and_body(block, return_ty, &arguments, arg_extent, ast_block)
         }));
-
-        let source_info = builder.source_info(span);
+        // Attribute epilogue to function's closing brace
+        let fn_end = Span { lo: span.hi, ..span };
+        let source_info = builder.source_info(fn_end);
         let return_block = builder.return_block();
         builder.cfg.terminate(block, source_info,
                               TerminatorKind::Goto { target: return_block });
diff --git a/src/librustc_mir/build/scope.rs b/src/librustc_mir/build/scope.rs
index 01cce3c7dd794..ae6a1fb473b6d 100644
--- a/src/librustc_mir/build/scope.rs
+++ b/src/librustc_mir/build/scope.rs
@@ -521,8 +521,12 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 if let DropKind::Value { .. } = drop_kind {
                     scope.needs_cleanup = true;
                 }
+                let tcx = self.hir.tcx();
+                let extent_span = extent.span(&tcx.region_maps, &tcx.map).unwrap();
+                // Attribute scope exit drops to scope's closing brace
+                let scope_end = Span { lo: extent_span.hi, .. extent_span};
                 scope.drops.push(DropData {
-                    span: span,
+                    span: scope_end,
                     location: lvalue.clone(),
                     kind: drop_kind
                 });
diff --git a/src/test/debuginfo/drop-locations.rs b/src/test/debuginfo/drop-locations.rs
new file mode 100644
index 0000000000000..3a7c534c13902
--- /dev/null
+++ b/src/test/debuginfo/drop-locations.rs
@@ -0,0 +1,91 @@
+// Copyright 2013-2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-windows
+// ignore-android
+// min-lldb-version: 310
+
+#![allow(unused)]
+
+// compile-flags:-g
+
+// This test checks that drop glue code gets attributed to scope's closing brace,
+// and function epilogues - to function's closing brace.
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc1[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc2[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc3[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc4[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc5[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc6[...]
+
+// === LLDB TESTS ==================================================================================
+
+// lldb-command:set set stop-line-count-before 0
+// lldb-command:set set stop-line-count-after 1
+// Can't set both to zero or lldb will stop printing source at all.  So it will output the current
+// line and the next.  We deal with this by having at least 2 lines between the #loc's
+
+// lldb-command:run
+// lldb-command:next
+// lldb-command:frame select
+// lldb-check:[...]#loc1[...]
+// lldb-command:next
+// lldb-command:frame select
+// lldb-check:[...]#loc2[...]
+// lldb-command:next
+// lldb-command:frame select
+// lldb-check:[...]#loc3[...]
+// lldb-command:next
+// lldb-command:frame select
+// lldb-check:[...]#loc4[...]
+// lldb-command:next
+// lldb-command:frame select
+// lldb-check:[...]#loc5[...]
+// lldb-command:next
+// lldb-command:frame select
+// lldb-check:[...]#loc6[...]
+
+fn main() {
+
+    foo();
+
+    zzz(); // #loc5
+
+} // #loc6
+
+fn foo() {
+    {
+        let s = String::from("s"); // #break
+
+        zzz(); // #loc1
+
+    } // #loc2
+
+    zzz(); // #loc3
+
+} // #loc4
+
+fn zzz() {()}