http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47471
--- Comment #2 from Dodji Seketeli <dodji at gcc dot gnu.org> 2011-03-29
15:24:07 UTC ---
I believe the issue is that for that source code, GCC emits two
identical .loc asm directives for line 3. In theory I don't thing
doing that would be wrong.
But in practise the second .loc directive triggers a special opcode in
the generated line program that increments the line with an increment
of zero; it also increments the current program address with a
increment of zero. And that happens before the first line that
doesn't belong to the prologue.
That seems to break GDB's heuristic, and is also a bit of bloat.
The patch below avoids emitting two identical consecutive line number
debug information and seems to fix the issue for me. I am currently
regression-testing it.
>From eb1450a263a4e50b43132ef9b914f49a971c8e9d Mon Sep 17 00:00:00 2001
From: Dodji Seketeli <do...@redhat.com>
Date: Tue, 29 Mar 2011 16:56:20 +0200
Subject: [PATCH] PR debug/47471
gcc/
* dwarf2out.c (dwarf2out_source_line): Avoid emitting two
identical contiguous .loc asm directive.
gcc/testsuite/
* gcc.dg/debug/dwarf2/line-prog-1.c: New test.
---
gcc/dwarf2out.c | 33 +++++++++++++++-------
gcc/testsuite/gcc.dg/debug/dwarf2/line-prog-1.c | 25 +++++++++++++++++
2 files changed, 47 insertions(+), 11 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/debug/dwarf2/line-prog-1.c
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 7803ab7..b350f43 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -22068,6 +22068,8 @@ dwarf2out_source_line (unsigned int line, const char
*filename,
&& line != 0)
{
int file_num = maybe_emit_file (lookup_filename (filename));
+ static int prev_file_num;
+ static unsigned int prev_line;
switch_to_section (current_function_section ());
@@ -22078,19 +22080,28 @@ dwarf2out_source_line (unsigned int line, const char
*filename,
if (DWARF2_ASM_LINE_DEBUG_INFO)
{
- /* Emit the .loc directive understood by GNU as. */
- fprintf (asm_out_file, "\t.loc %d %d 0", file_num, line);
- if (is_stmt != last_is_stmt)
+ static int prev_file_num;
+ static unsigned int prev_line;
+ if (prev_file_num != file_num
+ || prev_line != line)
{
- fprintf (asm_out_file, " is_stmt %d", is_stmt ? 1 : 0);
- last_is_stmt = is_stmt;
- }
- if (SUPPORTS_DISCRIMINATOR && discriminator != 0)
- fprintf (asm_out_file, " discriminator %d", discriminator);
- fputc ('\n', asm_out_file);
+ /* Emit the .loc directive understood by GNU as. */
+ fprintf (asm_out_file, "\t.loc %d %d 0", file_num, line);
+ if (is_stmt != last_is_stmt)
+ {
+ fprintf (asm_out_file, " is_stmt %d", is_stmt ? 1 : 0);
+ last_is_stmt = is_stmt;
+ }
+ if (SUPPORTS_DISCRIMINATOR && discriminator != 0)
+ fprintf (asm_out_file, " discriminator %d", discriminator);
+ fputc ('\n', asm_out_file);
+
+ /* Indicate that line number info exists. */
+ line_info_table_in_use++;
- /* Indicate that line number info exists. */
- line_info_table_in_use++;
+ prev_file_num = file_num;
+ prev_line = line;
+ }
}
else if (function_section (current_function_decl) != text_section)
{
diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/line-prog-1.c
b/gcc/testsuite/gcc.dg/debug/dwarf2/line-prog-1.c
new file mode 100644
index 0000000..63637dc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/dwarf2/line-prog-1.c
@@ -0,0 +1,25 @@
+/*
+ Origin: PR debug/47471
+ { dg-options "-g -dA" }
+ */
+
+int v;
+void f (int i, ...)
+{
+ v++;
+}
+
+int
+main (void)
+{
+ f (1);
+ return 0;
+}
+
+/* We want to have only one .loc directive that points to the opening
+ curly bracket of the definition of function f, at line 8. */
+
+/*
+ { dg-final { scan-assembler-times "\.loc 1 8 0" 1 } }
+
+ */
--
1.7.3.4
