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ping: [rfc, 7.3?] -O2 -g breakpoints internal error + prologue skipping


Hi,

it would be sad if it misses 7.3, it has been post for (almost) two weeks now.

I do not think this patch is so clear to check it in on my own but I do not
see any regression-like flaws of it.


Thanks,
Jan


On Fri, 15 Apr 2011 22:16:37 +0200, Jan Kratochvil wrote:

obsoletes my:
	[patch] Fix internal error on some -O2 -g breakpoints
	http://sourceware.org/ml/gdb-patches/2010-07/msg00533.html
and IMO also Paul's:
	[patch] Fix for PR gdb/12573
	http://sourceware.org/ml/gdb-patches/2011-03/msg00883.html
it is an improvement of:
	[patch] Do not skip prologue for -O2 -g with GCC VTA Re: [patch] Fix for PR gdb/12573
	http://sourceware.org/ml/gdb-patches/2011-03/msg01129.html

Just the removal of gdb_assert may place the breakpoints on -O2 -g code too
late.  IMO on `(gdb) break Bar::Bar' no real inferior modification should
happen while with the Paul's reproducer in the PR the `free(malloc(1));' line
is already executed when GDB stops.  This over-execution is tested in the
attached artificial reproducer by the testcase "no statement got executed".

There are several issues of this patch:

#1 The two-pass complicated execution in skip_prologue_sal currently has no
effect as the functionality depending on it does not work now.  But that is
a separate new Bug and the two passes will be needed after its fix:
	regression by physname: PE32 prologue skip vs. static initializers
	http://sourceware.org/bugzilla/show_bug.cgi?id=12680

#2 A conservative approach has been taken.  The problematic prologue skipping
is disabled only if .debug_loc reference is found which proves -O2 (with -g).
     This test is imperfect as there may exist optimized debug code not using 
     any location list and still facing inlining issues if handled as
     unoptimized code.  For a future better test see GCC PR other/32998.
     GCC PR other/32998 = -frecord-gcc-switches issues, Status: NEW
The opposite option would be to keep the prologue skipping enabled only if
there is any DW_AT_location(DW_OP_fbreg(x)).  I haven't tested this way, it
seems very intrusive to me.  In practice I doubt there will be a real world
case of -O2 -g CU not referencing .debug_loc - such as if all its code accesses
only global variables and has no local variables.  Just the testcase originally
was such a countercase CU. :-/  The GDB internal error is kept in place as it
still can happen in such case, this problem is not yet fully fixed.

#3 Whether a .debug_loc reference may be present with still invalid
DW_AT_location before prologue I do not know, it does not seem to happen for
GCC.  There is currently no DW_AT_producer check.  Even before VTA (Variable
Tracking Assignments, since FSF GCC 4.5, -O2 -g variables DW_AT_location
improvement) it seems to me the validity at function entry point worked well
enough.

#4 This whole problems appears only with involvement of inlined code, either
explicitly or implicitly.  But GDB does not support inlined code breakpoints
well (PR breakpoints/10738, RH BZ#149125).  When one plays with testing this
patch various suitable breakpoints are not placed but AFAIK all of them are in
the scope of the PR 10738.

#5 If function does not start is not on a line boundary the multi-location
breakpoints are already not found properly and everything fails.  I do not
think it can ever happen in real world.  Even for a singe-line code
    void f (void) {} void g (void) {}
GCC places there multiple line markers - -O2 -g, duplicity is for prologues:
File name                            Line number    Starting address
1.c                                            1                   0
1.c                                            1                   0
1.c                                            1                0x10
1.c                                            1                0x10


Whether this should go for 7.3 I am not sure.  The simple removal of
gdb_assert looks nice, GDB does not crash. But GDB behaves wrong and `break
func' may not stop before a crash there at all etc.

No regressions on {x86_64,x86_64-m32,i686}-fedora15-linux-gnu.

I will to commit it without any review/discussion.


Thanks,
Jan


gdb/
2011-04-15  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* dwarf2read.c (struct dwarf2_cu): New field has_loclist.
	(process_full_comp_unit): Set also symtab->locations_valid.  Move the
	symtab->language code.
	(var_decode_location): Set cu->has_loclist.
	* symtab.c (skip_prologue_sal): New variables saved_pc, force_skip and
	skip.  Intialize force_skip from locations_valid.  Move the prologue
	skipping code into two passes.
	* symtab.h (struct symtab): Make the primary field a bitfield.  New
	field locations_valid.

gdb/testsuite/
2011-04-15  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.dwarf2/dw2-skip-prologue.S: New file.
	* gdb.dwarf2/dw2-skip-prologue.c: New file.
	* gdb.dwarf2/dw2-skip-prologue.exp: New file.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -396,6 +396,13 @@ struct dwarf2_cu
      DIEs for namespaces, we don't need to try to infer them
      from mangled names.  */
   unsigned int has_namespace_info : 1;
+
+  /* This CU references .debug_loc.  See the symtab->locations_valid field.
+     This test is imperfect as there may exist optimized debug code not using
+     any location list and still facing inlining issues if handled as
+     unoptimized code.  For a future better test see GCC PR other/32998.  */
+
+  unsigned int has_loclist : 1;
 };
 
 /* Persistent data held for a compilation unit, even when not
@@ -4654,13 +4661,15 @@ process_full_comp_unit (struct dwarf2_per_cu_data *per_cu)
 
   symtab = end_symtab (highpc + baseaddr, objfile, SECT_OFF_TEXT (objfile));
 
-  /* Set symtab language to language from DW_AT_language.
-     If the compilation is from a C file generated by language preprocessors,
-     do not set the language if it was already deduced by start_subfile.  */
-  if (symtab != NULL
-      && !(cu->language == language_c && symtab->language != language_c))
+  if (symtab != NULL)
     {
-      symtab->language = cu->language;
+      /* Set symtab language to language from DW_AT_language.  If the
+	 compilation is from a C file generated by language preprocessors, do
+	 not set the language if it was already deduced by start_subfile.  */
+      if (!(cu->language == language_c && symtab->language != language_c))
+	symtab->language = cu->language;
+
+      symtab->locations_valid = cu->has_loclist;
     }
 
   if (dwarf2_per_objfile->using_index)
@@ -10959,6 +10968,9 @@ var_decode_location (struct attribute *attr, struct symbol *sym,
 
   dwarf2_symbol_mark_computed (attr, sym, cu);
   SYMBOL_CLASS (sym) = LOC_COMPUTED;
+
+  if (SYMBOL_COMPUTED_OPS (sym) == &dwarf2_loclist_funcs)
+    cu->has_loclist = 1;
 }
 
 /* Given a pointer to a DWARF information entry, figure out if we need
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -2454,12 +2454,13 @@ skip_prologue_sal (struct symtab_and_line *sal)
   struct symbol *sym;
   struct symtab_and_line start_sal;
   struct cleanup *old_chain;
-  CORE_ADDR pc;
+  CORE_ADDR pc, saved_pc;
   struct obj_section *section;
   const char *name;
   struct objfile *objfile;
   struct gdbarch *gdbarch;
   struct block *b, *function_block;
+  int force_skip, skip;
 
   /* Do not change the SAL is PC was specified explicitly.  */
   if (sal->explicit_pc)
@@ -2497,46 +2498,69 @@ skip_prologue_sal (struct symtab_and_line *sal)
 
   gdbarch = get_objfile_arch (objfile);
 
-  /* If the function is in an unmapped overlay, use its unmapped LMA address,
-     so that gdbarch_skip_prologue has something unique to work on.  */
-  if (section_is_overlay (section) && !section_is_mapped (section))
-    pc = overlay_unmapped_address (pc, section);
+  /* Process the prologue in two passes.  In the first pass try to skip the
+     prologue (SKIP is true) and verify there is a real need for it (indicated
+     by FORCE_SKIP).  If no such reason was found run a second pass where the
+     prologue is not skipped (SKIP is false).  */
 
-  /* Skip "first line" of function (which is actually its prologue).  */
-  pc += gdbarch_deprecated_function_start_offset (gdbarch);
-  pc = gdbarch_skip_prologue (gdbarch, pc);
+  skip = 1;
+  force_skip = 1;
 
-  /* For overlays, map pc back into its mapped VMA range.  */
-  pc = overlay_mapped_address (pc, section);
+  /* Be conservative - allow direct PC (without skipping prologue) only if we
+     have proven the CU (Compilation Unit) supports it.  sal->SYMTAB does not
+     have to be set by the caller so we use SYM instead.  */
+  if (sym && SYMBOL_SYMTAB (sym)->locations_valid)
+    force_skip = 0;
 
-  /* Calculate line number.  */
-  start_sal = find_pc_sect_line (pc, section, 0);
-
-  /* Check if gdbarch_skip_prologue left us in mid-line, and the next
-     line is still part of the same function.  */
-  if (start_sal.pc != pc
-      && (sym? (BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) <= start_sal.end
-	        && start_sal.end < BLOCK_END (SYMBOL_BLOCK_VALUE (sym)))
-          : (lookup_minimal_symbol_by_pc_section (start_sal.end, section)
-             == lookup_minimal_symbol_by_pc_section (pc, section))))
+  saved_pc = pc;
+  do
     {
-      /* First pc of next line */
-      pc = start_sal.end;
-      /* Recalculate the line number (might not be N+1).  */
-      start_sal = find_pc_sect_line (pc, section, 0);
-    }
+      pc = saved_pc;
 
-  /* On targets with executable formats that don't have a concept of
-     constructors (ELF with .init has, PE doesn't), gcc emits a call
-     to `__main' in `main' between the prologue and before user
-     code.  */
-  if (gdbarch_skip_main_prologue_p (gdbarch)
-      && name && strcmp (name, "main") == 0)
-    {
-      pc = gdbarch_skip_main_prologue (gdbarch, pc);
-      /* Recalculate the line number (might not be N+1).  */
+      /* If the function is in an unmapped overlay, use its unmapped LMA address,
+	 so that gdbarch_skip_prologue has something unique to work on.  */
+      if (section_is_overlay (section) && !section_is_mapped (section))
+	pc = overlay_unmapped_address (pc, section);
+
+      /* Skip "first line" of function (which is actually its prologue).  */
+      pc += gdbarch_deprecated_function_start_offset (gdbarch);
+      if (skip)
+	pc = gdbarch_skip_prologue (gdbarch, pc);
+
+      /* For overlays, map pc back into its mapped VMA range.  */
+      pc = overlay_mapped_address (pc, section);
+
+      /* Calculate line number.  */
       start_sal = find_pc_sect_line (pc, section, 0);
+
+      /* Check if gdbarch_skip_prologue left us in mid-line, and the next
+	 line is still part of the same function.  */
+      if (skip && start_sal.pc != pc
+	  && (sym? (BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) <= start_sal.end
+		    && start_sal.end < BLOCK_END (SYMBOL_BLOCK_VALUE (sym)))
+	      : (lookup_minimal_symbol_by_pc_section (start_sal.end, section)
+		 == lookup_minimal_symbol_by_pc_section (pc, section))))
+	{
+	  /* First pc of next line */
+	  pc = start_sal.end;
+	  /* Recalculate the line number (might not be N+1).  */
+	  start_sal = find_pc_sect_line (pc, section, 0);
+	}
+
+      /* On targets with executable formats that don't have a concept of
+	 constructors (ELF with .init has, PE doesn't), gcc emits a call
+	 to `__main' in `main' between the prologue and before user
+	 code.  */
+      if (gdbarch_skip_main_prologue_p (gdbarch)
+	  && name && strcmp (name, "main") == 0)
+	{
+	  pc = gdbarch_skip_main_prologue (gdbarch, pc);
+	  /* Recalculate the line number (might not be N+1).  */
+	  start_sal = find_pc_sect_line (pc, section, 0);
+	  force_skip = 1;
+	}
     }
+  while (!force_skip && skip--);
 
   /* If we still don't have a valid source line, try to find the first
      PC in the lineinfo table that belongs to the same function.  This
@@ -2546,7 +2570,7 @@ skip_prologue_sal (struct symtab_and_line *sal)
      the case with the DJGPP target using "gcc -gcoff" when the
      compiler inserted code after the prologue to make sure the stack
      is aligned.  */
-  if (sym && start_sal.symtab == NULL)
+  if (!force_skip && sym && start_sal.symtab == NULL)
     {
       pc = skip_prologue_using_lineinfo (pc, SYMBOL_SYMTAB (sym));
       /* Recalculate the line number.  */
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -767,7 +767,13 @@ struct symtab
      should be designated the primary, so that the blockvector
      is relocated exactly once by objfile_relocate.  */
 
-  int primary;
+  unsigned int primary : 1;
+
+  /* Symtab has been compiled with both optimizations and debug info so that
+     GDB may stop skipping prologues as variables locations are valid already
+     at function entry points.  */
+
+  unsigned int locations_valid : 1;
 
   /* The macro table for this symtab.  Like the blockvector, this
      may be shared between different symtabs --- and normally is for
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-skip-prologue.S
@@ -0,0 +1,391 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	func_start			/* DW_AT_low_pc */
+	.4byte	func_end			/* DW_AT_high_pc */
+	.ascii	"main.c\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	2				/* DW_AT_language (DW_LANG_C) */
+
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.ascii		"func\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		func_start		/* DW_AT_low_pc */
+	.4byte		func_end		/* DW_AT_high_pc */
+
+/* GDB `has_loclist' detection of -O2 -g code needs to see a DW_AT_location
+   location list.  There may exist -O2 -g CUs still not needing/using any such
+   location list - exactly like this CU.  Make one up.  */
+
+	.uleb128	0x7			/* (DIE (0x42) DW_TAG_formal_parameter) */
+	.ascii		"param\0"		/* DW_AT_name */
+	.long		.Ltype_int - .Lcu1_begin	/* DW_AT_type */
+	.long		loclist			/* DW_AT_location */
+
+	.uleb128	4			/* Abbrev: DW_TAG_inlined_subroutine */
+	.ascii		"inlined\0"		/* DW_AT_name */
+	.4byte		func0			/* DW_AT_low_pc */
+	.4byte		func1			/* DW_AT_high_pc */
+	.byte		3			/* DW_AT_inline (DW_INL_declared_inlined) */
+	.byte		1			/* DW_AT_call_file */
+	.byte		8			/* DW_AT_call_line */
+
+	.uleb128	4			/* Abbrev: DW_TAG_inlined_subroutine */
+	.ascii		"inlined2\0"		/* DW_AT_name */
+	.4byte		func2			/* DW_AT_low_pc */
+	.4byte		func3			/* DW_AT_high_pc */
+	.byte		3			/* DW_AT_inline (DW_INL_declared_inlined) */
+	.byte		1			/* DW_AT_call_file */
+	.byte		11			/* DW_AT_call_line */
+
+#ifdef INLINED
+	.uleb128	4			/* Abbrev: DW_TAG_inlined_subroutine */
+	.ascii		"otherinline\0"		/* DW_AT_name */
+	.4byte		func3			/* DW_AT_low_pc */
+	.4byte		func_end		/* DW_AT_high_pc */
+	.byte		3			/* DW_AT_inline (DW_INL_declared_inlined) */
+	.byte		1			/* DW_AT_call_file */
+	.byte		9			/* DW_AT_call_line */
+#endif
+
+#ifdef LEXICAL
+	.uleb128	5			/* Abbrev: DW_TAG_lexical_block */
+	.4byte		func3			/* DW_AT_low_pc */
+	.4byte		func_end		/* DW_AT_high_pc */
+
+	/* GDB would otherwise ignore the DW_TAG_lexical_block.  */
+	.uleb128	6			/* Abbrev: DW_TAG_variable */
+	.ascii		"lexicalvar\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+
+	.byte		0			/* End of children of DW_TAG_lexical_block */
+#endif
+
+	.byte		0			/* End of children of DW_TAG_subprogram */
+
+/* Simulate `fund' is also named `func' so that the function name matches and
+   fund's SAL is not discarded in expand_line_sal_maybe.  */
+
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.ascii		"func\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		fund_start		/* DW_AT_low_pc */
+	.4byte		fund_end		/* DW_AT_high_pc */
+
+	.byte		0			/* End of children of DW_TAG_subprogram */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+	.section	.debug_loc
+loclist:
+	/* Reset the location list base address first.  */
+	.long		-1, 0
+
+	.long		func_start, func_end
+	.2byte		2f-1f
+1:	.byte		0x50	/* DW_OP_reg0 */
+2:
+	/* Location list end.  */
+	.long	0, 0
+
+/* Abbrev table */
+	.section .debug_abbrev
+.Labbrev1_begin:
+	.uleb128	1			/* Abbrev code */
+	.uleb128	0x11			/* DW_TAG_compile_unit */
+	.byte		1			/* has_children */
+	.uleb128	0x10			/* DW_AT_stmt_list */
+	.uleb128	0x6			/* DW_FORM_data4 */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x25			/* DW_AT_producer */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x13			/* DW_AT_language */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	2			/* Abbrev code */
+	.uleb128	0x2e			/* DW_TAG_subprogram */
+	.byte		1			/* has_children */
+	.uleb128	0x3f			/* DW_AT_external */
+	.uleb128	0xc			/* DW_FORM_flag */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	3			/* Abbrev code */
+	.uleb128	0x24			/* DW_TAG_base_type */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0xb			/* DW_AT_byte_size */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x3e			/* DW_AT_encoding */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	4			/* Abbrev code */
+	.uleb128	0x1d			/* DW_TAG_inlined_subroutine */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x20			/* DW_AT_inline */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x58			/* DW_AT_call_file */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x59			/* DW_AT_call_line */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	5			/* Abbrev code */
+	.uleb128	0x0b			/* DW_TAG_lexical_block */
+	.byte		1			/* has_children */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	6			/* Abbrev code */
+	.uleb128	0x34			/* DW_TAG_variable */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	0x7			/* (abbrev code) */
+	.uleb128	0x5			/* (TAG: DW_TAG_formal_parameter) */
+	.byte		0x0			/* DW_children_no */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* (DW_AT_type) */
+	.uleb128	0x13			/* (DW_FORM_ref4) */
+	.uleb128	0x02			/* (DW_AT_location) */
+	.uleb128	0x06			/* (DW_FORM_data4) */
+	.byte		0x0
+	.byte		0x0
+
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"main.c\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.ascii		"other.c\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		func_start
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	4	/* ... to 5 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		func0
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	2
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	-4	/* ... to 1 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		func1
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	1
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	8	/* ... to 9 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		func2
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	2
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	-8	/* ... to 1 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		func3
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	1
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	8	/* ... to 9 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		func_end
+
+/* Equivalent copy but renamed s/func/fund/.  */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		fund_start
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	-4	/* ... to 5 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		fund0
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	2
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	-4	/* ... to 1 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		fund1
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	1
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	8	/* ... to 9 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		fund2
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	2
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	-8	/* ... to 1 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		fund3
+	.byte		4	/* DW_LNS_set_file */
+	.uleb128	1
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	8	/* ... to 9 */
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		fund_end
+
+/* Line numbering end.  */
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-skip-prologue.c
@@ -0,0 +1,58 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+static volatile int v;
+
+asm ("func_start: .globl func_start\n");
+static int
+func (void)
+{
+  v++;
+asm ("func0: .globl func0\n");
+  v++;
+asm ("func1: .globl func1\n");
+  v++;
+asm ("func2: .globl func2\n");
+  v++;
+asm ("func3: .globl func3\n");
+  return v;
+}
+asm ("func_end: .globl func_end\n");
+
+/* Equivalent copy but renamed s/func/fund/.  */
+
+asm ("fund_start: .globl fund_start\n");
+static int
+fund (void)
+{
+  v++;
+asm ("fund0: .globl fund0\n");
+  v++;
+asm ("fund1: .globl fund1\n");
+  v++;
+asm ("fund2: .globl fund2\n");
+  v++;
+asm ("fund3: .globl fund3\n");
+  return v;
+}
+asm ("fund_end: .globl fund_end\n");
+
+int
+main (void)
+{
+  return func () + fund ();
+}
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-skip-prologue.exp
@@ -0,0 +1,74 @@
+# Copyright 2011 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+load_lib dwarf.exp
+
+# Test multiple location breakpoints vs. prologue analysis on -O2 -g code.
+# when the first statement of a function is an inlined function GDB could
+# crash.  Map of this testcase:
+# 
+# File name                            Line number    Starting address
+# main.c                                         5    func_start
+# other.c                                        1    func0
+# 	`inlined' called at main.c line 8
+# main.c                                         9    func1
+# 	func1 = Breakpoint location 1
+# other.c                                        1    func2
+# 	`inlined2' called at main.c line 11
+# main.c                                         9    func3
+# 	func3 = Breakpoint location 2
+# 	`otherinline' called at main.c line 9
+# end of main                                         func_end
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0  
+}
+
+set testfile "dw2-skip-prologue"
+set executable ${testfile}
+set binfile ${objdir}/${subdir}/${executable}
+
+if {[build_executable ${testfile}.exp ${executable} "${testfile}.c ${testfile}.S" {additional_flags=-DINLINED}] == -1} {
+    return -1
+}
+
+# We need those symbols global to access them from the .S file.
+set test "strip stub symbols"
+set objcopy_program [transform objcopy]
+set result [catch "exec $objcopy_program							\
+			-N func0 -N func1 -N func2 -N func3         -N func_start -N func_end	\
+			-N fund0 -N fund1 -N fund2 -N fund3 -N fund -N fund_start		\
+			${binfile}" output]
+verbose "result is $result"
+verbose "output is $output"
+if {$result != 0} {
+    fail $test
+    return
+}
+pass $test
+
+clean_restart $executable
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_breakpoint "func"
+gdb_continue_to_breakpoint "func"
+
+# Sanity check GDB has really found 2 locations
+gdb_test {info break $bpnum} "\r\n2\\.1\[ \t\]\[^\n\]*\r\n2\\.2\[ \t\]\[^\n\]*" "2 locations found"
+
+gdb_test "p v" " = 0" "no statement got executed"


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