[PING2] : [RFC/RFA] PING: skip __main

Pierre Muller
2008-05-30T11:19:05Z

Hi, is there any chance that someone will have
the time to review this patch?

Pierre Muller
Pascal language support maintainer for GDB

-----Message d'origine-----
De : gdb-patches-owner@sourceware.org
[mailto:gdb-patches-owner@sourceware.org] De la part de Pierre Muller
Envoyé : Friday, May 02, 2008 3:26 PM
À : 'Pedro Alves'; 'Daniel Jacobowitz'; gdb-patches@sourceware.org
Cc : 'Mark Kettenis'
Objet : [RFC/RFA] PING: skip __main

Pedro submitted this patch end of January,
but the 6.8 release pushed it to a later date.
http://sourceware.org/ml/gdb-patches/2008-01/msg00665.html

Now that GDB 6.8 is out,
I would really like to get this patch in.
Pedro, this is your work, but you seem to be
much more involved in other things lately,
thus, if you don't mind, I can try to push this through.

I updated the patch from the first message
referenced and just followed Daniel's advice in
http://sourceware.org/ml/gdb-patches/2008-01/msg00883.html
to change skip___main into skip_main_constructor.

This __main call seems to be
a common feature for coff format, thus
I suppose that it applies to other targets,
go32v2 djgpp is probably one of them.

For cygwin target, I get this:

=== gdb Summary ===

-# of expected passes 10733
-# of unexpected failures 560
+# of expected passes 10928
+# of unexpected failures 363
# of expected failures 59
# of unknown successes 2
-# of known failures 21
+# of known failures 23
# of unresolved testcases 40
# of untested testcases 14
# of unsupported tests 23

Almost 200 failures less...

Daniel wanted to get a comment from Mark
in his last email in that thread, that is the reason
why I added Mark Kettenis to the list of recipients.

Does this patch look OK now?

One point that should still be discussed is
if we should call main_name function
rather than hardcoded "main" in find_function_start_sal in symtab.c.

Pierre Muller
Pascal language support maintainer for GDB

2008-05-02 Pedro Alves <pedro_alves@portugalmail.pt>
Pierre Muller <muller@ics.u-strasbg.fr>

* gdbarch.sh (gdbarch_skip_main_constructor_call): New.
* gdbarch.h, gdbarch.c: Regenerate.

* i386-tdep.h (i386_skip_main_constructor_call): Declare.
* i386-tdep.c (i386_skip_main_constructor_call): New.
* i386-cygwin-tdep.c (i386_cygwin_init_abi): Register
i386_skip_main_constructor_call as
gdbarch_skip_main_constructor_call
gdbarch callback.
* symtab.c (find_function_start_sal): When pc points at the "main"
function, call gdbarch_skip_main_constructor_call.

Index: gdb/gdbarch.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.c,v
retrieving revision 1.422
diff -u -p -r1.422 gdbarch.c
--- gdb/gdbarch.c 22 Apr 2008 11:03:41 -0000 1.422
+++ gdb/gdbarch.c 30 Apr 2008 13:01:33 -0000
@@ -184,6 +184,7 @@ struct gdbarch
gdbarch_integer_to_address_ftype *integer_to_address;
gdbarch_return_value_ftype *return_value;
gdbarch_skip_prologue_ftype *skip_prologue;
+ gdbarch_skip_main_constructor_call_ftype *skip_main_constructor_call;
gdbarch_inner_than_ftype *inner_than;
gdbarch_breakpoint_from_pc_ftype *breakpoint_from_pc;
gdbarch_adjust_breakpoint_address_ftype *adjust_breakpoint_address;
@@ -306,6 +307,7 @@ struct gdbarch startup_gdbarch =
0, /* integer_to_address */
0, /* return_value */
0, /* skip_prologue */
+ 0, /* skip_main_constructor_call */
0, /* inner_than */
0, /* breakpoint_from_pc */
0, /* adjust_breakpoint_address */
@@ -542,6 +544,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
/* Skip verify of return_value, has predicate */
if (gdbarch->skip_prologue == 0)
fprintf_unfiltered (log, "\n\tskip_prologue");
+ /* Skip verify of skip_main_constructor_call, has predicate */
if (gdbarch->inner_than == 0)
fprintf_unfiltered (log, "\n\tinner_than");
if (gdbarch->breakpoint_from_pc == 0)
@@ -934,6 +937,12 @@ gdbarch_dump (struct gdbarch *gdbarch, s
"gdbarch_dump: single_step_through_delay =
<0x%lx>\n",
(long) gdbarch->single_step_through_delay);
fprintf_unfiltered (file,
+ "gdbarch_dump: gdbarch_skip_main_constructor_call_p()
= %d\n",
+ gdbarch_skip_main_constructor_call_p (gdbarch));
+ fprintf_unfiltered (file,
+ "gdbarch_dump: skip_main_constructor_call =
<0x%lx>\n",
+ (long) gdbarch->skip_main_constructor_call);
+ fprintf_unfiltered (file,
"gdbarch_dump: gdbarch_skip_permanent_breakpoint_p()
= %d\n",
gdbarch_skip_permanent_breakpoint_p (gdbarch));
fprintf_unfiltered (file,
@@ -2075,6 +2084,30 @@ set_gdbarch_skip_prologue (struct gdbarc
}

int
+gdbarch_skip_main_constructor_call_p (struct gdbarch *gdbarch)
+{
+ gdb_assert (gdbarch != NULL);
+ return gdbarch->skip_main_constructor_call != NULL;
+}
+
+CORE_ADDR
+gdbarch_skip_main_constructor_call (struct gdbarch *gdbarch, CORE_ADDR ip)
+{
+ gdb_assert (gdbarch != NULL);
+ gdb_assert (gdbarch->skip_main_constructor_call != NULL);
+ if (gdbarch_debug >= 2)
+ fprintf_unfiltered (gdb_stdlog, "gdbarch_skip_main_constructor_call
called\n");
+ return gdbarch->skip_main_constructor_call (gdbarch, ip);
+}
+
+void
+set_gdbarch_skip_main_constructor_call (struct gdbarch *gdbarch,
+ gdbarch_skip_main_constructor_call_ftype
skip_main_constructor_call)
+{
+ gdbarch->skip_main_constructor_call = skip_main_constructor_call;
+}
+
+int
gdbarch_inner_than (struct gdbarch *gdbarch, CORE_ADDR lhs, CORE_ADDR rhs)
{
gdb_assert (gdbarch != NULL);
Index: gdb/gdbarch.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.h,v
retrieving revision 1.377
diff -u -p -r1.377 gdbarch.h
--- gdb/gdbarch.h 29 Apr 2008 16:06:07 -0000 1.377
+++ gdb/gdbarch.h 30 Apr 2008 13:01:33 -0000
@@ -381,6 +381,12 @@ typedef CORE_ADDR (gdbarch_skip_prologue
extern CORE_ADDR gdbarch_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR
ip);
extern void set_gdbarch_skip_prologue (struct gdbarch *gdbarch,
gdbarch_skip_prologue_ftype *skip_prologue);

+extern int gdbarch_skip_main_constructor_call_p (struct gdbarch *gdbarch);
+
+typedef CORE_ADDR (gdbarch_skip_main_constructor_call_ftype) (struct
gdbarch *gdbarch, CORE_ADDR ip);
+extern CORE_ADDR gdbarch_skip_main_constructor_call (struct gdbarch
*gdbarch, CORE_ADDR ip);
+extern void set_gdbarch_skip_main_constructor_call (struct gdbarch
*gdbarch, gdbarch_skip_main_constructor_call_ftype
*skip_main_constructor_call);
+
typedef int (gdbarch_inner_than_ftype) (CORE_ADDR lhs, CORE_ADDR rhs);
extern int gdbarch_inner_than (struct gdbarch *gdbarch, CORE_ADDR lhs,
CORE_ADDR rhs);
extern void set_gdbarch_inner_than (struct gdbarch *gdbarch,
gdbarch_inner_than_ftype *inner_than);
Index: gdb/gdbarch.sh
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.sh,v
retrieving revision 1.463
diff -u -p -r1.463 gdbarch.sh
--- gdb/gdbarch.sh 29 Apr 2008 16:06:06 -0000 1.463
+++ gdb/gdbarch.sh 30 Apr 2008 13:01:34 -0000
@@ -483,6 +483,7 @@ M:CORE_ADDR:integer_to_address:struct ty
M:enum return_value_convention:return_value:struct type *functype, struct
type *valtype, struct regcache *regcache, gdb_byte *readbuf, const gdb_byte
*writebuf:functype, valtype, regcache, readbuf, writebuf

m:CORE_ADDR:skip_prologue:CORE_ADDR ip:ip:0:0
+M:CORE_ADDR:skip_main_constructor_call:CORE_ADDR ip:ip
f:int:inner_than:CORE_ADDR lhs, CORE_ADDR rhs:lhs, rhs:0:0
m:const gdb_byte *:breakpoint_from_pc:CORE_ADDR *pcptr, int *lenptr:pcptr,
lenptr::0:
M:CORE_ADDR:adjust_breakpoint_address:CORE_ADDR bpaddr:bpaddr
Index: gdb/i386-cygwin-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-cygwin-tdep.c,v
retrieving revision 1.16
diff -u -p -r1.16 i386-cygwin-tdep.c
--- gdb/i386-cygwin-tdep.c 1 Jan 2008 22:53:10 -0000 1.16
+++ gdb/i386-cygwin-tdep.c 30 Apr 2008 13:01:34 -0000
@@ -227,6 +227,8 @@ i386_cygwin_init_abi (struct gdbarch_inf

set_gdbarch_skip_trampoline_code (gdbarch,
i386_cygwin_skip_trampoline_code);

+ set_gdbarch_skip_main_constructor_call (gdbarch,
i386_skip_main_constructor_call);
+
tdep->struct_return = reg_struct_return;

tdep->gregset_reg_offset = i386_win32_gregset_reg_offset;
Index: gdb/i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.255
diff -u -p -r1.255 i386-tdep.c
--- gdb/i386-tdep.c 25 Apr 2008 14:57:30 -0000 1.255
+++ gdb/i386-tdep.c 30 Apr 2008 13:01:35 -0000
@@ -941,6 +941,33 @@ i386_skip_prologue (struct gdbarch *gdba
return pc;
}

+/* Check that the code pointed to by PC corresponds to a call to
+ __main, skip it if so. Return PC otherwise. */
+
+CORE_ADDR
+i386_skip_main_constructor_call (struct gdbarch *gdbarch, CORE_ADDR pc)
+{
+ gdb_byte op;
+
+ target_read_memory (pc, &op, 1);
+ if (op == 0xe8)
+ {
+ gdb_byte buf[4];
+ if (target_read_memory (pc + 1, buf, sizeof buf) == 0)
+ {
+ CORE_ADDR call_dest = pc + 5 + extract_unsigned_integer (buf, 4);
+
+ struct minimal_symbol *s = lookup_minimal_symbol_by_pc
(call_dest);
+ if (s != NULL
+ && SYMBOL_LINKAGE_NAME (s) != NULL
+ && strcmp (SYMBOL_LINKAGE_NAME (s), "__main") == 0)
+ pc += 5;
+ }
+ }
+
+ return pc;
+}
+
/* This function is 64-bit safe. */

static CORE_ADDR
Index: gdb/i386-tdep.h
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.h,v
retrieving revision 1.53
diff -u -p -r1.53 i386-tdep.h
--- gdb/i386-tdep.h 11 Mar 2008 05:21:38 -0000 1.53
+++ gdb/i386-tdep.h 30 Apr 2008 13:01:35 -0000
@@ -166,6 +166,7 @@ extern struct type *i386_sse_type (struc

/* Functions exported from i386-tdep.c. */
extern CORE_ADDR i386_pe_skip_trampoline_code (CORE_ADDR pc, char *name);
+extern CORE_ADDR i386_skip_main_constructor_call (struct gdbarch *gdbarch,
CORE_ADDR pc);

/* Return the name of register REGNUM. */
extern char const *i386_register_name (struct gdbarch * gdbarch, int
regnum);
Index: gdb/symtab.c
===================================================================
RCS file: /cvs/src/src/gdb/symtab.c,v
retrieving revision 1.177
diff -u -p -r1.177 symtab.c
--- gdb/symtab.c 19 Apr 2008 11:39:50 -0000 1.177
+++ gdb/symtab.c 30 Apr 2008 13:01:36 -0000
@@ -2572,6 +2572,21 @@ find_function_start_sal (struct symbol *
/* Recalculate the line number (might not be N+1). */
sal = find_pc_sect_line (pc, SYMBOL_BFD_SECTION (sym), 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 (funfirstline
+ && gdbarch_skip_main_constructor_call_p (current_gdbarch)
+ && SYMBOL_LINKAGE_NAME (sym)
+ && strcmp (SYMBOL_LINKAGE_NAME (sym), "main") == 0)
+ {
+ pc = gdbarch_skip_main_constructor_call (current_gdbarch, pc);
+ /* Recalculate the line number (might not be N+1). */
+ sal = find_pc_sect_line (pc, SYMBOL_BFD_SECTION (sym), 0);
+ }
+
sal.pc = pc;

return sal;