Re: [RFA] Pb stepping inside DLL function

Joel Brobecker
2004-06-24T00:23:07Z

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[Sigh... With the patch, this time...]

Hello,

We have the following little C program (a.c):

#include <stdio.h>

extern _stdcall int sub ();

main ()
{
int a = 0;

a = sub ();
printf ("%d\n", a);
}

``sub()'' is a function provided by a DLL. It has all the necessary
debug information. The following transcript shows that GDB is currently
unable to step into sub():

(gdb) start
Breakpoint 1 at 0x4012d2: file a.c, line 7.
Starting program: /[...]/a.exe
main () at a.c:7
7 int a = 0;
(gdb) step
9 a = sub ();
(gdb) p a
$1 = 0
(gdb) step
10 printf ("%d\n", a);
(gdb) print a
$2 = 5

During the step, GDB lands inside sub@0, which is the trampoline
for sub(), but doesn't realize it. The fix is to teach GDB how to
recognize them, and hand to find where they will eventually take us.
For that, I found a function that was actually dead but did exactly
what I needed, so I reused it.

2004-06-23 Joel Brobecker <brobecker@gnat.com>

* i386-cygwin-tdep.c (i386-cygwin-tdep.c): New function.
(i386_cygwin_in_solib_call_trampoline): New function.
(i386_cygwin_init_abi): Initialize the in_solib_call_trampoline
and skip_trampoline_code gdbarch methods.

Tested on x86-windows (XP), no regression.
OK to apply?

Thanks,
--
Joel

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Index: i386-cygwin-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-cygwin-tdep.c,v
retrieving revision 1.5
diff -u -p -r1.5 i386-cygwin-tdep.c
--- i386-cygwin-tdep.c 30 Apr 2004 21:13:58 -0000 1.5
+++ i386-cygwin-tdep.c 24 Jun 2004 00:12:25 -0000
@@ -26,11 +26,27 @@

#include "i386-tdep.h"

+static CORE_ADDR
+i386_cygwin_skip_trampoline_code (CORE_ADDR pc)
+{
+ return i386_pe_skip_trampoline_code (pc, NULL);
+}
+
+static int
+i386_cygwin_in_solib_call_trampoline (CORE_ADDR pc, char *name)
+{
+ return (i386_pe_skip_trampoline_code (pc, name) != 0);
+}
+
static void
i386_cygwin_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

+ set_gdbarch_in_solib_call_trampoline (gdbarch,
+ i386_cygwin_in_solib_call_trampoline);
+ set_gdbarch_skip_trampoline_code (gdbarch, i386_cygwin_skip_trampoline_code);
+
tdep->struct_return = reg_struct_return;
}