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Date: Fri, 01 Jun 2012 18:05:00 -0000
From: Jan Kratochvil <jan.kratochvil@redhat.com>
To: Pedro Alves <palves@redhat.com>
Cc: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>,        gdb-patches@sourceware.org
Subject: Re: [PATCH] solib-svr4: Avoid unwanted shlib internal BPs When debugging Linux kernel or u-boot
Message-ID: <20120601172214.GA21236@host2.jankratochvil.net>
References: <1338562868-22411-1-git-send-email-Joakim.Tjernlund@transmode.se> <4FC8EC08.1060609@redhat.com>
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On Fri, 01 Jun 2012 18:21:28 +0200, Pedro Alves wrote:
> --- a/gdb/solib-svr4.c
> +++ b/gdb/solib-svr4.c
> @@ -1707,7 +1707,7 @@ enable_break (struct svr4_info *info, int from_tty)
>  	}
>      }
> 
> -  if (!current_inferior ()->attach_flag)
> +  if (interp_name != NULL && !current_inferior ()->attach_flag)
>      {
>        for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
>  	{

It has a regression in the case below.

OTOH one has to strip _start to make it a regression as with _start GDB did not
catch startup libraries even before.

This is why I suggested to omit only "__start" and "_start" but not "main" if
INTERP_NAME == NULL.

But maybe so broken systems are not so common nowadays to still care about
them.


Regards,
Jan


==> 53.C <==
#include <dlfcn.h>
#include <assert.h>
#include <stdio.h>
static void *lib;
class C {
public:
  C();
} c;
C::C() {
  lib = dlopen ("./53l.so", RTLD_NOW);
  assert(lib);
  puts("opened");
}
int main () {
  void (*fp)(void)=(void (*)(void))dlsym(lib,"l");
  assert(fp);
  fp();
}

==> 53l.C <==
#include <stdio.h>
class D {
public:
  D();
} d;
D::D() {
  puts ("in-library before-main");
}
extern "C" void l(void) {
  puts ("in-library after-main");
}

$ ./gdb-unpatched ./53 -ex 'set breakpoint pending on' -ex 'b l' -ex run 
Breakpoint 1, 0x00007ffff7dfd71e in l () from ./53l.so
(gdb) _

$ ./gdb-patched ./53 -ex 'set breakpoint pending on' -ex 'b l' -ex run 
[Inferior 1 (process 2188) exited normally]
(gdb) _