http://sourceware.org/ml/binutils/2011-12/msg00298.html

Subject: [patch] Fix zero registers core files w/gcc-4.7

Hello H.J.,

there is a regression by:

	commit 2c9c556617a7de8657c25b512d272c26b070ae22

	Author: H.J. Lu <hjl.tools@gmail.com>

	Date:   Thu Jun 16 22:08:10 2011 +0000

	    Suport x32 gcore.

when built with -O2 by

	gcc (GCC) 4.7.0 20111223 (experimental)

	(not by 4.6.x)

as the code violates ISO C99 6.2.4 item 5 by using local variable outside of

its block, GCC optimizes out the second memcpy, keeping there only that

memset.

./gdb -nx ./gdb -ex start -ex 'gcore 1' -ex 'set confirm no' -ex q;gdb -nx ./gdb ./1 -ex q

will print:

Core was generated by `.../gdb/gdb'.

#0  0x0000000000000000 in ?? ()

No regressions on x86_64-fedora16-linux-gnu.

Probably obvious, OK to check it in?

Thanks,

Jan

bfd/

2011-12-23  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix zero registers core files when built by gcc-4.7.

	* elf64-x86-64.c (elf_x86_64_write_core_note): Remove variables p and

	size.  Call elfcore_write_note for the local variables.  Remove the

	final elfcore_write_note call.  Add NOTREACHED comments.

--- a/bfd/elf64-x86-64.c

+++ b/bfd/elf64-x86-64.c

@@ -420,8 +420,6 @@ elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,

 			    int note_type, ...)

 {

   const struct elf_backend_data *bed = get_elf_backend_data (abfd);

-  const void *p;

-  int size;

   va_list ap;

   const char *fname, *psargs;

   long pid;

@@ -445,8 +443,8 @@ elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,

 	  memset (&data, 0, sizeof (data));

 	  strncpy (data.pr_fname, fname, sizeof (data.pr_fname));

 	  strncpy (data.pr_psargs, psargs, sizeof (data.pr_psargs));

-	  p = (const void *) &dat;;

-	  size = sizeof (data);

+	  return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,

+				     &data, sizeof (data));

 	}

       else

 	{

@@ -454,10 +452,10 @@ elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,

 	  memset (&data, 0, sizeof (data));

 	  strncpy (data.pr_fname, fname, sizeof (data.pr_fname));

 	  strncpy (data.pr_psargs, psargs, sizeof (data.pr_psargs));

-	  p = (const void *) &dat;;

-	  size = sizeof (data);

+	  return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,

+				     &data, sizeof (data));

 	}

-      break;

+      /* NOTREACHED */

     case NT_PRSTATUS:

       va_start (ap, note_type);

@@ -475,8 +473,8 @@ elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,

 	      prstat.pr_pid = pid;

 	      prstat.pr_cursig = cursig;

 	      memcpy (&prstat.pr_reg, gregs, sizeof (prstat.pr_reg));

-	      p = (const void *) &prstat;

-	      size = sizeof (prstat);

+	      return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,

+					 &prstat, sizeof (prstat));

 	    }

 	  else

 	    {

@@ -485,8 +483,8 @@ elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,

 	      prstat.pr_pid = pid;

 	      prstat.pr_cursig = cursig;

 	      memcpy (&prstat.pr_reg, gregs, sizeof (prstat.pr_reg));

-	      p = (const void *) &prstat;

-	      size = sizeof (prstat);

+	      return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,

+					 &prstat, sizeof (prstat));

 	    }

 	}

       else

@@ -496,14 +494,11 @@ elf_x86_64_write_core_note (bfd *abfd, char *buf, int *bufsiz,

 	  prstat.pr_pid = pid;

 	  prstat.pr_cursig = cursig;

 	  memcpy (&prstat.pr_reg, gregs, sizeof (prstat.pr_reg));

-	  p = (const void *) &prstat;

-	  size = sizeof (prstat);

+	  return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type,

+				     &prstat, sizeof (prstat));

 	}

-      break;

     }

-

-  return elfcore_write_note (abfd, buf, bufsiz, "CORE", note_type, p,

-			     size);

+  /* NOTREACHED */

 }

 #endif