[patch] procfs.c: Fix a build failure on SPARC.

[patch] procfs.c: Fix a build failure on SPARC.

[Kazu Hirata]

Hi,

Attached is a patch to fix a build failure on SPARC.

Without this patch, I get several errors like so:

  error: dereferencing pointer 'mysinfo' does break strict-aliasing rules

when building gdb with gcc-4.4.

This patch, which Pedro helped me develop, fixes the problem by
rearranging:

  struct {
    procfs_ctl_t cmd;
    /* Use char array to avoid alignment issues.  */
    char sinfo[sizeof (gdb_siginfo_t)];
  } arg;
  gdb_siginfo_t *mysinfo;
  mysinfo = (gdb_siginfo_t *) &arg.sinfo;
  mysinfo->si_signo = signo;

to:

  struct {
    procfs_ctl_t cmd;
    /* Use char array to avoid alignment issues.  */
    char sinfo[sizeof (gdb_siginfo_t)];
  } arg;
  gdb_siginfo_t mysinfo;
  mysinfo.si_signo = signo;
  memcpy (arg.sinfo, &mysinfo, sizeof (gdb_siginfo_t));

Note that we populate mysinfo before copying it to arg.sinfo.

Tested by building sparc-solaris2.8.  OK to apply?

Kazu Hirata

2009-07-31  Kazu Hirata  <kazu@codesourcery.com>

	* procfs.c (proc_set_current_signal): Populate mysinfo before
	copying it to arg.
	(proc_clear_current_signal): Likewise.
	(proc_set_watchpoint): Populate pwatch before copying it to arg.

Index: gdb/procfs.c
===================================================================
RCS file: /cvs/src/src/gdb/procfs.c,v
retrieving revision 1.114
diff -u -d -p -r1.114 procfs.c
--- gdb/procfs.c	2 Jul 2009 17:25:58 -0000	1.114
+++ gdb/procfs.c	31 Jul 2009 20:48:51 -0000
@@ -2505,7 +2505,7 @@ proc_set_current_signal (procinfo *pi, i
     /* Use char array to avoid alignment issues.  */
     char sinfo[sizeof (gdb_siginfo_t)];
   } arg;
-  gdb_siginfo_t *mysinfo;
+  gdb_siginfo_t mysinfo;
   ptid_t wait_ptid;
   struct target_waitstatus wait_status;
 
@@ -2530,7 +2530,6 @@ proc_set_current_signal (procinfo *pi, i
 #endif
 
   /* The pointer is just a type alias.  */
-  mysinfo = (gdb_siginfo_t *) &arg.sinfo;
   get_last_target_status (&wait_ptid, &wait_status);
   if (ptid_equal (wait_ptid, inferior_ptid)
       && wait_status.kind == TARGET_WAITKIND_STOPPED
@@ -2545,16 +2544,17 @@ proc_set_current_signal (procinfo *pi, i
     /* Use the siginfo associated with the signal being
        redelivered.  */
 #ifdef NEW_PROC_API
-    memcpy (mysinfo, &pi->prstatus.pr_lwp.pr_info, sizeof (gdb_siginfo_t));
+    memcpy (arg.sinfo, &pi->prstatus.pr_lwp.pr_info, sizeof (gdb_siginfo_t));
 #else
-    memcpy (mysinfo, &pi->prstatus.pr_info, sizeof (gdb_siginfo_t));
+    memcpy (arg.sinfo, &pi->prstatus.pr_info, sizeof (gdb_siginfo_t));
 #endif
   else
     {
-      mysinfo->si_signo = signo;
-      mysinfo->si_code  = 0;
-      mysinfo->si_pid   = getpid ();       /* ?why? */
-      mysinfo->si_uid   = getuid ();       /* ?why? */
+      mysinfo.si_signo = signo;
+      mysinfo.si_code  = 0;
+      mysinfo.si_pid   = getpid ();       /* ?why? */
+      mysinfo.si_uid   = getuid ();       /* ?why? */
+      memcpy (arg.sinfo, &mysinfo, sizeof (gdb_siginfo_t));
     }
 
 #ifdef NEW_PROC_API
@@ -2597,16 +2597,16 @@ proc_clear_current_signal (procinfo *pi)
       /* Use char array to avoid alignment issues.  */
       char sinfo[sizeof (gdb_siginfo_t)];
     } arg;
-    gdb_siginfo_t *mysinfo;
+    gdb_siginfo_t mysinfo;
 
     arg.cmd = PCSSIG;
     /* The pointer is just a type alias.  */
-    mysinfo = (gdb_siginfo_t *) &arg.sinfo;
-    mysinfo->si_signo = 0;
-    mysinfo->si_code  = 0;
-    mysinfo->si_errno = 0;
-    mysinfo->si_pid   = getpid ();       /* ?why? */
-    mysinfo->si_uid   = getuid ();       /* ?why? */
+    mysinfo.si_signo = 0;
+    mysinfo.si_code  = 0;
+    mysinfo.si_errno = 0;
+    mysinfo.si_pid   = getpid ();       /* ?why? */
+    mysinfo.si_uid   = getuid ();       /* ?why? */
+    memcpy (arg.sinfo, &mysinfo, sizeof (gdb_siginfo_t));
 
     win = (write (pi->ctl_fd, (void *) &arg, sizeof (arg)) == sizeof (arg));
   }
@@ -2917,25 +2917,25 @@ proc_set_watchpoint (procinfo *pi, CORE_
     procfs_ctl_t cmd;
     char watch[sizeof (prwatch_t)];
   } arg;
-  prwatch_t *pwatch;
+  prwatch_t pwatch;
 
-  pwatch            = (prwatch_t *) &arg.watch;
   /* NOTE: cagney/2003-02-01: Even more horrible hack.  Need to
      convert a target address into something that can be stored in a
      native data structure.  */
 #ifdef PCAGENT	/* Horrible hack: only defined on Solaris 2.6+ */
-  pwatch->pr_vaddr  = (uintptr_t) procfs_address_to_host_pointer (addr);
+  pwatch.pr_vaddr  = (uintptr_t) procfs_address_to_host_pointer (addr);
 #else
-  pwatch->pr_vaddr  = (caddr_t) procfs_address_to_host_pointer (addr);
+  pwatch.pr_vaddr  = (caddr_t) procfs_address_to_host_pointer (addr);
 #endif
-  pwatch->pr_size   = len;
-  pwatch->pr_wflags = wflags;
+  pwatch.pr_size   = len;
+  pwatch.pr_wflags = wflags;
 #if defined(NEW_PROC_API) && defined (PCWATCH)
   arg.cmd = PCWATCH;
+  memcpy (arg.watch, &pwatch, sizeof (prwatch_t));
   return (write (pi->ctl_fd, &arg, sizeof (arg)) == sizeof (arg));
 #else
 #if defined (PIOCSWATCH)
-  return (ioctl (pi->ctl_fd, PIOCSWATCH, pwatch) >= 0);
+  return (ioctl (pi->ctl_fd, PIOCSWATCH, &pwatch) >= 0);
 #else
   return 0;	/* Fail */
 #endif

Re: [patch] procfs.c: Fix a build failure on SPARC.

[Pedro Alves]

On Friday 31 July 2009 21:50:51, Kazu Hirata wrote:

> Attached is a patch to fix a build failure on SPARC.
> 
> Without this patch, I get several errors like so:
> 
>   error: dereferencing pointer 'mysinfo' does break strict-aliasing rules
> 
> when building gdb with gcc-4.4.

...

> Tested by building sparc-solaris2.8.  OK to apply?

Looks good to me, go ahead.  Thanks!

-- 
Pedro Alves