[libiberty patch] Fix PGO bootstrap

https://gcc.gnu.org/ml/gcc-patches/2018-08/msg01386.html
	PR driver/87056
	* pex-unix.c (pex_unix_exec_child): Duplicate bad_fn into local
	scopes to avoid potential clobber.

Co-Authored-By: Martin Liska <mliska@suse.cz>

From-SVN: r263807

libiberty/ChangeLog

+2018-08-23  Nathan Sidwell  <nathan@acm.org>
+	    Martin Liska  <mliska@suse.cz>
+
+	PR driver/87056
+	* pex-unix.c (pex_unix_exec_child): Duplicate bad_fn into local
+	scopes to avoid potential clobber.
+
 2018-08-20  Nathan Sidwell  <nathan@acm.org>
 
 	* pex-unix.c (pex_child_error): Delete.

libiberty/pex-unix.c

@@ -582,8 +582,6 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
      issues.   */
   char **save_environ = environ;
 
-  const char *bad_fn = NULL;
-
   for (retries = 0; retries < 4; ++retries)
     {
       pid = vfork ();
@@ -602,6 +600,9 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
 
     case 0:
       /* Child process.  */
+      {
+	const char *bad_fn = NULL;
+
 	if (!bad_fn && in != STDIN_FILE_NO)
 	  {
 	    if (dup2 (in, STDIN_FILE_NO) < 0)
@@ -654,9 +655,8 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
 
 	/* Something failed, report an error.  We don't use stdio
 	   routines, because we might be here due to a vfork call.  */
-      {
 	ssize_t retval = 0;
-	int err = errno;
+	int eno = errno;
 	
 #define writeerr(s) (retval |= write (STDERR_FILE_NO, s, strlen (s)))
 	writeerr (obj->pname);
@@ -665,7 +665,7 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
 	writeerr ("': ");
 	writeerr (bad_fn);
 	writeerr (": ");
-	writeerr (xstrerror (err));
+	writeerr (xstrerror (eno));
 	writeerr ("\n");
 #undef writeerr
 
@@ -677,12 +677,14 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
 
     default:
       /* Parent process.  */
+      {
+	const char *bad_fn = NULL;
 	
-      /* Restore environ.
-	 Note that the parent either doesn't run until the child execs/exits
-	 (standard vfork behaviour), or if it does run then vfork is behaving
-	 more like fork.  In either case we needn't worry about clobbering
-	 the child's copy of environ.  */
+	/* Restore environ.  Note that the parent either doesn't run
+	   until the child execs/exits (standard vfork behaviour), or
+	   if it does run then vfork is behaving more like fork.  In
+	   either case we needn't worry about clobbering the child's
+	   copy of environ.  */
 	environ = save_environ;
 
 	if (!bad_fn && in != STDIN_FILE_NO)
@@ -701,6 +703,7 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
 	    *errmsg = bad_fn;
 	    return (pid_t) -1;
 	  }
+      }
 
       return pid;
     }