[libiberty] Use pipe inside pex_run

https://gcc.gnu.org/ml/gcc-patches/2018-10/msg00039.html
	* configure.ac (checkfuncs): Add pipe2.
	* config.in, configure: Rebuilt.
	* pex-unix.c (pex_unix_exec_child): Comminicate errors from child
	to parent with a pipe, when possible.

From-SVN: r264769

diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog
index 294bcb6..b2e833c 100644 (file)
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,10 @@
+2018-10-01  Nathan Sidwell  <nathan@acm.org>
+
+       * configure.ac (checkfuncs): Add pipe2.
+       * config.in, configure: Rebuilt.
+       * pex-unix.c (pex_unix_exec_child): Comminicate errors from child
+       to parent with a pipe, when possible.
+
 2018-08-23  Nathan Sidwell  <nathan@acm.org>
            Martin Liska  <mliska@suse.cz>
 

diff --git a/libiberty/config.in b/libiberty/config.in
index 66c78e8..c7b4725 100644 (file)
--- a/libiberty/config.in
+++ b/libiberty/config.in
@@ -195,6 +195,9 @@
 /* Define to 1 if you have the `on_exit' function. */
 #undef HAVE_ON_EXIT
 
+/* Define to 1 if you have the `pipe2' function. */
+#undef HAVE_PIPE2
+
 /* Define to 1 if you have the <process.h> header file. */
 #undef HAVE_PROCESS_H
 

diff --git a/libiberty/configure b/libiberty/configure
index ccadfaa..03ff394 100755 (executable)
--- a/libiberty/configure
+++ b/libiberty/configure
@@ -5727,7 +5727,7 @@ funcs="$funcs setproctitle"
 vars="sys_errlist sys_nerr sys_siglist"
 
 checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
- getsysinfo gettimeofday on_exit psignal pstat_getdynamic pstat_getstatic \
+ getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
  realpath setrlimit sbrk spawnve spawnvpe strerror strsignal sysconf sysctl \
  sysmp table times wait3 wait4"
 
@@ -5743,7 +5743,7 @@ if test "x" = "y"; then
     index insque \
     memchr memcmp memcpy memmem memmove memset mkstemps \
     on_exit \
-    psignal pstat_getdynamic pstat_getstatic putenv \
+    pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
     random realpath rename rindex \
     sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
      stpcpy stpncpy strcasecmp strchr strdup \

diff --git a/libiberty/configure.ac b/libiberty/configure.ac
index 6917cfa..59c45c9 100644 (file)
--- a/libiberty/configure.ac
+++ b/libiberty/configure.ac
@@ -391,7 +391,7 @@ funcs="$funcs setproctitle"
 vars="sys_errlist sys_nerr sys_siglist"
 
 checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
- getsysinfo gettimeofday on_exit psignal pstat_getdynamic pstat_getstatic \
+ getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
  realpath setrlimit sbrk spawnve spawnvpe strerror strsignal sysconf sysctl \
  sysmp table times wait3 wait4"
 
@@ -407,7 +407,7 @@ if test "x" = "y"; then
     index insque \
     memchr memcmp memcpy memmem memmove memset mkstemps \
     on_exit \
-    psignal pstat_getdynamic pstat_getstatic putenv \
+    pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
     random realpath rename rindex \
     sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
      stpcpy stpncpy strcasecmp strchr strdup \

diff --git a/libiberty/pex-unix.c b/libiberty/pex-unix.c
index 703010b..0f283e6 100644 (file)
--- a/libiberty/pex-unix.c
+++ b/libiberty/pex-unix.c
@@ -569,6 +569,38 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
                     int toclose, const char **errmsg, int *err)
 {
   pid_t pid = -1;
+  /* Tuple to communicate error from child to parent.  We can safely
+     transfer string literal pointers as both run with identical
+     address mappings.  */
+  struct fn_err 
+  {
+    const char *fn;
+    int err;
+  };
+  volatile int do_pipe = 0;
+  volatile int pipes[2]; /* [0]:reader,[1]:writer.  */
+#ifdef O_CLOEXEC
+  do_pipe = 1;
+#endif
+  if (do_pipe)
+    {
+#ifdef HAVE_PIPE2
+      if (pipe2 ((int *)pipes, O_CLOEXEC))
+       do_pipe = 0;
+#else
+      if (pipe ((int *)pipes))
+       do_pipe = 0;
+      else
+       {
+         if (fcntl (pipes[1], F_SETFD, FD_CLOEXEC) == -1)
+           {
+             close (pipes[0]);
+             close (pipes[1]);
+             do_pipe = 0;
+           }
+       }
+#endif
+    }
 
   /* We declare these to be volatile to avoid warnings from gcc about
      them being clobbered by vfork.  */
@@ -579,8 +611,9 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
      This clobbers the parent's environ so we need to restore it.
      It would be nice to use one of the exec* functions that takes an
      environment as a parameter, but that may have portability
-     issues.   */
-  char **save_environ = environ;
+     issues.  It is marked volatile so the child doesn't consider it a
+     dead variable and therefore clobber where ever it is stored.  */
+  char **volatile save_environ = environ;
 
   for (retries = 0; retries < 4; ++retries)
     {
@@ -594,6 +627,11 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
   switch (pid)
     {
     case -1:
+      if (do_pipe)
+       {
+         close (pipes[0]);
+         close (pipes[1]);
+       }
       *err = errno;
       *errmsg = VFORK_STRING;
       return (pid_t) -1;
@@ -601,40 +639,43 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
     case 0:
       /* Child process.  */
       {
-       const char *bad_fn = NULL;
+       struct fn_err failed;
+       failed.fn = NULL;
 
-       if (!bad_fn && in != STDIN_FILE_NO)
+       if (do_pipe)
+         close (pipes[0]);
+       if (!failed.fn && in != STDIN_FILE_NO)
          {
            if (dup2 (in, STDIN_FILE_NO) < 0)
-             bad_fn = "dup2";
+             failed.fn = "dup2", failed.err = errno;
            else if (close (in) < 0)
-             bad_fn = "close";
+             failed.fn = "close", failed.err = errno;
          }
-       if (!bad_fn && out != STDOUT_FILE_NO)
+       if (!failed.fn && out != STDOUT_FILE_NO)
          {
            if (dup2 (out, STDOUT_FILE_NO) < 0)
-             bad_fn = "dup2";
+             failed.fn = "dup2", failed.err = errno;
            else if (close (out) < 0)
-             bad_fn = "close";
+             failed.fn = "close", failed.err = errno;
          }
-       if (!bad_fn && errdes != STDERR_FILE_NO)
+       if (!failed.fn && errdes != STDERR_FILE_NO)
          {
            if (dup2 (errdes, STDERR_FILE_NO) < 0)
-             bad_fn = "dup2";
+             failed.fn = "dup2", failed.err = errno;
            else if (close (errdes) < 0)
-             bad_fn = "close";
+             failed.fn = "close", failed.err = errno;
          }
-       if (!bad_fn && toclose >= 0)
+       if (!failed.fn && toclose >= 0)
          {
            if (close (toclose) < 0)
-             bad_fn = "close";
+             failed.fn = "close", failed.err = errno;
          }
-       if (!bad_fn && (flags & PEX_STDERR_TO_STDOUT) != 0)
+       if (!failed.fn && (flags & PEX_STDERR_TO_STDOUT) != 0)
          {
            if (dup2 (STDOUT_FILE_NO, STDERR_FILE_NO) < 0)
-             bad_fn = "dup2";
+             failed.fn = "dup2", failed.err = errno;
          }
-       if (!bad_fn)
+       if (!failed.fn)
          {
            if (env)
              /* NOTE: In a standard vfork implementation this clobbers
@@ -644,30 +685,35 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
            if ((flags & PEX_SEARCH) != 0)
              {
                execvp (executable, to_ptr32 (argv));
-               bad_fn = "execvp";
+               failed.fn = "execvp", failed.err = errno;
              }
            else
              {
                execv (executable, to_ptr32 (argv));
-               bad_fn = "execv";
+               failed.fn = "execv", failed.err = errno;
              }
          }
 
        /* 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 eno = errno;
-       
+
+       if (!do_pipe
+           || write (pipes[1], &failed, sizeof (failed)) != sizeof (failed))
+         {
+           /* The parent will not see our scream above, so write to
+              stdout.  */
 #define writeerr(s) (retval |= write (STDERR_FILE_NO, s, strlen (s)))
-       writeerr (obj->pname);
-       writeerr (": error trying to exec '");
-       writeerr (executable);
-       writeerr ("': ");
-       writeerr (bad_fn);
-       writeerr (": ");
-       writeerr (xstrerror (eno));
-       writeerr ("\n");
+           writeerr (obj->pname);
+           writeerr (": error trying to exec '");
+           writeerr (executable);
+           writeerr ("': ");
+           writeerr (failed.fn);
+           writeerr (": ");
+           writeerr (xstrerror (failed.err));
+           writeerr ("\n");
 #undef writeerr
+         }
 
        /* Exit with -2 if the error output failed, too.  */
        _exit (retval < 0 ? -2 : -1);
@@ -678,8 +724,6 @@ 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
@@ -687,24 +731,34 @@ pex_unix_exec_child (struct pex_obj *obj, int flags, const char *executable,
           copy of environ.  */
        environ = save_environ;
 
-       if (!bad_fn && in != STDIN_FILE_NO)
+       struct fn_err failed;
+       failed.fn = NULL;
+       if (do_pipe)
+         {
+           close (pipes[1]);
+           ssize_t len = read (pipes[0], &failed, sizeof (failed));
+           if (len < 0)
+             failed.fn = NULL;
+           close (pipes[0]);
+         }
+
+       if (!failed.fn && in != STDIN_FILE_NO)
          if (close (in) < 0)
-           bad_fn = "close";
-       if (!bad_fn && out != STDOUT_FILE_NO)
+           failed.fn = "close", failed.err = errno;
+       if (!failed.fn && out != STDOUT_FILE_NO)
          if (close (out) < 0)
-           bad_fn = "close";
-       if (!bad_fn && errdes != STDERR_FILE_NO)
+           failed.fn = "close", failed.err = errno;
+       if (!failed.fn && errdes != STDERR_FILE_NO)
          if (close (errdes) < 0)
-           bad_fn = "close";
+           failed.fn = "close", failed.err = errno;
 
-       if (bad_fn)
+       if (failed.fn)
          {
-           *err = errno;
-           *errmsg = bad_fn;
+           *err = failed.err;
+           *errmsg = failed.fn;
            return (pid_t) -1;
          }
       }
-
       return pid;
     }
 }