libiberty: Use posix_spawn in pex-unix when available.

Hi,

This patch implements pex_unix_exec_child using posix_spawn when
available.

This should especially benefit recent macOS (where vfork just calls
fork), but should have equivalent or faster performance on all
platforms.
In addition, the implementation is substantially simpler than the
vfork+exec code path.

Tested on x86_64-linux.

v2: Fix error handling (previously the function would be run twice in
case of error), and don't use a macro that changes control flow.

v3: Match file style for error-handling blocks, don't close
in/out/errdes on error, and check close() for errors.

libiberty/
	* configure.ac (AC_CHECK_HEADERS): Add spawn.h.
	(checkfuncs): Add posix_spawn, posix_spawnp.
	(AC_CHECK_FUNCS): Add posix_spawn, posix_spawnp.
	* aclocal.m4, configure, config.in: Rebuild.
	* pex-unix.c [HAVE_POSIX_SPAWN] (pex_unix_exec_child): New function.

gcc/libiberty/aclocal.m4

@@ -1,6 +1,6 @@
-# generated automatically by aclocal 1.15.1 -*- Autoconf -*-
+# generated automatically by aclocal 1.16.5 -*- Autoconf -*-
 
-# Copyright (C) 1996-2017 Free Software Foundation, Inc.
+# Copyright (C) 1996-2021 Free Software Foundation, Inc.
 
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,

gcc/libiberty/config.in

@@ -198,6 +198,12 @@
 /* Define to 1 if you have the `pipe2' function. */
 #undef HAVE_PIPE2
 
+/* Define to 1 if you have the `posix_spawn' function. */
+#undef HAVE_POSIX_SPAWN
+
+/* Define to 1 if you have the `posix_spawnp' function. */
+#undef HAVE_POSIX_SPAWNP
+
 /* Define to 1 if you have the <process.h> header file. */
 #undef HAVE_PROCESS_H
 
@@ -249,6 +255,9 @@
 /* Define to 1 if you have the `spawnvpe' function. */
 #undef HAVE_SPAWNVPE
 
+/* Define to 1 if you have the <spawn.h> header file. */
+#undef HAVE_SPAWN_H
+
 /* Define to 1 if you have the <stdint.h> header file. */
 #undef HAVE_STDINT_H
 

gcc/libiberty/configure

@@ -5517,7 +5517,7 @@ host_makefile_frag=${frag}
 # It's OK to check for header files.  Although the compiler may not be
 # able to link anything, it had better be able to at least compile
 # something.
-for ac_header in sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h
+for ac_header in sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h spawn.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_preproc "$LINENO" "$ac_header" "$as_ac_Header"
@@ -6026,7 +6026,8 @@ funcs="$funcs setproctitle"
 vars="sys_errlist sys_nerr sys_siglist"
 
 checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
- getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
+ getsysinfo gettimeofday on_exit pipe2 posix_spawn posix_spawnp psignal \
+ pstat_getdynamic pstat_getstatic \
  realpath setrlimit spawnve spawnvpe strerror strsignal sysconf sysctl \
  sysmp table times wait3 wait4"
 
@@ -6049,7 +6050,8 @@ if test "x" = "y"; then
     index insque \
     memchr memcmp memcpy memmem memmove memset mkstemps \
     on_exit \
-    pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
+    pipe2 posix_spawn posix_spawnp psignal \
+    pstat_getdynamic pstat_getstatic putenv \
     random realpath rename rindex \
     sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
      stpcpy stpncpy strcasecmp strchr strdup \

gcc/libiberty/configure.ac

@@ -277,7 +277,7 @@ AC_SUBST_FILE(host_makefile_frag)
 # It's OK to check for header files.  Although the compiler may not be
 # able to link anything, it had better be able to at least compile
 # something.
-AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h)
+AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h spawn.h)
 AC_HEADER_SYS_WAIT
 AC_HEADER_TIME
 
@@ -400,7 +400,8 @@ funcs="$funcs setproctitle"
 vars="sys_errlist sys_nerr sys_siglist"
 
 checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
- getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
+ getsysinfo gettimeofday on_exit pipe2 posix_spawn posix_spawnp psignal \
+ pstat_getdynamic pstat_getstatic \
  realpath setrlimit spawnve spawnvpe strerror strsignal sysconf sysctl \
  sysmp table times wait3 wait4"
 
@@ -423,7 +424,8 @@ if test "x" = "y"; then
     index insque \
     memchr memcmp memcpy memmem memmove memset mkstemps \
     on_exit \
-    pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
+    pipe2 posix_spawn posix_spawnp psignal \
+    pstat_getdynamic pstat_getstatic putenv \
     random realpath rename rindex \
     sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
      stpcpy stpncpy strcasecmp strchr strdup \

gcc/libiberty/pex-unix.c

@@ -58,6 +58,9 @@ extern int errno;
 #ifdef HAVE_PROCESS_H
 #include <process.h>
 #endif
+#ifdef HAVE_SPAWN_H
+#include <spawn.h>
+#endif
 
 #ifdef vfork /* Autoconf may define this to fork for us. */
 # define VFORK_STRING "fork"
@@ -559,6 +562,171 @@ pex_unix_exec_child (struct pex_obj *obj ATTRIBUTE_UNUSED,
   return (pid_t) -1;
 }
 
+#elif defined(HAVE_POSIX_SPAWN) && defined(HAVE_POSIX_SPAWNP)
+/* Implementation of pex->exec_child using posix_spawn.            */
+
+static pid_t
+pex_unix_exec_child (struct pex_obj *obj ATTRIBUTE_UNUSED,
+		     int flags, const char *executable,
+		     char * const * argv, char * const * env,
+		     int in, int out, int errdes,
+		     int toclose, const char **errmsg, int *err)
+{
+  int ret;
+  pid_t pid = -1;
+  posix_spawnattr_t attr;
+  posix_spawn_file_actions_t actions;
+  int attr_initialized = 0, actions_initialized = 0;
+
+  *err = 0;
+
+  ret = posix_spawnattr_init (&attr);
+  if (ret)
+    {
+      *err = ret;
+      *errmsg = "posix_spawnattr_init";
+      goto exit;
+    }
+  attr_initialized = 1;
+
+  /* Use vfork() on glibc <=2.24. */
+#ifdef POSIX_SPAWN_USEVFORK
+  ret = posix_spawnattr_setflags (&attr, POSIX_SPAWN_USEVFORK);
+  if (ret)
+    {
+      *err = ret;
+      *errmsg = "posix_spawnattr_setflags";
+      goto exit;
+    }
+#endif
+
+  ret = posix_spawn_file_actions_init (&actions);
+  if (ret)
+    {
+      *err = ret;
+      *errmsg = "posix_spawn_file_actions_init";
+      goto exit;
+    }
+  actions_initialized = 1;
+
+  if (in != STDIN_FILE_NO)
+    {
+      ret = posix_spawn_file_actions_adddup2 (&actions, in, STDIN_FILE_NO);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_adddup2";
+	  goto exit;
+	}
+
+      ret = posix_spawn_file_actions_addclose (&actions, in);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_addclose";
+	  goto exit;
+	}
+    }
+
+  if (out != STDOUT_FILE_NO)
+    {
+      ret = posix_spawn_file_actions_adddup2 (&actions, out, STDOUT_FILE_NO);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_adddup2";
+	  goto exit;
+	}
+
+      ret = posix_spawn_file_actions_addclose (&actions, out);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_addclose";
+	  goto exit;
+	}
+    }
+
+  if (errdes != STDERR_FILE_NO)
+    {
+      ret = posix_spawn_file_actions_adddup2 (&actions, errdes, STDERR_FILE_NO);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_adddup2";
+	  goto exit;
+	}
+
+      ret = posix_spawn_file_actions_addclose (&actions, errdes);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_addclose";
+	  goto exit;
+	}
+    }
+
+  if (toclose >= 0)
+    {
+      ret = posix_spawn_file_actions_addclose (&actions, toclose);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_addclose";
+	  goto exit;
+	}
+    }
+
+  if ((flags & PEX_STDERR_TO_STDOUT) != 0)
+    {
+      ret = posix_spawn_file_actions_adddup2 (&actions, STDOUT_FILE_NO, STDERR_FILE_NO);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn_file_actions_adddup2";
+	  goto exit;
+	}
+    }
+
+  if ((flags & PEX_SEARCH) != 0)
+    {
+      ret = posix_spawnp (&pid, executable, &actions, &attr, argv, env ? env : environ);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawnp";
+	  goto exit;
+	}
+    }
+  else
+    {
+      ret = posix_spawn (&pid, executable, &actions, &attr, argv, env ? env : environ);
+      if (ret)
+	{
+	  *err = ret;
+	  *errmsg = "posix_spawn";
+	  goto exit;
+	}
+    }
+
+exit:
+  if (actions_initialized)
+    posix_spawn_file_actions_destroy (&actions);
+  if (attr_initialized)
+    posix_spawnattr_destroy (&attr);
+
+  if (!*err && in != STDIN_FILE_NO)
+    if (close (in))
+      *errmsg = "close", *err = errno, pid = -1;
+  if (!*err && out != STDOUT_FILE_NO)
+    if (close (out))
+      *errmsg = "close", *err = errno, pid = -1;
+  if (!*err && errdes != STDERR_FILE_NO)
+    if (close (errdes))
+      *errmsg = "close", *err = errno, pid = -1;
+
+  return pid;
+}
 #else
 /* Implementation of pex->exec_child using standard vfork + exec.  */