execle: New module.

* lib/execle.c: New file.
* m4/execle.m4: New file.
* modules/execle: New file.
* doc/posix-functions/execle.texi: Mention more Windows problems and the
new module.

5 files changed, 150 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 7f5c99b902..6a8939cef5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2020-12-26  Bruno Haible  <bruno@clisp.org>
 
+	execle: New module.
+	* lib/execle.c: New file.
+	* m4/execle.m4: New file.
+	* modules/execle: New file.
+	* doc/posix-functions/execle.texi: Mention more Windows problems and the
+	new module.
+
 	execl: Add tests.
 	* tests/test-execl-main.c: New file.
 	* tests/test-execl.sh: New file.
diff --git a/doc/posix-functions/execle.texi b/doc/posix-functions/execle.texi
index 04ef7c2563..e556260675 100644
--- a/doc/posix-functions/execle.texi
+++ b/doc/posix-functions/execle.texi
@@ -4,19 +4,30 @@
 
 POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/execle.html}
 
-Gnulib module: ---
+Gnulib module: execle
 
 Portability problems fixed by Gnulib:
 @itemize
+@item
+On Windows platforms (excluding Cygwin), this function does not pass
+command-line arguments correctly if they contain space, tab, backslash,
+or double-quote characters.
+@item
+On Windows platforms (excluding Cygwin), this function spawns an asynchronous
+child process and then exits the current process immediately.  As a
+consequence, the parent of the current process 1. may incorrectly proceed
+as if its child had exited, and 2. will never see the child's exit status.
+@item
+On Windows platforms (excluding Cygwin), the return type of this function is
+@code{intptr_t}, not @code{int}.
 @end itemize
 
+Note: The Gnulib replacement for this function is not async-safe, that is,
+it must not be invoked from a signal handler.
+
 Portability problems not fixed by Gnulib:
 @itemize
 @item
 On some platforms, a script without executable permission is still run:
 Cygwin 1.5.x.
-@item
-On Windows platforms (excluding Cygwin), this function operates by spawning
-and then by exiting the current process, which means the current
-process's parent may incorrectly proceed as if its child had exited.
 @end itemize
diff --git a/lib/execle.c b/lib/execle.c
new file mode 100644
index 0000000000..8e10d8a6a8
--- /dev/null
+++ b/lib/execle.c
@@ -0,0 +1,83 @@
+/* execle() function: Execute a program, replacing the current process.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2020.  */
+
+/* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
+   may optimize away the arg0 == NULL test below.  */
+#define _GL_ARG_NONNULL(params)
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdarg.h>
+
+#include "malloca.h"
+
+int
+execle (const char *program, const char *arg0, ...)
+{
+  va_list args;
+
+  /* The callee is not expecting a NULL argv[0].  */
+  if (arg0 == NULL)
+    {
+      errno = EINVAL;
+      return -1;
+    }
+
+  /* Count the number of arguments (including arg0 and the trailing NULL).  */
+  size_t count = 1;
+  va_start (args, arg0);
+  for (;;)
+    {
+      count++;
+      if (va_arg (args, const char *) == NULL)
+        break;
+    }
+  va_end (args);
+
+  /* Allocate the argument vector.  */
+  const char **argv = (const char **) malloca (count * sizeof (const char *));
+  if (argv == NULL)
+    {
+      errno = ENOMEM;
+      return -1;
+    }
+
+  /* Copy the arguments into the argument vector.  */
+  {
+    size_t i = 0;
+    argv[i++] = arg0;
+    va_start (args, arg0);
+    for (; i < count;)
+      argv[i++] = va_arg (args, const char *);
+  }
+  char * const *env = va_arg (args, char * const *);
+  va_end (args);
+
+  /* Invoke execve.  */
+  execve (program, argv, env);
+
+  /* If execve returned, it must have failed.  */
+  int saved_errno = errno;
+  freea (argv);
+  errno = saved_errno;
+  return -1;
+}
diff --git a/m4/execle.m4 b/m4/execle.m4
new file mode 100644
index 0000000000..47b273b4d1
--- /dev/null
+++ b/m4/execle.m4
@@ -0,0 +1,15 @@
+# execle.m4 serial 1
+dnl Copyright (C) 2020 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_EXECLE],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+
+  case "$host_os" in
+    mingw*) REPLACE_EXECLE=1 ;;
+  esac
+])
diff --git a/modules/execle b/modules/execle
new file mode 100644
index 0000000000..dd3c9ad961
--- /dev/null
+++ b/modules/execle
@@ -0,0 +1,29 @@
+Description:
+execle() function: Execute a program, replacing the current process.
+
+Files:
+lib/execle.c
+m4/execle.m4
+
+Depends-on:
+unistd
+execve          [test $REPLACE_EXECLE = 1]
+malloca         [test $REPLACE_EXECLE = 1]
+
+configure.ac:
+gl_FUNC_EXECLE
+if test $REPLACE_EXECLE = 1; then
+  AC_LIBOBJ([execle])
+fi
+gl_UNISTD_MODULE_INDICATOR([execle])
+
+Makefile.am:
+
+Include:
+<unistd.h>
+
+License:
+LGPLv2+
+
+Maintainer:
+all