execl: New module.

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

1 files changed, 82 insertions, 0 deletions

diff --git a/lib/execl.c b/lib/execl.c
new file mode 100644
index 0000000000..d1df0c0861
--- /dev/null
+++ b/lib/execl.c
@@ -0,0 +1,82 @@
+/* execl() 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
+execl (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 *);
+    va_end (args);
+  }
+
+  /* Invoke execv.  */
+  execv (program, argv);
+
+  /* If execv returned, it must have failed.  */
+  int saved_errno = errno;
+  freea (argv);
+  errno = saved_errno;
+  return -1;
+}