add exec functions

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 376 insertions, 0 deletions

diff --git a/src/unistd/exec.c b/src/unistd/exec.c
new file mode 100644
index 0000000..5c3584c
--- /dev/null
+++ b/src/unistd/exec.c
@@ -0,0 +1,376 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+#include <unistd.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <alloca.h>
+#include <string.h>
+#include <stdlib.h>
+
+
+
+/**
+ * The current environment variables.
+ */
+extern char** environ;
+
+
+
+/**
+ * Common code for the `execl*` functions.
+ * 
+ * @param   file        The first argument of said functions.
+ * @param   argv        The rest of the arguments of said functions;
+ *                      may conclude `envp`.
+ * @param   fetch_envp  Whether `argv` includes `envp`.
+ * @param   use_path    Whether $PATH may be used.
+ * 
+ * @throws              Any error specified for execve(2).
+ */
+static void vexec(const char* file, va_list argv, int fetch_envp, int use_path)
+{
+  char* const* envp = environ;
+  size_t n = 0, i;
+  va_list args;
+  char** argv_;
+  
+  va_copy(args, argv);
+  while (n++, va_arg(args, char*) != NULL)
+    break;
+  
+  if (fetch_envp)
+    envp = va_arg(args, char* const*);
+  
+  argv_ = alloca(n * sizeof(char*));
+  for (i = 0; i < n; i++)
+    argv_[i] = va_arg(args, char*);
+  
+  (void)(use_path ? execvpe : execve)(file, argv_, envp);
+}
+
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   path  The pathname of the file to execute.
+ * @param   ...   The arguments with which to execute the file.
+ *                The arguments should have the type `const char*`.
+ *                As a slibc extension, it can be empty.
+ *                This list shall be terminated by a `NULL` sentinel.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execl(const char* path, ... /*, NULL */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexec(path, argv, 0, 0);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   file  The pathname of the file to execute,
+ *                or the filename of a file in $PATH,
+ *                to execute.
+ * @param   ...   The arguments with which to execute the file.
+ *                The arguments should have the type `const char*`.
+ *                As a slibc extension, it can be empty.
+ *                This list shall be terminated by a `NULL` sentinel.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execlp(const char* file, ... /*, NULL */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexec(path, argv, 0, 1);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   path  The pathname of the file to execute.
+ * @param   ...   The arguments with which to execute the file.
+ *                The arguments should have the type `const char*`.
+ *                As a slibc extension, it can be empty.
+ *                This list shall be terminated by a `NULL` sentinel.
+ * @param   envp  The list of environment variables the new program shall
+ *                have set. Each element shall be foramtted $name=$value.
+ *                This list shall be `NULL`-terminated. The behaviour
+ *                is system-dependant if this argument is `NULL`.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execle(const char* path, ... /*, NULL, char* const envp[] */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexec(path, argv, 1, 0);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension, added for completeness.
+ * 
+ * @param   file  The pathname of the file to execute,
+ *                or the filename of a file in $PATH,
+ *                to execute.
+ * @param   ...   The arguments with which to execute the file.
+ *                The arguments should have the type `const char*`.
+ *                As a slibc extension, it can be empty.
+ *                This list shall be terminated by a `NULL` sentinel.
+ * @param   envp  The list of environment variables the new program shall
+ *                have set. Each element shall be foramtted $name=$value.
+ *                This list shall be `NULL`-terminated. The behaviour
+ *                is system-dependant if this argument is `NULL`.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execlpe(const char* file, ... /*, NULL, char* const envp[] */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexec(path, argv, 1, 1);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   path  The pathname of the file to execute.
+ * @param   argv  The arguments with which to execute the file.
+ *                This parameter should really have the type
+ *                `const char* const[]`, but that probably not
+ *                so because compiles take issue with casts
+ *                adding const to any pointer in the type
+ *                except the outmost pointer. This list shall
+ *                be `NULL`-terminated. The behaviour is
+ *                system-dependant if this argument is `NULL`.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execv(const char* path, char* const argv[])
+{
+  return execve(path, argv, environ);
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   file  The pathname of the file to execute,
+ *                or the filename of a file in $PATH,
+ *                to execute.
+ * @param   argv  The arguments with which to execute the file.
+ *                This parameter should really have the type
+ *                `const char* const[]`, but that probably not
+ *                so because compiles take issue with casts
+ *                adding const to any pointer in the type
+ *                except the outmost pointer. This list shall
+ *                be `NULL`-terminated. The behaviour is
+ *                system-dependant if this argument is `NULL`.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execvp(const char* file, char* const argv[])
+{
+  return execvpe(path, argv, environ);
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   path  The pathname of the file to execute.
+ * @param   argv  The arguments with which to execute the file.
+ *                This parameter should really have the type
+ *                `const char* const[]`, but that probably not
+ *                so because compiles take issue with casts
+ *                adding const to any pointer in the type
+ *                except the outmost pointer. This list shall
+ *                be `NULL`-terminated. The behaviour is
+ *                system-dependant if this argument is `NULL`.
+ * @param   envp  The list of environment variables the new program shall
+ *                have set. Each element shall be foramtted $name=$value.
+ *                This list shall be `NULL`-terminated. The behaviour
+ *                is system-dependant if this argument is `NULL`.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execve(const char* path, char* const argv[], char* const envp[])
+{
+  return errno = ENOTSUP, -1;
+  (void) path, (void) argv, (void) enpv;
+  /* TODO implement execve */
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a GNU-compliant slibc extension.
+ * 
+ * @param   file  The pathname of the file to execute,
+ *                or the filename of a file in $PATH,
+ *                to execute.
+ * @param   argv  The arguments with which to execute the file.
+ *                This parameter should really have the type
+ *                `const char* const[]`, but that probably not
+ *                so because compiles take issue with casts
+ *                adding const to any pointer in the type
+ *                except the outmost pointer. This list shall
+ *                be `NULL`-terminated. The behaviour is
+ *                system-dependant if this argument is `NULL`.
+ * @param   envp  The list of environment variables the new program shall
+ *                have set. Each element shall be foramtted $name=$value.
+ *                This list shall be `NULL`-terminated. The behaviour
+ *                is system-dependant if this argument is `NULL`.
+ * @return        This function does not return on success,
+ *                on error, -1 is returned and `errno` is
+ *                set to describe the error.
+ * 
+ * @throws        Any error specified for execve(2).
+ */
+int execvpe(const char* file, char* const argv[], char* const envp[])
+{
+  char* path = NULL;
+  char* path_cwd = NULL;
+  char* path_def = NULL;
+  char* path_env;
+  char* pathname = NULL;
+  char* p;
+  char* q;
+  size_t len = 0;
+  int eacces = 0;
+  int saved_errno;
+  
+  if (strchr(file, '/'))
+    return execve(file, argv, envp);
+  
+  if (!*file)
+    return errno = ENOENT, -1;
+  
+  path_env = getenv(PATH);
+  if (path_env == NULL)
+    {
+      path_cwd = get_current_dir_name();
+      if (path_cwd == NULL)
+	goto fail;
+      
+      len = confstr(_CS_PATH, NULL, 0);
+      if (len)
+	{
+	  path_def = malloc((1 + len) * sizeof(char));
+	  if (path_def == NULL)
+	    goto fail;
+	  *path_def = ':';
+	  if (confstr(_CS_PATH, path_def + 1, len))
+	    path_def = NULL, len = 0;
+	}
+      if (path_def == NULL)
+	path_def = ":/usr/local/bin:/bin:/usr/bin";
+      
+      path = malloc((strlen(path_cwd) + strlen(path_def) + 1) * sizeof(char));
+      if (path == NULL)
+	goto fail;
+      
+      stpcpy(stpcpy(path, path_cwd), path_def);
+      free(path_cwd), path_cwd = NULL;
+      if (len)
+	free(path_def), path_def = NULL;
+    }
+  else
+    if (path = strdup(path_env), path == NULL)
+      goto fail;
+  
+  pathname = malloc((strlen(path) + strlen(file) + 2) * sizeof(char));
+  
+  for (p = path; *p; p = q + 1)
+    {
+      q = strchr(p, ':');
+      if (q == p)
+	continue;
+      *q = '\0';
+      
+      stpcpy(stpcpy(stpcpy(pathname, p), "/"), file);
+      
+      execve(pathname, argv, envp);
+      if (errno == EACCES)
+	eacces = 1;
+      else if (errno != ENOENT)
+	goto fail;
+    }
+  
+  free(path);
+  free(pathname);
+  return errno = (eaccess ? EACCES : ENOENT), -1;
+  
+ fail:
+  saved_errno = errno;
+  free(path_cwd);
+  if (len)
+    free(path_def);
+  free(path);
+  free(pathname);
+  errno = saved_errno;
+  return -1;
+}
+