add stub for shm_open() and shm_unlink

  Untested and needs testsuite exercise added

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

librt/shm.c

@@ -0,0 +1,98 @@
+/* Copyright (C) 2009 Bernhard Reutner-Fischer <uclibc@uclibc.org>
+ *
+ * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+ */
+
+#include <features.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#ifndef O_CLOEXEC
+#include <errno.h>
+#endif
+
+#ifndef _PATH_SHM
+#define _PATH_SHM "/dev/shm/"
+#endif
+
+#ifndef NAME_MAX
+#define NAME_MAX 255
+#endif
+
+/* Get name of dummy shm operation handle.
+ * Returns a malloc'ed buffer containing the OS specific path
+ * to the shm filename or NULL upon failure.
+ */
+static __attribute_noinline__ char* get_shm_name(const char*name) __nonnull((1));
+static char* get_shm_name(const char*name)
+{
+	char *path;
+	int i;
+
+	/* Skip leading slashes */
+	while (*name == '/')
+		++name;
+#ifdef __USE_GNU
+	i = asprintf(&path, _PATH_SHM "%s", name);
+	if (i < 0)
+		return NULL;
+#else
+	path = malloc(NAME_MAX);
+	if (path == NULL)
+		return NULL;
+	i = snprintf(path, NAME_MAX, _PATH_SHM "%s", name);
+	if (i < 0) {
+		free(path);
+		return NULL;
+	}
+#endif
+	return path;
+}
+
+int shm_open(const char *name, int oflag, mode_t mode)
+{
+	int fd, old_errno;
+	char *shm_name = get_shm_name(name);
+
+	/* Stripped multiple '/' from start; may have set errno properly */
+	if (shm_name == NULL)
+		return -1;
+	/* The FD_CLOEXEC file descriptor flag associated with the new
+	 * file descriptor is set.  */
+#ifdef O_CLOEXEC
+	 /* Just open it with CLOEXEC set, for brevity */
+	fd = open(shm_name, oflag | O_CLOEXEC, mode);
+#else
+	fd = open(shm_name, oflag, mode);
+	if (fd >= 0) {
+		int fdflags = fcntl(fd, F_GETFD, 0);
+		if (fdflags >= 0)
+			fdflags = fcntl(fd, F_SETFD, fdflags | FD_CLOEXEC);
+		if (fdflags < 0) {
+			close(fd);
+			fd = -1;
+		}
+	}
+#endif
+	old_errno = errno;
+	free(shm_name);
+	errno = old_errno;
+	return fd;
+}
+
+int shm_unlink(const char *name)
+{
+	char *shm_name = get_shm_name(name);
+	int ret;
+
+	/* Stripped multiple '/' from start; may have set errno properly */
+	if (shm_name == NULL)
+		return -1;
+	ret = unlink(shm_name);
+	free(shm_name);
+	return ret;
+}