librb: add rb_path_to_self(), which provides fairly reliable runtime path detection

librb/configure.ac

@@ -211,8 +211,9 @@ AC_CHECK_TYPE([sa_family_t], [],
 
 
 dnl check for various functions...
-AC_CHECK_FUNCS([snprintf vsnprintf socketpair gettimeofday writev sendmsg gmtime_r strtok_r usleep posix_spawn strlcpy strlcat strnlen fstat signalfd select poll kevent port_create epoll_ctl arc4random getrusage timerfd_create])	
+AC_CHECK_FUNCS([snprintf vsnprintf socketpair gettimeofday writev sendmsg gmtime_r strtok_r usleep posix_spawn getexecname strlcpy strlcat strnlen fstat signalfd select poll kevent port_create epoll_ctl arc4random getrusage timerfd_create])	
 
+AC_SEARCH_LIBS(dlinfo, dl, AC_DEFINE(HAVE_DLINFO, 1, [Define if you have dlinfo]))
 AC_SEARCH_LIBS(nanosleep, rt posix4, AC_DEFINE(HAVE_NANOSLEEP, 1, [Define if you have nanosleep]))
 AC_SEARCH_LIBS(timer_create, rt, AC_DEFINE(HAVE_TIMER_CREATE, 1, [Define if you have timer_create]))
 RB_CHECK_TIMER_CREATE

librb/include/rb_tools.h

@@ -371,5 +371,6 @@ void rb_zstring_append_from_c(rb_zstring_t *zs, const char *buf, size_t len);
 char *rb_zstring_to_c(rb_zstring_t *zs, char *buf, size_t len);
 char *rb_zstring_to_c_alloc(rb_zstring_t *zs);
 size_t rb_zstring_to_ptr(rb_zstring_t *zs, void **ptr);
+const char *rb_path_to_self(void);
 
 #endif /* __TOOLS_H__ */

librb/src/export-syms.txt

@@ -188,3 +188,4 @@ rb_zstring_serialized
 rb_zstring_to_c
 rb_zstring_to_c_alloc
 rb_zstring_to_ptr
+rb_path_to_self

librb/src/unix.c

@@ -26,19 +26,23 @@
 #include <librb_config.h>
 #include <rb_lib.h>
 
-
 #ifndef _WIN32
 
 #include <sys/wait.h>
 
+#ifdef HAVE_DLINFO
+# include <link.h>
+# include <dlfcn.h>
+#endif
+
+#ifdef __APPLE__
+#include <mach-o/dyld.h>
+#include <crt_externs.h>
+#endif
 
 #if defined(HAVE_SPAWN_H) && defined(HAVE_POSIX_SPAWN)
 #include <spawn.h>
 
-#ifdef __APPLE__
-#include <crt_externs.h>
-#endif
-
 #ifndef __APPLE__
 extern char **environ;
 #endif
@@ -151,5 +155,36 @@ rb_getpid(void)
 	return getpid();
 }
 
+const char *
+rb_path_to_self(void)
+{
+	static char path_buf[4096];
+#if defined(HAVE_GETEXECNAME)
+	char *s = getexecname();
+	if (s == NULL)
+		return NULL;
+	realpath(s, path_buf);
+	return path_buf;
+#elif defined(HAVE_DLINFO)
+	struct link_map *map = NULL;
+	dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &map);
+	if (map == NULL)
+		return NULL;
+	realpath(map->l_name, path_buf);
+#elif defined(__linux__)
+	if (readlink("/proc/self/exe", path_buf, sizeof path_buf) != -1)
+		return path_buf;
+	return NULL;
+#elif defined(__APPLE__)
+	char tmp_path[4096];
+	uint32_t pathlen = 4096;
+
+	if (_NSGetExecutablePath(tmp_path, &pathlen) < 0)
+		return NULL;
+
+	realpath(tmp_path, path_buf);
+	return path_buf;
+#endif
+}
 
 #endif /* !WIN32 */

librb/src/win32.c

@@ -614,6 +614,15 @@ rb_strerror(int error)
 	rb_strlcpy(buf, _rb_strerror(error), sizeof(buf));
 	return buf;
 }
+
+const char *
+rb_path_to_self(void)
+{
+	static char path_buf[MAX_PATH];
+	GetModuleFileName(NULL, exepath, MAX_PATH);
+	return path_buf;
+}
+
 #else /* win32 not supported */
 int
 rb_init_netio_win32(void)