unix: make OpenBSD uv_exepath work

some users of libuv rely on uv_exepath to be an actual path to a
program. unfortunately, the OpenBSD KERN_PROC_ARGV sysctl just returns
what is in argv[0], so if the program was executed by being looked up in
$PATH, uv_exepath would only return the basename and not an actual path.

to fix, this use the same approach as IBM i, OS/390 and AIX by searching
with uv__search_path. this is also the same approach the Zig language
has taken for the similar selfExePath function for OpenBSD.

the tests expect that uv_exepath still works after uv_set_process_title,
which on BSD is a call to setproctitle. the place setproctitle stores to
is the same place that KERN_PROC_ARGV reads from, so we need to stash
the original argv[0] in uv_setup_args to recover it later in uv_exepath.

src/unix/bsd-proctitle.c

@@ -29,7 +29,7 @@
 static uv_mutex_t process_title_mutex;
 static uv_once_t process_title_mutex_once = UV_ONCE_INIT;
 static char* process_title;
-
+char* uv_saved_argv0;
 
 static void init_process_title_mutex_once(void) {
   if (uv_mutex_init(&process_title_mutex))
@@ -45,6 +45,7 @@ void uv__process_title_cleanup(void) {
 
 char** uv_setup_args(int argc, char** argv) {
   process_title = argc > 0 ? uv__strdup(argv[0]) : NULL;
+  uv_saved_argv0 = argc > 0 ? uv__strdup(argv[0]) : NULL;
   return argv;
 }
 

src/unix/internal.h

@@ -591,4 +591,6 @@ int uv__get_constrained_cpu(long long* quota);
 #define UV__KQUEUE_EVFILT_USER 0
 #endif
 
+extern char* uv_saved_argv0;
+
 #endif /* UV_UNIX_INTERNAL_H_ */

src/unix/openbsd.c

@@ -59,54 +59,13 @@ void uv_loadavg(double avg[3]) {
 
 
 int uv_exepath(char* buffer, size_t* size) {
-  int mib[4];
-  char **argsbuf = NULL;
-  size_t argsbuf_size = 100U;
-  size_t exepath_size;
-  pid_t mypid;
-  int err;
-
   if (buffer == NULL || size == NULL || *size == 0)
     return UV_EINVAL;
 
-  mypid = getpid();
-  for (;;) {
-    err = UV_ENOMEM;
-    argsbuf = uv__reallocf(argsbuf, argsbuf_size);
-    if (argsbuf == NULL)
-      goto out;
-    mib[0] = CTL_KERN;
-    mib[1] = KERN_PROC_ARGS;
-    mib[2] = mypid;
-    mib[3] = KERN_PROC_ARGV;
-    if (sysctl(mib, ARRAY_SIZE(mib), argsbuf, &argsbuf_size, NULL, 0) == 0) {
-      break;
-    }
-    if (errno != ENOMEM) {
-      err = UV__ERR(errno);
-      goto out;
-    }
-    argsbuf_size *= 2U;
-  }
+  if (uv_saved_argv0 == NULL)
+    return UV_EINVAL;
 
-  if (argsbuf[0] == NULL) {
-    err = UV_EINVAL;  /* FIXME(bnoordhuis) More appropriate error. */
-    goto out;
-  }
-
-  *size -= 1;
-  exepath_size = strlen(argsbuf[0]);
-  if (*size > exepath_size)
-    *size = exepath_size;
-
-  memcpy(buffer, argsbuf[0], *size);
-  buffer[*size] = '\0';
-  err = 0;
-
-out:
-  uv__free(argsbuf);
-
-  return err;
+  return uv__search_path(uv_saved_argv0, buffer, size);
 }
 
 

test/test-get-currentexe.c

@@ -35,9 +35,6 @@ TEST_IMPL(get_currentexe) {
 #if defined(__QEMU__)
   RETURN_SKIP("Test does not currently work in QEMU");
 #endif
-#if defined(__OpenBSD__)
-  RETURN_SKIP("Test does not currently work in OpenBSD");
-#endif
 
   char buffer[PATHMAX];
   char path[PATHMAX];