win32: dirent: handle errors

Previously all error conditions were ignored. Be nice, and set errno
when we should.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.c

@@ -1582,7 +1582,7 @@ struct dirent *mingw_readdir(DIR *dir)
 	HANDLE handle;
 	struct mingw_DIR *mdir = (struct mingw_DIR*)dir;
 
-	if (!dir->dd_handle) {
+	if (!dir || !dir->dd_handle) {
 		errno = EBADF; /* No set_errno for mingw */
 		return NULL;
 	}

compat/msvc.c

@@ -5,8 +5,29 @@
 
 DIR *opendir(const char *name)
 {
-	int len = strlen(name);
+	DWORD attrs = GetFileAttributes(name);
+	int len;
 	DIR *p;
+
+	/* check for valid path */
+	if (attrs == INVALID_FILE_ATTRIBUTES) {
+		errno = ENOENT;
+		return NULL;
+	}
+
+	/* check if it's a directory */
+	if (!(attrs & FILE_ATTRIBUTE_DIRECTORY)) {
+		errno = ENOTDIR;
+		return NULL;
+	}
+
+	/* check that the pattern won't be too long for FindFirstFileA */
+	len = strlen(name);
+	if (len + 2 >= MAX_PATH) {
+		errno = ENAMETOOLONG;
+		return NULL;
+	}
+
 	p = malloc(sizeof(DIR) + len + 2);
 	if (!p)
 		return NULL;
@@ -21,6 +42,11 @@ DIR *opendir(const char *name)
 }
 int closedir(DIR *dir)
 {
+	if (!dir) {
+		errno = EBADF;
+		return -1;
+	}
+
 	if (dir->dd_handle != (long)INVALID_HANDLE_VALUE)
 		FindClose((HANDLE)dir->dd_handle);
 	free(dir);