Add absolutepath helper for paths that may not exist

os/mingw.c

@@ -2408,6 +2408,40 @@ char* windows_realpath(const char* path, char* resolved_path)
 /****************************************************************************/
 /* fs */
 
+char* absolutepath(const char* restrict path, char* restrict resolved_path)
+{
+	if (path == 0 || path[0] == 0 || resolved_path == 0) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	wchar_t wpath[CONV_MAX];
+	wchar_t wfull[CONV_MAX];
+
+	if (!u8tou16_mayfail(wpath, CONV_MAX, path, strlen(path) + 1, 0)) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	DWORD len = GetFullPathNameW(wpath, CONV_MAX, wfull, 0);
+	if (len == 0) {
+		windows_errno(GetLastError());
+		return 0;
+	}
+
+	if (len >= CONV_MAX) {
+		errno = ENAMETOOLONG;
+		return 0;
+	}
+
+	if (!u16tou8_mayfail(resolved_path, CONV_MAX, wfull, len + 1, 0)) {
+		errno = ENAMETOOLONG;
+		return 0;
+	}
+
+	return resolved_path;
+}
+
 static BOOL GetFilePhysicalOffset(HANDLE h, uint64_t* physical)
 {
 	STARTING_VCN_INPUT_BUFFER svib;

os/os.h

@@ -273,6 +273,18 @@ int os_validate_exec_input(const char* str);
 /****************************************************************************/
 /* fs */
 
+/**
+ * Make a pathname absolute using the current working directory.
+ *
+ * The pathname is not required to exist and symbolic links are not resolved.
+ * The resolved_path buffer must be at least PATH_MAX bytes and must not overlap path.
+ *
+ * \param path Input pathname.
+ * \param resolved_path Destination buffer.
+ * \return resolved_path on success, 0 on failure with errno set.
+ */
+char* absolutepath(const char* restrict path, char* restrict resolved_path);
+
 /**
  * Invalid inode number.
  *

os/unix.c

@@ -122,6 +122,42 @@ const char* os_signal_name(int sig)
 /****************************************************************************/
 /* fs */
 
+char* absolutepath(const char* restrict path, char* restrict resolved_path)
+{
+	if (path == 0 || path[0] == 0 || resolved_path == 0) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	size_t path_len = strlen(path);
+	if (path_len >= PATH_MAX) {
+		errno = ENAMETOOLONG;
+		return 0;
+	}
+
+	if (path[0] == '/') {
+		memcpy(resolved_path, path, path_len + 1);
+		return resolved_path;
+	}
+
+	if (getcwd(resolved_path, PATH_MAX) == 0)
+		return 0;
+
+	size_t resolved_len = strlen(resolved_path);
+	int separator = resolved_len != 0 && resolved_path[resolved_len - 1] != '/';
+
+	if (resolved_len + separator + path_len + 1 > PATH_MAX) {
+		errno = ENAMETOOLONG;
+		return 0;
+	}
+
+	if (separator)
+		resolved_path[resolved_len++] = '/';
+	memcpy(resolved_path + resolved_len, path, path_len + 1);
+
+	return resolved_path;
+}
+
 #if !HAVE_EACCESS
 int eaccess(const char* pathname, int mode)
 {