Win32: implement basic symlink() (file symlinks only)

Implement symlink() that always creates file symlinks. Fails with ENOSYS
if symlinks are disabled or the CreateSymbolicLinkW() API is missing.

Signed-off-by: Karsten Blees <[email protected]>

Author: kblees

compat/mingw.c

@@ -231,6 +231,9 @@ static int retry_ask_yes_no(int *tries, const char *format, ...)
 	return result;
 }
 
+
+DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateSymbolicLinkW, LPCWSTR, LPCWSTR, DWORD);
+
 /* Normalizes NT paths as returned by some low-level APIs. */
 static wchar_t *normalize_ntpath(wchar_t *wbuf)
 {
@@ -2009,6 +2012,34 @@ int link(const char *oldpath, const char *newpath)
 	return 0;
 }
 
+int symlink(const char *oldpath, const char *newpath)
+{
+	wchar_t woldpath[MAX_LONG_PATH], wnewpath[MAX_LONG_PATH];
+	int len;
+
+	/* fail if symlinks are disabled or API is not supported (WinXP) */
+	if (!has_symlinks || !INIT_PROC_ADDR(CreateSymbolicLinkW)) {
+		errno = ENOSYS;
+		return -1;
+	}
+
+	if ((len = xutftowcs_long_path(woldpath, oldpath)) < 0
+			|| xutftowcs_long_path(wnewpath, newpath) < 0)
+		return -1;
+
+	/* convert target dir separators to backslashes */
+	while (len--)
+		if (woldpath[len] == '/')
+			woldpath[len] = '\\';
+
+	/* create file symlink */
+	if (!CreateSymbolicLinkW(wnewpath, woldpath, 0)) {
+		errno = err_win_to_posix(GetLastError());
+		return -1;
+	}
+	return 0;
+}
+
 typedef struct _REPARSE_DATA_BUFFER {
 	DWORD  ReparseTag;
 	WORD   ReparseDataLength;

compat/mingw.h

@@ -93,8 +93,6 @@ struct itimerval {
  * trivial stubs
  */
 
-static inline int symlink(const char *oldpath, const char *newpath)
-{ errno = ENOSYS; return -1; }
 static inline int fchmod(int fildes, mode_t mode)
 { errno = ENOSYS; return -1; }
 #ifndef __MINGW64_VERSION_MAJOR
@@ -180,6 +178,7 @@ struct passwd *getpwuid(uid_t uid);
 int setitimer(int type, struct itimerval *in, struct itimerval *out);
 int sigaction(int sig, struct sigaction *in, struct sigaction *out);
 int link(const char *oldpath, const char *newpath);
+int symlink(const char *oldpath, const char *newpath);
 int readlink(const char *path, char *buf, size_t bufsiz);
 
 /*