mingw: Add implementation of realpath()

The mingw port used _fullpath() until now, but the behaviour is not exactly
the same as realpath()'s on unix; major difference being that it doesn't
return an error for non-existing files, which would bypass main's error
checking and bail out without any error message.

Also realpath() will return forward slashes only since main() relies on that.

1 files changed, 42 insertions, 0 deletions

diff --git a/windows/realpath.c b/windows/realpath.c
new file mode 100644
index 0000000000..550298a7d5
--- /dev/null
+++ b/windows/realpath.c
@@ -0,0 +1,42 @@
+#include <stdlib.h>
+#include <errno.h>
+#include <io.h>
+
+#ifndef R_OK
+    #define R_OK 4
+#endif
+
+// Make sure a path only has forward slashes.
+char *to_unix_path(char *p) {
+    if (p != NULL) {
+        char *pp = p;
+        while (*pp != 0) {
+            if (*pp == '\\')
+                *pp = '/';
+            ++pp;
+        }
+    }
+    return p;
+}
+
+// Implement realpath() using _fullpath and make it use the same error codes as realpath() on unix.
+// Also have it return a path with forward slashes only as some code relies on this,
+// but _fullpath() returns backward slashes no matter what.
+char *realpath(const char *path, char *resolved_path) {
+    char *ret = NULL;
+    if (path == NULL) {
+        errno = EINVAL;
+    } else if (access(path, R_OK) == 0) {
+        ret = resolved_path;
+        if (ret == NULL)
+            ret = malloc(_MAX_PATH);
+        if (ret == NULL) {
+            errno = ENOMEM;
+        } else {
+            ret = _fullpath(ret, path, _MAX_PATH);
+            if (ret == NULL)
+                errno = EIO;
+        }
+    }
+    return to_unix_path(ret);
+}