tryfix abspath c func with "" on windows

Author: IanButterworth

src/init.c

@@ -575,16 +575,33 @@ static char *abspath(const char *in, int nprefix)
         }
     }
 #else
-    DWORD n = GetFullPathName(in + nprefix, 0, NULL, NULL);
-    if (n <= 0) {
-        jl_error("fatal error: jl_options.image_file path too long or GetFullPathName failed");
+    // GetFullPathName intentionally errors if given an empty string so manually insert cwd
+    if (strlen(in) - nprefix == 0) {
+        size_t sz = strlen(in + nprefix) + 1;
+        size_t path_size = JL_PATH_MAX;
+        char *path = (char*)malloc_s(JL_PATH_MAX);
+        if (uv_cwd(path, &path_size)) {
+            jl_error("fatal error: unexpected error while retrieving current working directory");
+        }
+        char *out = (char*)malloc_s(path_size + 1 + sz + nprefix);
+        memcpy(out, in, nprefix);
+        memcpy(out + nprefix, path, path_size);
+        out[nprefix + path_size] = PATHSEPSTRING[0];
+        memcpy(out + nprefix + path_size + 1, in + nprefix, sz);
+        free(path);
     }
-    char *out = (char*)malloc_s(n + nprefix);
-    DWORD m = GetFullPathName(in + nprefix, n, out + nprefix, NULL);
-    if (n != m + 1) {
-        jl_error("fatal error: jl_options.image_file path too long or GetFullPathName failed");
+    else {
+        DWORD n = GetFullPathName(in + nprefix, 0, NULL, NULL);
+        if (n <= 0) {
+            jl_error("fatal error: jl_options.image_file path too long or GetFullPathName failed");
+        }
+        char *out = (char*)malloc_s(n + nprefix);
+        DWORD m = GetFullPathName(in + nprefix, n, out + nprefix, NULL);
+        if (n != m + 1) {
+            jl_error("fatal error: jl_options.image_file path too long or GetFullPathName failed");
+        }
+        memcpy(out, in, nprefix);
     }
-    memcpy(out, in, nprefix);
 #endif
     return out;
 }