fclose: restore errno after call to free() if close() fails

libs/libc/src/file.cpp

@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <fcntl.h>
 #include <luna.h>
 #include <stdio.h>
@@ -9,9 +10,15 @@ extern "C"
     int fclose(FILE* stream)
     {
         int status = close(stream->fd);
-        free(stream); // We do not want to leak memory. man fclose(3) says that whether fclose() fails or not, any
-                      // further operation on the stream results in undefined behavior. So we are free to free the
-                      // stream.
+        if (status < 0)
+        {
+            int savederr = errno;
+            free(stream); // We do not want to leak memory. man fclose(3) says that whether fclose() fails or not, any
+                          // further operation on the stream results in undefined behavior. So we are free to free the
+                          // stream.
+            errno = savederr; // free might reset errno. We don't want that.
+        }
+        else { free(stream); }
         return status;
     }