https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97484
--- Comment #3 from Brecht Sanders <brechtsanders at users dot sourceforge.net> --- MinGW is pure C, so it doesn't use: using namespace std; But I do see Ninja doing this before including windows.h. However GCC 10 and older have no issue with this. What changed in GCC 11 to cause the issue?