[Bug libstdc++/121148] Should use modular arithmetic for _Atomic_word

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121148

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Ha yes, my patch uses -fwrapv, it's just a typo :)

--- a/libstdc++-v3/libsupc++/Makefile.am
+++ b/libstdc++-v3/libsupc++/Makefile.am
@@ -132,6 +132,11 @@ atomicity_file =
${glibcxx_srcdir}/$(ATOMICITY_SRCDIR)/atomicity.h
 atomicity.cc: ${atomicity_file}
        $(LN_S) ${atomicity_file} ./atomicity.cc || true

+atomicity.lo: atomicity.cc
+       $(LTCOMPILE) -fwrapv -c $<
+atomicity.o: atomicity.cc
+       $(CXXCOMPILE) -fwrapv -c $<
+
 if OS_IS_DARWIN
 # See PR 112397
 new_opvnt.lo: new_opvnt.cc