ebevhan marked an inline comment as done. ebevhan added inline comments.
================ Comment at: test/Sema/format-strings-bitfield-promotion.c:1 +// RUN: %clang_cc1 -triple x86_64-unknown-unknown -fsyntax-only -verify %s + ---------------- ebevhan wrote: > aaron.ballman wrote: > > aaron.ballman wrote: > > > Running your test through GCC looks like the behavior matches here for C; > > > can you also add a C++ test that demonstrates the behavior does not > > > change? > > > > > > https://godbolt.org/z/zRYDMG > > Strangely, the above godbolt link dropped the output windows, here's a > > different link that shows the behavioral differences between C and C++ mode > > in GCC: https://godbolt.org/z/R3zRHe > Hmm, I'll have a look at this. That gcc godbolt is a bit odd. The type of the bitfield expression in the C++ example is `long` and not `int`, but in Clang, it's clearly being converted. If I change the example a bit, we get this warning: ``` <source>:11:12: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=] 11 | printf("%d", bf.a); // expected-warning {{format specifies type 'long' but the argument has type 'int'}} | ~^ ~~~~ | | | | int long int ``` But in Clang, we get a cast to `int`: ``` | `-ImplicitCastExpr 0xd190748 <col:17, col:20> 'int' <IntegralCast> | `-ImplicitCastExpr 0xd190730 <col:17, col:20> 'long' <LValueToRValue> | `-MemberExpr 0xd190618 <col:17, col:20> 'long' lvalue bitfield .a 0xd18f790 | `-DeclRefExpr 0xd1905f8 <col:17> 'struct bitfields':'bitfields' lvalue Var 0xd18fa18 'bf' 'struct bitfields':'bitfields' ``` So gcc and Clang are doing things differently here. The code in `isPromotableBitField` says: ``` // FIXME: C does not permit promotion of a 'long : 3' bitfield to int. // We perform that promotion here to match GCC and C++. ``` but clearly gcc isn't doing this in the C++ case. The comments also mention some things about gcc bugs that Clang does not follow, but that's in reference to a C DR. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D51211/new/ https://reviews.llvm.org/D51211 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
