================
@@ -2922,7 +2922,7 @@ static bool handleFloatFloatBinOp(EvalInfo &Info, const
BinaryOperator *E,
// If during the evaluation of an expression, the result is not
// mathematically defined [...], the behavior is undefined.
// FIXME: C++ rules require us to not conform to IEEE 754 here.
- if (LHS.isNaN()) {
+ if (!Info.getLangOpts().CPlusPlus23 && LHS.isNaN()) {
----------------
AaronBallman wrote:
The plot thickens, this may be a case where it's defined in C but C++ doesn't
bother defining much of anything about floating-point and thus it is UB:
https://github.com/cplusplus/draft/issues/5407
That said, https://eel.is/c++draft/basic.fundamental#12.sentence-8 seems to
make this implementation-defined and it would be reasonable for us to define
C++ as following the C semantics in situations where C++ is silent on the
behavior.
C is more clear on this point. C23 5.2.5.3.3p8: Floating types shall be able to
represent signed zeros or an unsigned zero and all normalized floating point
numbers. In addition, floating types may be able to contain other kinds of
floating-point numbers, such as subnormal floating-point numbers and
unnormalized floating-point numbers, and
values that are not floating-point numbers, such as NaNs and (signed and
unsigned) infinities.
https://github.com/llvm/llvm-project/pull/88978
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