[PATCH] D87528: Enable '#pragma STDC FENV_ACCESS' in frontend cf. D69272 - Work in Progress

[Melanie Blower via Phabricator via cfe-commits]

mibintc added a comment.

In D88498 <https://reviews.llvm.org/D88498> @rsmith wrote,
s far from clear to me that this is correct in C++. In principle, for a dynamic initializer, the rounding mode could have been set by an earlier initializer.

Perhaps we can make an argument that, due to the permission to interleave initializers from different TUs, every dynamic initializer must leave the program in the default rounding mode, but I don't think even that makes this approach correct, because an initializer could do this:

double d;
double e = (fesetround(...), d = some calculation, fesetround(...default...), d);
I think we can only do this in C and will need something different for C++.

(I think this also has problems in C++ due to constexpr functions: it's not the case that all floating point operations that will be evaluated as part of the initializer lexically appear within it.)

For the initialization expression to be correct, the RoundingMode at the declaration of e needs to be set to Dynamic, right?


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