aaron.ballman added a comment. In D121122#3402334 <https://reviews.llvm.org/D121122#3402334>, @bjope wrote:
> Hello. We've got some problem in our downstream tests after this patch and > I'm trying to figure out how things are supposed to work. Maybe someone being > part of this review knows. Sorry for the troubles! > Problem is that we have some libc verification suites that include test cases > using `float_t`. But in math.h from for example newlib the type float_t isn't > defined if FLT_EVAL_METHOD is set to -1. > The standard says that float_t is implementation defined when FLT_EVAL_METHOD > isn't 0/1/2. But I'm not quite sure how that is supposed to be handled (such > as where to define float_t if not in math.h). The way I read the requirements in C2x 7.12p3 are that the types `float_t` and `double_t` are always defined in `<math.h>`, but in the event `FLT_EVAL_METHOD` isn't 0, 1, or 2, the implementation has to pick whatever type makes the most sense for the underlying types. > One question is: If I have a piece of C99 code using float_t, is that code > not allowed to be compiled using fast-math? The standard doesn't admit that fast math is a thing; it's up to the implementations to define what their fast math extension does. > I guess it should be seen as with fast-math the float_t precision is unknown. > But the type still has to be defined somewhere or else the frontend will > complain about "unknown type name". But I'm not sure where this is supposed > to be handled. I think it should still be handled in `<math.h>`. *I am not a C floating point expert, so take this suggestion with a grain of salt*: I think it is defensible to fallback to defining `float_t` as `float` and `double_t` as `double` when the eval method is indeterminable. @andrew.w.kaylor may have more nuanced thoughts here. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D121122/new/ https://reviews.llvm.org/D121122 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
