In Xcode, I want to find out the value of the STDC FP_CONTRACT pragma after including just float.h and math.h. To my surprise, I couldn't find any way to do it!
So the question: Am I just missing something here, or is there actually no way to verify how a #pragma has been set? Of course, I can force it to be set any way I want, but it's not quite the same.
Adding an answer since it was answered in comments:
There is absolutely no way to check at compile time how a pragma has been set. The exception would be if there are settings with predictable and identifiable effects, if you can verify the effect.
That’s not really possible with FP_CONTRACT because it allows contracting operations but doesn’t force it, so you can check the result of a*b+c but it may be contracted or not with FP_CONTRACT in effect.
#ifor `#if(n)def, there is nothing you can do.FP_CONTRACTspecifically, the default for whether FP expression contraction is enabled is implementation defined, so you should find it in your implementation's docs. However, the expected usage is that you issue that pragma when you actually care, and otherwise let the compiler do its thing as it chooses. Plus, you can limit the scope of that pragma if necessary, so that you don't need to affirmatively cancel its effects.