zahiraam added inline comments.
================
Comment at: clang/lib/Frontend/FrontendAction.cpp:845-855
+ if (Input.isFile() && Input.getFile() == "-") {
+ Preprocessor &PP = CI.getPreprocessor();
+ std::string PredefineBuffer;
+ PredefineBuffer.reserve(4080);
+ llvm::raw_string_ostream Predefines(PredefineBuffer);
+ Predefines << PP.getPredefines();
+ MacroBuilder Builder(Predefines);
----------------
aaron.ballman wrote:
> zahiraam wrote:
> > aaron.ballman wrote:
> > > I'm confused as to why we want to predefine this macro *only* when the
> > > input source is stdin? So I'm not certain I understand why this change is
> > > desired.
> > >
> > > e.g., https://godbolt.org/z/E8Y67381r (note how there's no
> > > `__FLT_EVAL_METHOD__` defined there)
> > I was offering a solution to the issue raised by @glandium in
> > https://reviews.llvm.org/D109239. I thought that the issue was only when
> > the source is stdin, but obviously not. The default setting should happen
> > under no condition.
> There have been a lot of reviews over this stuff, so I may be remembering
> incorrectly... but I thought it was a conscious decision to *not* predefine
> `__FLT_EVAL_METHOD__` because that value changes depending on pragmas in the
> TU. I thought the way that macro worked was that we registered it as a macro
> and we figure out its value at expansion time.
>
> (The original report confused me into thinking that `__FLT_EVAL_METHOD__` was
> behaving as though it was never defined, so expansion would never result in a
> correct value except when the eval method is `0`.)
Yes, you are remembering correctly. I looked at older comments and it's
something that was intended. We didn't want to pre-define it, until it is set
at expansion.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124004/new/
https://reviews.llvm.org/D124004
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