aaron.ballman 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);
----------------
zahiraam wrote:
> 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.
Thank you for double-checking! I would recommend that you abandon this change,
and instead make an NFC change to
https://clang.llvm.org/docs/UsersManual.html#a-note-about-flt-eval-method to
make it clear that this macro does not appear when dumping preprocessor macro
definitions but is instead resolved when expanding it as a macro definition.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124004/new/
https://reviews.llvm.org/D124004
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