MaskRay marked 2 inline comments as done.
MaskRay added inline comments.
================
Comment at: clang/lib/Lex/PPMacroExpansion.cpp:1092
+ TT = *PP.getPreprocessorOpts().SourceDateEpoch;
+ TM = std::gmtime(&TT);
+ } else {
----------------
ychen wrote:
> MaskRay wrote:
> > ychen wrote:
> > > Why not use localtime as the else branch?
> > >
> > > As mentioned above, diagnose null TM here or when parsing the
> > > user-specifed value. A small trade-off to make, up to you.
> > Can you elaborate? With the check in Frontend I think a check here is not
> > necessary...
> Sorry I was not clear. The time_t value is not portable so it is hard to
> diagnose in a target-independent way. For example, `253402300799` is too big
> of a value for windows that `gmtime` returns null (causes crash at `asctime`
> in the similar case below). We could diagnose when gmtime/localtime returns
> null, which is portable.
I am still confused. In practice, a 64-bit `gmtime` implementation may returns
null when `tm_year` would overflow while 32-bit `gmtime` can't. The way (with a
more restricted upper bound) we check SOURCE_DATE_EPOCH in Frontend,
`std::gmtime(&TT);` cannot return null. `localtime(&TT)` for `time(nullptr)`
may overflow as where but that is an pre-existing issue.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D135045/new/
https://reviews.llvm.org/D135045
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