[PATCH] D83211: Factor out call to EXTRACTOR in generateCC1CommandLine

[Duncan P. N. Exon Smith via Phabricator via cfe-commits]

dexonsmith added inline comments.


================
Comment at: clang/lib/Frontend/CompilerInvocation.cpp:3938
+  if ((FLAGS)&options::CC1Option) {                                            \
+    const auto &Extracted = EXTRACTOR(this->KEYPATH);                          \
+    if (ALWAYS_EMIT || Extracted != DEFAULT_VALUE)                             \
----------------
dexonsmith wrote:
> jansvoboda11 wrote:
> > Bigcheese wrote:
> > > Will this ever have an issue with lifetime? I can see various values for `EXTRACTOR` causing issues here. https://abseil.io/tips/107
> > > 
> > > 
> > > It would be good to at least document somewhere the restrictions on `EXTRACTOR`.
> > Mentioned the reference lifetime extension in a comment near extractor definitions.
> It might be safer to refactor as:
> ```
> // Capture the extracted value as a lambda argument to avoid potential
> // lifetime extension issues.
> [&](const auto &Extracted) {
>   if (ALWAYS_EMIT || Extracted != (DEFAULT_VALUE))
>     DENORMALIZER(Args, SPELLING, SA, TABLE_INDEX, Extracted);
> }(EXTRACTOR(this->KEYPATH));
> ```
> 
Might be even better to avoid the generic lambda:
```
// Capture the extracted value as a lambda argument to avoid potential
// lifetime extension issues.
using ExtractedType =
    std::remove_const_t<std::remove_reference_t<
        decltype(EXTRACTOR(this->KEYPATH))>>
[&](const ExtractedType &Extracted) {
  if (ALWAYS_EMIT || Extracted != (DEFAULT_VALUE))
    DENORMALIZER(Args, SPELLING, SA, TABLE_INDEX, Extracted);
}(EXTRACTOR(this->KEYPATH));
```
(since generic vs. non-generic could affect compile-time of CompilerInvocation.cpp given how many instances there will be).


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D83211/new/

https://reviews.llvm.org/D83211