[PATCH] D103938: Diagnose -Wunused-value based on CFG reachability

[Nico Weber via Phabricator via cfe-commits]

thakis added a comment.

This flags this code from absl:

  template <typename ValueT, typename GenT,
            typename std::enable_if<std::is_integral<ValueT>::value, int>::type =
                (GenT{}, 0)>
  constexpr FlagDefaultArg DefaultArg(int) {
    return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kOneWord};
  }

(https://source.chromium.org/chromium/chromium/src/+/main:third_party/abseil-cpp/absl/flags/internal/flag.h;l=293?q=third_party%2Fabseil-cpp%2Fabsl%2Fflags%2Finternal%2Fflag.h)

  ../../third_party/abseil-cpp/absl/flags/internal/flag.h:293:16: warning: left operand of comma operator has no effect [-Wunused-value]
                (GenT{}, 0)>
                 ^   ~~
  ../../third_party/abseil-cpp/absl/flags/internal/flag.h:293:16: warning: left operand of comma operator has no effect [-Wunused-value]
                (GenT{}, 0)>
                 ^   ~~

I guess it has a SFINAE effect there?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D103938/new/

https://reviews.llvm.org/D103938