Fix msvc unreachable code warnings#1841
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@CaseyCarter , any steps I can take to help advance this PR? |
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Fixes #1762 and fixes #1814 .
MSVC's
__assume(false)results in4702: unreachable codewarnings when used as as the first expression in a comma-sequenced return statement (as invariant_visit_'sreturn (RANGES_EXPECT(false), 0);.This PR adds a
RANGES_EXPECT_UNREACHABLE_RETURN(RETURN_VALUE)macro to be used in these cases, which expands to solely the__assume(false);in MSVC release builds; otherwise expands to the priorreturn (RANGES_EXPECT(false), RETURN_VALUE);value.note: gcc no longer implements
-Wunreachable-codeand clang can produce unreachable code warnings, but not in the case ofRANGES_ASSUME()'s conditional use of__builtin_unreachable(). Both compilers still require that areturnoperation be present afterRANGES_ASSUME(false)'s invocation of their__builtin_unreachable()intrinsic.