================ @@ -457,6 +457,28 @@ Note that **currently** the compiler doesn't consider inconsistent macro definit Currently Clang would accept the above example. But it may produce surprising results if the debugging code depends on consistent use of ``NDEBUG`` also in other translation units. +Definitions consistency +^^^^^^^^^^^^^^^^^^^^^^^ + +The C++ language defines that same declarations in different translation units should have +the same definition, as known as ODR (One Definition Rule). Prior to modules, the translation +units don't dependent on each other and the compiler itself don't and can't perform a strong +ODR violation check. Sometimes it is the linker does some jobs related to ODR, where the +higher level semantics are missing. With the introduction of modules, now the compiler have +the chance to perform ODR violations with language semantics across translation units. + +However, in the practice we found the existing ODR checking mechanism may be too aggressive. +In the many issue reports about ODR violation diagnostics, most of them are false positive +ODR violations and the true positive ODR violations are rarely reported. Also MSVC don't +perform ODR check for declarations in the global module fragment. + +So in order to get better user experience, save the time checking ODR and keep consistent +behavior with MSVC, we disabled the ODR check for the declarations in the global module +fragment by default. Users who want more strict check can still use the +``-Xclang -fno-skip-odr-check-in-gmf`` flag to get the ODR check enabled. It is also +encouraged to report issues if users find false positive ODR violations or false negative ODR +violations with the flag enabled. ---------------- mizvekov wrote:
Again I find this paragraph concerning 3). This jusitifies in terms of MSVC conformance, but doesn't limit the behavior to that environment. Also I don't think we offer compiler switches that decrease standards conformance in order to save build time. https://github.com/llvm/llvm-project/pull/79959 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
