[clang] [RFC][C++20][Modules] Relax ODR check in unnamed modules (PR #111160)

[Chuanqi Xu via cfe-commits]

================
@@ -0,0 +1,32 @@
+// RUN: rm -fR %t
+// RUN: split-file %s %t
+// RUN: cd %t
+// RUN: %clang_cc1 -verify -std=c++20 -fskip-odr-check-in-gmf -emit-header-unit -xc++-user-header bz0.h
+// RUN: %clang_cc1 -verify -std=c++20 -fskip-odr-check-in-gmf -emit-header-unit -xc++-user-header bz1.h
+// RUN: %clang_cc1 -verify -std=c++20 -fskip-odr-check-in-gmf -emit-header-unit -xc++-user-header -fmodule-file=bz0.pcm -fmodule-file=bz1.pcm bz.cpp
+
+//--- compare
+template<typename _Tp>
+inline constexpr unsigned __cmp_cat_id = 1;
+
+template<typename... _Ts>
+constexpr auto __common_cmp_cat() {
+  (__cmp_cat_id<_Ts> | ...);
+}
+
+//--- bz0.h
+template <class T>
+int operator|(T, T);
+
+#include "compare"
----------------
ChuanqiXu9 wrote:

But this case, I feel this is a real ODR violation. The intention of skipping ODR checks in GMF is we have too many false positive ODR violation diagnostics. But I prefer to not make it for real ODR violations.

https://github.com/llvm/llvm-project/pull/111160