[C++20] [Modules] Introduce -fskip-odr-check-in-gmf #79959
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@@ -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. | ||
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| Definitions consistency | ||
| ^^^^^^^^^^^^^^^^^^^^^^^ | ||
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| 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. | ||
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| 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. | ||
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| 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. | ||
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| ABI Impacts | ||
| ----------- | ||
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| // RUN: %clang -std=c++20 -### -c %s 2>&1 | FileCheck %s | ||
| // RUN: %clang -std=c++20 -fno-skip-odr-check-in-gmf -### -c %s 2>&1 \ | ||
| // RUN: | FileCheck %s --check-prefix=UNUSED | ||
| // RUN: %clang -std=c++20 -Xclang -fno-skip-odr-check-in-gmf -### -c %s 2>&1 \ | ||
| // RUN: | FileCheck %s --check-prefix=NO-SKIP | ||
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| // CHECK: -fskip-odr-check-in-gmf | ||
| // UNUSED: warning: argument unused during compilation: '-fno-skip-odr-check-in-gmf' | ||
| // UNUSED-NOT: -fno-skip-odr-check-in-gmf | ||
| // NO-SKIP: -fskip-odr-check-in-gmf{{.*}}-fno-skip-odr-check-in-gmf |
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@@ -5,6 +5,12 @@ | |
| // RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-module-interface -o %t/A.pcm | ||
| // RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t -I%t -DDIFFERENT %t/B.cppm -verify | ||
| // RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t -I%t %t/B.cppm -verify | ||
| // | ||
| // Testing the behavior of `-fskip-odr-check-in-gmf` | ||
| // RUN: %clang_cc1 -std=c++20 -fskip-odr-check-in-gmf %t/A.cppm -emit-module-interface -o %t/A.pcm | ||
| // RUN: %clang_cc1 -std=c++20 -fskip-odr-check-in-gmf -fprebuilt-module-path=%t -I%t \ | ||
| // RUN: -DDIFFERENT -DSKIP_ODR_CHECK_IN_GMF %t/B.cppm -verify | ||
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| //--- foo.h | ||
| #ifndef FOO_H | ||
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@@ -70,6 +76,16 @@ module; | |
| export module B; | ||
| import A; | ||
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| #ifdef SKIP_ODR_CHECK_IN_GMF | ||
| // [email protected]:* {{call to object of type '__fn' is ambiguous}} | ||
| // expected-note@* 1+{{candidate function}} | ||
| #elif defined(DIFFERENT) | ||
| // [email protected]:41 {{'__fn::operator()' from module 'A.<global>' is not present in definition of '__fn' provided earlier}} | ||
| // expected-note@* 1+{{declaration of 'operator()' does not match}} | ||
| #else | ||
| // expected-no-diagnostics | ||
| #endif | ||
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| template <class T> | ||
| struct U { | ||
| auto operator+(U) { return 0; } | ||
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@@ -87,10 +103,3 @@ void foo() { | |
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| __fn{}(U<int>(), U<int>()); | ||
| } | ||
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@@ -10,6 +10,12 @@ | |
| // RUN: %clang_cc1 -std=c++20 %t/mod4.cppm -fmodule-file=mod3=%t/mod3.pcm \ | ||
| // RUN: -fsyntax-only -verify | ||
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| // Testing the behavior of `-fskip-odr-check-in-gmf` | ||
| // RUN: %clang_cc1 -std=c++20 %t/mod3.cppm -fskip-odr-check-in-gmf \ | ||
| // RUN: -emit-module-interface -o %t/mod3.pcm | ||
| // RUN: %clang_cc1 -std=c++20 %t/mod4.cppm -fmodule-file=mod3=%t/mod3.pcm \ | ||
| // RUN: -fskip-odr-check-in-gmf -DSKIP_ODR_CHECK_IN_GMF -fsyntax-only -verify | ||
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| //--- size_t.h | ||
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| extern "C" { | ||
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@@ -57,13 +63,17 @@ export module mod3; | |
| export using std::align_val_t; | ||
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| //--- mod4.cppm | ||
| module; | ||
| #include "signed_size_t.h" | ||
| #include "csize_t" | ||
| #include "align.h" | ||
| export module mod4; | ||
| import mod3; | ||
| export using std::align_val_t; | ||
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| #ifdef SKIP_ODR_CHECK_IN_GMF | ||
| // expected-no-diagnostics | ||
| #else | ||
| // [email protected]:* {{'std::align_val_t' has different definitions in different modules; defined here first difference is enum with specified type 'size_t' (aka 'int')}} | ||
| // [email protected]:* {{but in 'mod3.<global>' found enum with specified type 'size_t' (aka 'unsigned int')}} | ||
| #endif | ||
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| @@ -0,0 +1,56 @@ | ||
| // RUN: rm -rf %t | ||
| // RUN: mkdir -p %t | ||
| // RUN: split-file %s %t | ||
| // | ||
| // Baseline testing to make sure we can detect the ODR violation from the CC1 invocation. | ||
| // RUNX: %clang_cc1 -std=c++20 %t/a.cppm -emit-module-interface -o %t/a.pcm | ||
| // RUNX: %clang_cc1 -std=c++20 %t/b.cppm -emit-module-interface -o %t/b.pcm | ||
| // RUNX: %clang_cc1 -std=c++20 %t/test.cc -fprebuilt-module-path=%t -fsyntax-only -verify | ||
| // | ||
| // Testing that we can ignore the ODR violation from the driver invocation. | ||
| // RUN: %clang -std=c++20 %t/a.cppm --precompile -o %t/a.pcm | ||
| // RUN: %clang -std=c++20 %t/b.cppm --precompile -o %t/b.pcm | ||
| // RUN: %clang -std=c++20 %t/test.cc -fprebuilt-module-path=%t -fsyntax-only -Xclang -verify \ | ||
| // RUN: -DIGNORE_ODR_VIOLATION | ||
| // | ||
| // Testing that the driver can require to check the ODR violation. | ||
| // RUN: %clang -std=c++20 -Xclang -fno-skip-odr-check-in-gmf %t/a.cppm --precompile -o %t/a.pcm | ||
| // RUN: %clang -std=c++20 -Xclang -fno-skip-odr-check-in-gmf %t/b.cppm --precompile -o %t/b.pcm | ||
| // RUN: %clang -std=c++20 -Xclang -fno-skip-odr-check-in-gmf %t/test.cc -fprebuilt-module-path=%t \ | ||
| // RUN: -fsyntax-only -Xclang -verify | ||
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| //--- func1.h | ||
| bool func(int x, int y) { | ||
| return true; | ||
| } | ||
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| //--- func2.h | ||
| bool func(int x, int y) { | ||
| return false; | ||
| } | ||
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| //--- a.cppm | ||
| module; | ||
| #include "func1.h" | ||
| export module a; | ||
| export using ::func; | ||
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| //--- b.cppm | ||
| module; | ||
| #include "func2.h" | ||
| export module b; | ||
| export using ::func; | ||
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| //--- test.cc | ||
| import a; | ||
| import b; | ||
| bool test() { | ||
| return func(1, 2); | ||
| } | ||
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| #ifdef IGNORE_ODR_VIOLATION | ||
| // expected-no-diagnostics | ||
| #else | ||
| // [email protected]:1 {{'func' has different definitions in different modules;}} | ||
| // [email protected]:1 {{but in 'a.<global>' found a different body}} | ||
| #endif |
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