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This builtin returns the address of a global instance of the `std::source_location::__impl` type, which must be defined (with an appropriate shape) before calling the builtin. It will be used to implement std::source_location in libc++ in a future change. The builtin is compatible with GCC's implementation, and libstdc++'s usage. An intentional divergence is that GCC declares the builtin's return type to be `const void*` (for ease-of-implementation reasons), while Clang uses the actual type, `const std::source_location::__impl*`. In order to support this new functionality, I've also added a new 'UnnamedGlobalConstantDecl'. This artificial Decl is modeled after MSGuidDecl, and is used to represent a generic concept of an lvalue constant with global scope, deduplicated by its value. It's possible that MSGuidDecl itself, or some of the other similar sorts of things in Clang might be able to be refactored onto this more-generic concept, but there's enough special-case weirdness in MSGuidDecl that I gave up attempting to share code there, at least for now. Finally, for compatibility with libstdc++'s <source_location> header, I've added a second exception to the "cannot cast from void* to T* in constant evaluation" rule. This seems a bit distasteful, but feels like the best available option. Reviewers: aaron.ballman, erichkeane Differential Revision: https://reviews.llvm.org/D120159
106 lines
3.7 KiB
C++
106 lines
3.7 KiB
C++
// RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -fexceptions -verify -DTEST=1 %s
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// RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -fexceptions -verify -DTEST=2 %s
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// RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -fexceptions -verify -DTEST=3 %s
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// RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -fexceptions -verify -DTEST=4 %s
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// RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -fexceptions -verify -DTEST=5 %s
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#if TEST == 1
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auto test1a = __builtin_source_location(); // expected-error {{'std::source_location::__impl' was not found}}
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namespace std {
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inline namespace NS {
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struct source_location;
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}
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}
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auto test1b = __builtin_source_location(); // expected-error {{'std::source_location::__impl' was not found}}
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namespace std {
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inline namespace NS {
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struct source_location {
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struct __impl;
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};
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}
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}
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auto test1c = __builtin_source_location(); // expected-error {{'std::source_location::__impl' was not found}}
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#elif TEST == 2
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auto test2a = __builtin_source_location(); // expected-error {{'std::source_location::__impl' was not found}}
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namespace std {
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inline namespace NS {
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struct source_location {
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struct __impl { int x; };
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};
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}
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}
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auto test2b = __builtin_source_location(); // expected-error {{'std::source_location::__impl' must be standard-layout and have only two 'const char *' fields '_M_file_name' and '_M_function_name', and two integral fields '_M_line' and '_M_column'}}
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#elif TEST == 3
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namespace std {
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struct source_location {
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struct __impl {
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int other_member;
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char _M_line;
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const char *_M_file_name;
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char _M_column;
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const char *_M_function_name;
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};
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};
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}
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auto test3 = __builtin_source_location(); // expected-error {{'std::source_location::__impl' must be standard-layout and have only two 'const char *' fields '_M_file_name' and '_M_function_name', and two integral fields '_M_line' and '_M_column'}}
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#elif TEST == 4
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namespace std {
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struct source_location {
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struct parent {};
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struct __impl : public parent {
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char _M_line;
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const char *_M_file_name;
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char _M_column;
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const char *_M_function_name;
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};
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};
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}
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auto test4 = __builtin_source_location(); // expected-error {{'std::source_location::__impl' must be standard-layout and have only two 'const char *' fields '_M_file_name' and '_M_function_name', and two integral fields '_M_line' and '_M_column'}}
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#elif TEST == 5
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namespace std {
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struct source_location {
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struct __impl {
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signed char _M_line; // odd integral type to choose, but ok!
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const char *_M_file_name;
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signed char _M_column;
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const char *_M_function_name;
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static int other_member; // static members are OK
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};
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using BuiltinT = decltype(__builtin_source_location()); // OK.
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};
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}
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// Verify that the address cannot be used as a non-type template argument.
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template <auto X = __builtin_source_location()>
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auto fn1() {return X;} // expected-note {{candidate template ignored: substitution failure: non-type template argument does not refer to any declaration}}
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auto test5a = fn1<>(); // expected-error {{no matching function for call to 'fn1'}}
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// (But using integer subobjects by value is okay.)
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template <auto X = __builtin_source_location()->_M_column>
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auto fn2() {return X;}
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auto test5b = fn2<>();
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// While it's not semantically required, for efficiency, we ensure that two
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// source-locations with the same content will point to the same object. Given
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// the odd definition of the struct used here (using 'signed char'), any
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// line-number modulo 256 will thus have the same content, and be deduplicated.
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#line 128
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constexpr auto sl1 = __builtin_source_location();
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#line 384
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constexpr auto sl2 = __builtin_source_location();
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constexpr auto sl3 = __builtin_source_location();
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static_assert(sl1 == sl2);
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static_assert(sl1 != sl3);
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static_assert(sl1->_M_line == -128);
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#endif
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