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This patch covers Core issues about language linkage during declaration matching resolved in [P1787R6](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1787r6.html), namely [CWG563](https://cplusplus.github.io/CWG/issues/563.html) and [CWG1818](https://cplusplus.github.io/CWG/issues/1818.html). [CWG563](https://cplusplus.github.io/CWG/issues/563.html) "Linkage specification for objects" ----------- [P1787R6](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1787r6.html): > [CWG563](https://cplusplus.github.io/CWG/issues/563.html) is resolved by simplifications that follow its suggestions. Wording ([[dcl.link]/5](https://eel.is/c++draft/dcl.link#5)): > In a [linkage-specification](https://eel.is/c++draft/dcl.link#nt:linkage-specification), the specified language linkage applies to the function types of all function declarators and to all functions and variables whose names have external linkage[.](https://eel.is/c++draft/dcl.link#5.sentence-5) Now the wording clearly says that linkage-specification applies to variables with external linkage. [CWG1818](https://cplusplus.github.io/CWG/issues/1818.html) "Visibility and inherited language linkage" ------------ [P1787R6](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1787r6.html): > [CWG386](http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#386), [CWG1839](http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1839), [CWG1818](http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1818), [CWG2058](http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#2058), [CWG1900](http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1900), and Richard’s observation in [“are non-type names ignored in a class-head-name or enum-head-name?”](http://lists.isocpp.org/core/2017/01/1604.php) are resolved by describing the limited lookup that occurs for a declarator-id, including the changes in Richard’s [proposed resolution for CWG1839](http://wiki.edg.com/pub/Wg21cologne2019/CoreWorkingGroup/cwg1839.html) (which also resolves CWG1818 and what of CWG2058 was not resolved along with CWG2059) and rejecting the example from [CWG1477](http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1477). Wording ([[dcl.link]/6](https://eel.is/c++draft/dcl.link#6)): > A redeclaration of an entity without a linkage specification inherits the language linkage of the entity and (if applicable) its type[.](https://eel.is/c++draft/dcl.link#6.sentence-2). Answer to the question in the example is `extern "C"`, and not linkage mismatch. Further analysis of the example is provided as inline comments in the test itself. Note that https://eel.is/c++draft/dcl.link#7 does NOT apply in this example, as it's focused squarely at declarations that are already known to have C language linkage, and declarations of variables in the global scope.
17 lines
1.0 KiB
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17 lines
1.0 KiB
C++
// RUN: %clang_cc1 -std=c++98 %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// RUN: %clang_cc1 -std=c++11 %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// RUN: %clang_cc1 -std=c++14 %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// RUN: %clang_cc1 -std=c++17 %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// RUN: %clang_cc1 -std=c++20 %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// RUN: %clang_cc1 -std=c++23 %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// RUN: %clang_cc1 -std=c++2c %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors -ast-dump | FileCheck %s
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// expected-no-diagnostics
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namespace cwg563 { // cwg563: 3.3
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extern "C" int a;
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} // namespace cwg563
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// CHECK: LinkageSpecDecl {{.*}} C
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// CHECK-NEXT: `-VarDecl {{.*}} a 'int'
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