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Don't warn about selectany on implicitly inline variables

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Summary:
This avoids a -Wignored-attribute warning on the code pattern Microsoft
recommends for integral const static data members defined in headers
here:
https://docs.microsoft.com/en-us/cpp/build/reference/microsoft-extensions-to-c-and-cpp?view=vs-2019

The attribute is redundant, but it is necessary when compiling in C++14
modes with /Za, which disables MSVC's extension that treats such
variables as implicitly inline.

Fixes PR43270

Reviewers: epastor, thakis, hans

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67426

llvm-svn: 371749
This commit is contained in:
Reid Kleckner 2019-09-12 17:55:48 +00:00
parent 6943472d45
commit b00a49d1b3
2 changed files with 27 additions and 0 deletions
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9
clang/lib/Sema/SemaDecl.cpp
View File

@ -2652,6 +2652,15 @@ static void checkNewAttributesAfterDef(Sema &S, Decl *New, const Decl *Old) {
--E;
continue;
}
} else if (isa<SelectAnyAttr>(NewAttribute) &&
cast<VarDecl>(New)->isInline() &&
!cast<VarDecl>(New)->isInlineSpecified()) {
// Don't warn about applying selectany to implicitly inline variables.
// Older compilers and language modes would require the use of selectany
// to make such variables inline, and it would have no effect if we
// honored it.
++I;
continue;
}
S.Diag(NewAttribute->getLocation(),

18
clang/test/SemaCXX/declspec-selectany.cpp Normal file
View File

@ -0,0 +1,18 @@
// RUN: %clang_cc1 -std=c++14 %s -triple x86_64-windows-msvc -fdeclspec -verify
// RUN: %clang_cc1 -std=c++17 %s -triple x86_64-windows-msvc -fdeclspec -verify
// RUN: %clang_cc1 -std=c++14 %s -triple x86_64-scei-ps4 -fdeclspec -verify
// MSVC emits this error too.
const int __declspec(selectany) test1 = 0; // expected-error {{'selectany' can only be applied to data items with external linkage}}
extern const int test2;
const int test2 = 42; // expected-note {{previous definition is here}}
extern __declspec(selectany) const int test2; // expected-warning {{attribute declaration must precede definition}}
extern const int test3;
const int __declspec(selectany) test3 = 42; // Standard usage.
struct Test4 {
static constexpr int sdm = 0;
};
__declspec(selectany) constexpr int Test4::sdm; // no warning