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[Sema] Handle transparent_union attributes in C mode only 

This commit marks the transparent_union attributes as C only because clang
doesn't support them in C++ mode. Prior to this commit, clang still tried to
verify these attributes in C++, leading to crashes when analyzing templated
transparent_union unions that have dependent field types. This commit ensures
that such crashes won't happen again.

As a result of this commit clang now displays a warning every time it encounters
a transparent_union attribute in C++ mode.

Differential Revision: https://reviews.llvm.org/D25308

llvm-svn: 283995
This commit is contained in:
Alex Lorenz 2016-10-12 09:36:35 +00:00
parent 883cc25d9f
commit 757a69b760
2 changed files with 17 additions and 0 deletions
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1
clang/include/clang/Basic/Attr.td
View File

@ -1543,6 +1543,7 @@ def TransparentUnion : InheritableAttr {
let Spellings = [GCC<"transparent_union">];
// let Subjects = SubjectList<[Record, TypedefName]>;
let Documentation = [Undocumented];
let LangOpts = [COnly];
}
def Unavailable : InheritableAttr {

16
clang/test/SemaCXX/attr-gnu.cpp
View File

@ -27,3 +27,19 @@ public:
void test3() __attribute__((cf_unknown_transfer)) override {} // Ok, not known to GCC.
};
}
template<typename T>
union Tu { T b; } __attribute__((transparent_union)); // expected-warning {{'transparent_union' attribute ignored}}
template<typename T>
union Tu2 { int x; T b; } __attribute__((transparent_union)); // expected-warning {{'transparent_union' attribute ignored}}
union Tu3 { int x; } __attribute((transparent_union)); // expected-warning {{'transparent_union' attribute ignored}}
void tuTest1(Tu<int> u); // expected-note {{candidate function not viable: no known conversion from 'int' to 'Tu<int>' for 1st argument}}
void tuTest2(Tu3 u); // expected-note {{candidate function not viable: no known conversion from 'int' to 'Tu3' for 1st argument}}
void tu() {
int x = 2;
tuTest1(x); // expected-error {{no matching function for call to 'tuTest1'}}
tuTest2(x); // expected-error {{no matching function for call to 'tuTest2'}}
}