84a3aadf0f
Reapplication of 7339c0f782d5c70e0928f8991b0c05338a90c84c with a fix for a crash involving arrays without a size expression. Clang supports VLAs in C++ as an extension, but we currently only warn on their use when you pass -Wvla, -Wvla-extension, or -pedantic. However, VLAs as they're expressed in C have been considered by WG21 and rejected, are easy to use accidentally to the surprise of users (e.g., https://ddanilov.me/default-non-standard-features/), and they have potential security implications beyond constant-size arrays (https://wiki.sei.cmu.edu/confluence/display/c/ARR32-C.+Ensure+size+arguments+for+variable+length+arrays+are+in+a+valid+range). C++ users should strongly consider using other functionality such as std::vector instead. This seems like sufficiently compelling evidence to warn users about VLA use by default in C++ modes. This patch enables the -Wvla-extension diagnostic group in C++ language modes by default, and adds the warning group to -Wall in GNU++ language modes. The warning is still opt-in in C language modes, where support for VLAs is somewhat less surprising to users. RFC: https://discourse.llvm.org/t/rfc-diagnosing-use-of-vlas-in-c/73109 Fixes https://github.com/llvm/llvm-project/issues/62836 Differential Revision: https://reviews.llvm.org/D156565
31 lines
1.2 KiB
C++
31 lines
1.2 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wvla-extension %s
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struct StillPOD {
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StillPOD() = default;
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};
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struct StillPOD2 {
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StillPOD np;
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};
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struct NonPOD {
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NonPOD(int) {}
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};
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struct POD {
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int x;
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int y;
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};
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// We allow VLAs of POD types, only.
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void vla(int N) { // expected-note 5{{here}}
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int array1[N]; // expected-warning{{variable length arrays in C++ are a Clang extension}} expected-note {{parameter 'N'}}
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POD array2[N]; // expected-warning{{variable length arrays in C++ are a Clang extension}} expected-note {{parameter 'N'}}
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StillPOD array3[N]; // expected-warning{{variable length arrays in C++ are a Clang extension}} expected-note {{parameter 'N'}}
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StillPOD2 array4[N][3]; // expected-warning{{variable length arrays in C++ are a Clang extension}} expected-note {{parameter 'N'}}
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NonPOD array5[N]; // expected-error{{no matching constructor for initialization of 'NonPOD[N]'}}
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// expected-warning@-1{{variable length arrays in C++ are a Clang extension}} expected-note@-1 {{parameter 'N'}}
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// expected-note@-16{{candidate constructor not viable}}
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// expected-note@-18{{candidate constructor (the implicit copy constructor) not viable}}
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// expected-note@-19{{candidate constructor (the implicit move constructor) not viable}}
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}
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