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
41 lines
1.6 KiB
C++
41 lines
1.6 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -verify %s -triple=i686-pc-linux-gnu -std=c++11
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using size_t = decltype(sizeof(0));
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struct noreturn_t {} constexpr noreturn = {};
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void *operator new [[noreturn]] (size_t, noreturn_t);
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void operator delete [[noreturn]] (void*, noreturn_t);
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void good_news()
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{
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auto p = new int[2][[]];
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auto q = new int[[]][2];
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auto r = new int*[[]][2][[]];
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auto s = new (int(*[[]])[2][[]]);
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}
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void bad_news(int *ip)
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{
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// attribute-specifiers can go almost anywhere in a new-type-id...
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auto r = new int[[]{return 1;}()][2]; // expected-error {{expected ']'}}
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auto s = new int*[[]{return 1;}()][2]; // expected-error {{expected ']'}}
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// ... but not here:
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auto t = new (int(*)[[]]); // expected-error {{an attribute list cannot appear here}}
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auto u = new (int(*)[[]{return 1;}()][2]); // expected-error {{C++11 only allows consecutive left square brackets when introducing an attribute}} \
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expected-error {{variably modified type}} \
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expected-error {{a lambda expression may not appear inside of a constant expression}} \
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expected-warning {{variable length arrays in C++ are a Clang extension}} \
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expected-note-re {{non-literal type '(lambda at {{.*}})' cannot be used in a constant expression}}
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}
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void good_deletes()
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{
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delete [&]{ return (int*)0; }();
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}
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void bad_deletes()
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{
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// 'delete []' is always array delete, per [expr.delete]p1.
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delete []{ return (int*)0; }(); // expected-error {{'[]' after delete interpreted as 'delete[]'}}
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}
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