84a3aadf0f
Reapplication of 7339c0f782 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
67 lines
2.1 KiB
C++
67 lines
2.1 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -std=c++11 %s -verify
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// RUN: %clang_cc1 -fsyntax-only -std=c++1y %s -verify -DCPP1Y
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void missing_lambda_declarator() {
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[](){}();
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}
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template<typename T> T get();
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void infer_void_return_type(int i) {
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if (i > 17)
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return []() { }();
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if (i > 11)
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return []() { return; }();
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return [](int x) {
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switch (x) {
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case 0: return get<void>();
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case 1: return;
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case 2: return { 1, 2.0 }; //expected-error{{cannot deduce}}
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}
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}(7);
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}
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struct X { };
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X infer_X_return_type(X x) {
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return [&x](int y) {
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if (y > 0)
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return X();
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else
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return x;
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}(5);
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}
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X infer_X_return_type_2(X x) {
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return [x](int y) {
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if (y > 0)
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return X();
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else
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return x; // ok even in c++11, per dr1048.
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}(5);
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}
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struct Incomplete; // expected-note 2{{forward declaration of 'Incomplete'}}
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void test_result_type(int N) { // expected-note {{declared here}}
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auto l1 = [] () -> Incomplete { }; // expected-error{{incomplete result type 'Incomplete' in lambda expression}}
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typedef int vla[N]; // expected-warning {{variable length arrays in C++ are a Clang extension}} \
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expected-note {{function parameter 'N' with unknown value cannot be used in a constant expression}}
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auto l2 = [] () -> vla { }; // expected-error{{function cannot return array type 'vla' (aka 'int[N]')}}
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}
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template <typename T>
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void test_result_type_tpl(int N) { // expected-note 2{{declared here}}
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auto l1 = []() -> T {}; // expected-error{{incomplete result type 'Incomplete' in lambda expression}}
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// expected-note@-1{{while substituting into a lambda expression here}}
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typedef int vla[N]; // expected-warning 2{{variable length arrays in C++ are a Clang extension}} \
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expected-note 2{{function parameter 'N' with unknown value cannot be used in a constant expression}}
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auto l2 = []() -> vla {}; // expected-error{{function cannot return array type 'vla' (aka 'int[N]')}}
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}
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void test_result_type_call() {
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test_result_type_tpl<Incomplete>(10); // expected-note 2{{requested here}}
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}
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