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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
44 lines
1.6 KiB
C++
44 lines
1.6 KiB
C++
// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -verify -Wno-vla %s
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// PR11925
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int n;
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int (&f())[n]; // expected-error {{function declaration cannot have variably modified type}}
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namespace PR18581 {
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template<typename T> struct pod {};
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template<typename T> struct error {
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typename T::error e; // expected-error {{cannot be used prior to '::'}}
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};
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struct incomplete; // expected-note {{forward declaration}}
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void f(int n) {
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pod<int> a[n];
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error<int> b[n]; // expected-note {{instantiation}}
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incomplete c[n]; // expected-error {{incomplete}}
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}
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}
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void pr23151(int (&)[*]) { // expected-error {{variable length array must be bound in function definition}}
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}
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void test_fold() {
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char a1[(unsigned long)(int *)0+1]{}; // expected-warning{{variable length array folded to constant array as an extension}}
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char a2[(unsigned long)(int *)0+1] = {}; // expected-warning{{variable length array folded to constant array as an extension}}
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char a3[(unsigned long)(int *)0+1];
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}
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// Demonstrate that the check for a static_assert-like use of VLA does not
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// crash when there's no array size expression at all.
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void test_null_array_size_expr() {
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int array1[]; // expected-error {{definition of variable with array type needs an explicit size or an initializer}}
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int array2[] = { 1, 2, 3 };
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}
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// Show that the check for a static_assert-like use of a VLA properly handles a
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// dependent array size expression.
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template <typename Ty>
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void func(int expr) {
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int array[sizeof(Ty) ? sizeof(Ty{}) : sizeof(int)];
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int old_style_assert[expr ? Ty::one : Ty::Neg_one]; // We don't diagnose as a VLA until instantiation
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}
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