552c6c2328
Old GCC used to aggressively fold VLAs to constant-bound arrays at block scope in GNU mode. That's non-conforming, and more modern versions of GCC only do this at file scope. Update Clang to do the same. Also promote the warning for this from off-by-default to on-by-default in all cases; more recent versions of GCC likewise warn on this by default. This is still slightly more permissive than GCC, as pointed out in PR44406, as we still fold VLAs to constant arrays in structs, but that seems justifiable given that we don't support VLA-in-struct (and don't intend to ever support it), but GCC does. Differential Revision: https://reviews.llvm.org/D89523
36 lines
1.1 KiB
C
36 lines
1.1 KiB
C
// RUN: %clang_cc1 -triple x86_64-linux -std=c17 -verify=expected,norounding %s
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// RUN: %clang_cc1 -triple x86_64-linux -std=gnu17 -verify=expected,norounding %s
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// RUN: %clang_cc1 -triple x86_64-linux -std=c17 -verify=expected,rounding %s -frounding-math
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// RUN: %clang_cc1 -triple x86_64-linux -std=gnu17 -verify=expected,rounding %s -frounding-math
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#define fold(x) (__builtin_constant_p(x) ? (x) : (x))
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double a = 1.0 / 3.0;
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#define f(n) ((n) * (1.0 / 3.0))
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_Static_assert(fold((int)f(3)) == 1, "");
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typedef int T[fold((int)f(3))];
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typedef int T[1];
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enum Enum { enum_a = (int)f(3) };
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struct Bitfield {
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unsigned int n : 1;
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unsigned int m : fold((int)f(3));
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};
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void bitfield(struct Bitfield *b) {
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b->n = (int)(6 * (1.0 / 3.0)); // norounding-warning {{changes value from 2 to 0}}
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}
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void vlas() {
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// This is always a VLA due to its syntactic form.
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typedef int vla1[(int)(-3 * (1.0 / 3.0))];
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struct X1 { vla1 v; }; // expected-error {{fields must have a constant size}}
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// This is always folded to a constant.
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typedef int vla2[fold((int)(-3 * (1.0 / 3.0)))]; // expected-error {{negative size}}
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struct X2 { vla2 v; };
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}
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