868783e855
It is possible for both a base and a derived class to be satisfied with a unique vtable. If a program contains casts of the same pointer to both of those types, the CFI checks will be lowered to this (with ThinLTO): if (p != &__typeid_base_global_addr) trap(); if (p != &__typeid_derived_global_addr) trap(); The optimizer may then use the first condition combined with the assumption that __typeid_base_global_addr and __typeid_derived_global_addr may not alias to optimize away the second comparison, resulting in an unconditional trap. This patch fixes the bug by giving imported globals the type [0 x i8]*, which prevents the optimizer from assuming that they do not alias. Differential Revision: https://reviews.llvm.org/D38873 llvm-svn: 315753
26 lines
431 B
C++
26 lines
431 B
C++
// RUN: %clangxx_cfi -o %t %s
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// RUN: %run %t
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// In this example, both __typeid_A_global_addr and __typeid_B_global_addr will
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// refer to the same address. Make sure that the compiler does not assume that
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// they do not alias.
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struct A {
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virtual void f() = 0;
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};
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struct B : A {
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virtual void f() {}
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};
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__attribute__((weak)) void foo(void *p) {
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B *b = (B *)p;
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A *a = (A *)b;
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a->f();
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}
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int main() {
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B b;
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foo(&b);
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}
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