Function std::terminate can be created without type metadata resulting in assertion failure linking libc++ with ThinLTO + cfi-icall

[pcc]

Bugzilla Link	33752
Version	trunk
OS	Linux
CC	@eugenis

Extended Description

$ cat term.cpp namespace test0 { void foo() {}

struct A { A(); ~A(); };

void test() noexcept { A a; foo(); } } // namespace test0

namespace std { void terminate() {} }

void f(void (*p)()) { p(); }

void *g();

int main(int argc, char *argv) { f((void ()())g()); } $ cat term2.cpp namespace std {

void terminate();

}

void g() { return (void )&std::terminate; } $ ~/src2/llvm-project/ra/bin/clang -fsanitize=cfi-icall term.cpp term2.cpp -flto=thin -std=c++11 -fuse-ld=lld ld.lld: lib/Transforms/IPO/LowerTypeTests.cpp:860: void (anonymous namespace)::LowerTypeTestsModule::importFunction(llvm::Function *, bool): Assertion `isDefinition' failed.

[pcc]

r307744 fixes the assertion failure, but the type metadata is still missing.

[pcc]

There are actually two bugs:

• clang fails to add the type metadata to std::terminate
• the assertion failure in the pass

The second issue can be encountered in a relatively common case (mixed CFI + non-CFI compilation). After discussion with Evgeniy I think the right thing to do about functions without type metadata in the pass is to skip them. Then they will basically be treated the same way as functions that are defined outside of the LTO unit (e.g. in a regular object file).

Separately, we need to fix clang so that it adds type metadata to the definition of std::terminate (and perhaps other builtin functions), but that seems less important than fixing the pass.