decltype crash breaks is_constructable

[llvmbot]

Bugzilla Link	11131
Resolution	FIXED
Resolved on	Oct 14, 2011 15:34
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@tkremenek

Extended Description

The following test case is reduced libc++'s is_constructable. The case causes clang to segfault. This bug arose in a boost test case. It's hard to track down exactly what is going on in boost, because (as always) there are many levels of code, and clang is crashing.

struct S;

struct __any
{
__any(...);
};

template
T& D();

template <class _Tp, class ..._Args>
decltype(D<_Args>()...)
X(_Tp&&, _Args&& ...);

template <class ..._Args>
int
X(__any, _Args&& ...);

decltype(X(D(), D())) j;

[tkremenek]

cloned to rdar://problem/10288375

[DougGregor]

Chris, do you have the original preprocessed sources (even if they aren't at all reduced)? This code is invalid, and while we shouldn't crash on it, I'm concerned that it doesn't trigger the same bug you're seeing.

[DougGregor]

Nevermind! I see how this would be triggered from valid code. Further reduction:

struct S;

S &getS();

void f(...);

void g() {
sizeof(f(getS()));
}

[DougGregor]

Fixed in Clang r141986.