Wrong code:
i586-mingw32msvc-g++ (GCC) 4.4.4 (on Ubuntu)
Correct code:
i586-mingw32msvc-g++ (Gentoo 4.5.2 p1.0, pie-0.4.5) 4.5.2

Build with:
i586-mingw32msvc-g++ -O0 -fstack-protector -o wtf.exe wtf.cpp

Apparent problem:
The function theCompilerWorks() returns false due to the return value true in the al register being clobbered by __Unwind_SjLj_Unregister.

The problem only occurs at -O0 in this test case, but the original program fails at -O2.

May be related to:
Bug 30047 mentions a return value being clobbered by __Unwind_SjLj_Unregister.

Testcase:
-----
extern "C" void abort(void);

void a() {}

void (*volatile doNothing)() = a;

struct TheCompilerWorks
{
	TheCompilerWorks() {}
	~TheCompilerWorks() {}
	char unusedArray[340];
};

bool theCompilerWorks()
{
	TheCompilerWorks harmlessObject;
	doNothing();
	return true;
}

int main()
{
	if (!theCompilerWorks())
		abort();
}
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