[Bug c++/47490] New: __Unwind_SjLj_Unregister clobbers return value with i586-mingw32msvc-g++ 4.4.4 and -fstack-protector

[cyp561 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47490

           Summary: __Unwind_SjLj_Unregister clobbers return value with
                    i586-mingw32msvc-g++ 4.4.4 and -fstack-protector
           Product: gcc
           Version: 4.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: cyp...@gmail.com
              Host: Ubuntu, 64-bit
            Target: i586-mingw32msvc


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();
}
-----