strip sometimes corrupts pe-i386 or pe-x86_64 executables

[Grzegorz Antoniak]

Hello,

Recently I've found that strip can trash PE executables in some situations. I'm
using strip 2.24.51.20140703 from TDM-GCC distribution, but I've checked also on
strip 2.25 from Cygwin and strip 2.23.2 from MinGW32, and it suffers from the
same issue.

The source code doesn't really matter, but I was testing it on this program:

    $ cat test.cpp
    #include <iostream>

    int main() {
        std::cout << "works\n";
        return 0;
    }

Compilation of the program is standard. The `-gdwarf-4` option isn't the cause
of the problem, because removing it doesn't fix the issue:

    $ g++ -gdwarf-4 -O3 test.cpp -o test

Then I would like to copy debug symbols to external file:

    $ objcopy --only-keep-debug test.exe test.debug

Next step is adding a `gnu_debuglink` information to the executable:

    $ objcopy --add-gnu-debuglink=test.debug test.exe

Up to now, the executable works:

    $ ./test.exe
    works

But, when trying to remove now unnecessary debug symbols from the executable,
strip corrupts the executable:

    $ strip test.exe
    $ ./test.exe
    -bash: ./test.exe: nie można uruchomić pliku binarnego: Exec format error

When running the executable from Windows' explorer, the error box says that
"test.exe is not a valid Win32 application."

However, it appears that strip is working correctly before adding the
`gnu_debuglink` section. So, simply switching two last steps so that strip will
be executed first, resolves the issue:

    $ strip test.exe
    $ objcopy --add-gnu-debuglink=test.debug test.exe
    $ ./test.exe
    works

Should strip behave this way? If the core of the problem is on my side,
shouldn't strip produce an error message instead of corrupting the executable
file?