How to troubleshoot a crash under Cygwin at -O3?

[Jeffrey Walton <noloader at gmail dot com>]

I'm experiencing a crash under Cygwin with -O3. The crash is reproducible:

Program received signal SIGSEGV, Segmentation fault.
DL_GroupParameters_IntegerBased::GetEncodedElementSize (this=0x11,
    reversible=true) at gfpcrypt.h:55
55              unsigned int GetEncodedElementSize(bool reversible)
const {return GetModulus().ByteCount();}

Above, this = 0x11, and I believe its a private exponent (17). I'm
guessing its related to the vtable generated under Cygwin at -O3.

Note that there are no virtual methods. There is a base class that
provides an interface, and then derived classes provide the
implementation. In fact, there's a macro #define CRYPTOPP_NO_VTABLE
__declspec(novtable). (Also see
http://www.cryptopp.com/docs/ref/gfpcrypt_8h_source.html and
http://www.cryptopp.com/docs/ref/gfpcrypt_8cpp_source.html).

*If* I force -fPIC on the command line and endure 135 or so of these:

    $ make
    g++ -DNDEBUG -g -O3 -fPIC -march=native -pipe -c shacal2.cpp
    shacal2.cpp:1:0: warning: -fPIC ignored for target (all code is
position independent)
    // shacal2.cpp - by Kevin Springle, 2003
    ^

Then the program executes fine. But its a very messy compile, and its
probably not going to be worth forcing -fPIC because we will get too
much negative feedback.

How can I begin to troubleshoot the crash under Cygwin at -O3? (Or, if
anyone has seen this in the past, then cut to the chase: what is the
work around?).

*****

$ g++ --version
g++ (GCC) 4.9.3
Copyright (C) 2015 Free Software Foundation, Inc.

$ uname -a
CYGWIN_NT-6.1-WOW windows-7-x64 2.0.4(0.287/5/3) 2015-06-09 12:20 i686 Cygwin