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I’m using g++ 4.9.2 on Debian 8, x86_64. I’m catching a Undefined Behavior sanitizer (UBsan) (-fsanitize=undefined) error:

algebra.cpp:206:8: runtime error: load of value 127,
    which is not a valid value for type 'bool'

The code is from the Crypto++ library. Here is the code at algebra.cpp:206 (and some related code):

206   struct WindowSlider
207   {
208     WindowSlider(const Integer &expIn, bool fastNegate, unsigned int windowSizeIn=0)
209         : m_exp(expIn), m_windowModulus(Integer::One()), m_windowSize(windowSizeIn), m_windowBegin(0), m_fastNegate(fastNegate), m_firstTime(true), m_finished(false)
210     {
            ...
249         Integer m_exp, m_windowModulus;
250         unsigned int m_windowSize, m_windowBegin;
251         word32 m_expWindow;
252         bool m_fastNegate, m_negateNext, m_firstTime, m_finished;
253     };

Its called in a couple of places, like:

$ grep -I WindowSlider *
...
algebra.cpp:    std::vector<WindowSlider> exponents;
algebra.cpp:        exponents.push_back(WindowSlider(*expBegin++, InversionIsFast(), 0));
ecp.cpp:    std::vector<WindowSlider> exponents;
ecp.cpp:        exponents.push_back(WindowSlider(*expBegin++, InversionIsFast(), 5));

InversionIsFast is a bool, so that should not be a problem. But I added !!InversionIsFast() just in case and the issue persists.

EDIT: Here is a grep for InversionIsFast. It appears it is initialized.

$ grep -I InversionIsFast *
algebra.cpp:        exponents.push_back(WindowSlider(*expBegin++, !!InversionIsFast(), 0));
algebra.h:  virtual bool InversionIsFast() const {return false;}
ec2n.h: bool InversionIsFast() const {return true;}
ecp.cpp:        exponents.push_back(WindowSlider(*expBegin++, !!InversionIsFast(), 5));
ecp.h:  bool InversionIsFast() const {return true;}

I also initialized m_negateNext in the ctor.

What is the issue, and how do I clear it?