Bizarre Undeclared Variable Compiler Error - c++

Question

Problem: The compiler declares a seemingly nonsensical error that a local variable in a class member function "was not declared in this scope". The code shown below is a simplified implementation of the original function, and somehow it still triggers the same error. Furthermore, the error disappears whenever I rename the variable (in each place it's used) and resumes as soon as I change the variable back to its original name ("minor"). I don't understand this behavior and can't find any information/posts on what would cause a compiler to do this. Could someone kindly offer suggestions on what might be wrong? Is it indicative of a major bug somewhere else in my code (e.g. the Matrix class definition)?
Details: I'm compiling on Linux Mint 18 using g++ on Makefiles generated by CMake. I've tried with and without a variety of compiler options (e.g. -O2, -Wall, etc.), and the result is unchanged. I've previously compiled and ran a slightly earlier version of this code/project on Windows 7 using MinGW and a self-written Makefile with no problems. I'm happy to provide additional details upon request.
Modified/minimalist code snippet from Matrix.cpp:
Matrix Matrix::BuildCofactorMatrix() const {
double minor (0.0);
minor = 1.0;
return Matrix(height_, width_);
}
Warning message:
/PATH-TO-PROJECT-ROOT/src/Matrix.cpp: In member function ‘Matrix Matrix::BuildCofactorMatrix() const’:
/PATH-TO-PROJECT-ROOT/src/Matrix.cpp:1123:5: error: ‘minor’ was not declared in this scope
minor = 1.0;
2017-08-21 Edit:
I removed unnecessary code and created a truly "Minimal, Complete, and Verifiable" example of the problem. For me, the error seems to be a function of the iostream library. If I remove the iostream inclusion, the problem seems to disappear. However, the error also depends on the c++ standard used for compiling. When I specify that g++ use, for example, -std=c++11 or -std=c++14, the problem persists, but once I remove the specification (i.e. g++ -c Matrix.cpp), the error disappears. By the way, I'm using g++ 4:5.3.1-1ubu.
Unless I'm missing something, I can't find any macros in iostream, istream, ostream, or ios that mention the term "minor", but perhaps it's further up the inclusion chain...?
Matrix.hpp:
#ifndef MATRIX_HPP
#define MATRIX_HPP
class Matrix {
public:
void BuildCofactorMatrix() const;
};
#endif
Matrix.cpp:
#include "Matrix.hpp"
#include <iostream>
void Matrix::BuildCofactorMatrix() const {
double minor (0.0);
minor = 0.0;
}

Answer 1

I can replicate the problem by adding #define minor(x) (x) before the function.
The macro matches minor(0.0) but not minor without the "parameter".
The line
double minor (0.0);
would be replaced by
double (0.0);
which is a valid, but useless, type cast.
So, go look for some evil macro in one of the include files.