c++ - How to solve "'isnan' was not declared in this scope" without upgrading GCC?

Question

I am using GCC 5.4 and getting 'isnan' was not declared in this scope error. I found <cmath> hides isnan in <math.h> in C++14 / C++11?.

but I have to keep the GCC version, without modifying the source which uses isnan, and C++14 standard. so I want to know any trick to solve it.

for example: define isnan=std::isnan as compile -D argument?

question from:https://stackoverflow.com/questions/66059029/how-to-solve-isnan-was-not-declared-in-this-scope-without-upgrading-gcc

Answer 1

Waitting for answers