Add custom messages in assert?

Question

Is there a way to add or edit the message thrown by assert? I\'d like to use something like

assert(a == b, \"A must be equal to B\");

Then

Answer 1

assert is a macro/function combination. you can define your own macro/function, using __FILE__, __BASE_FILE__, __LINE__ etc, with your own function that takes a custom message

Answer 2

Here's my version of assert macro, which accepts the message and prints everything out in a clear way:

#include <iostream>

#ifndef NDEBUG
#   define M_Assert(Expr, Msg) \
    __M_Assert(#Expr, Expr, __FILE__, __LINE__, Msg)
#else
#   define M_Assert(Expr, Msg) ;
#endif

void __M_Assert(const char* expr_str, bool expr, const char* file, int line, const char* msg)
{
    if (!expr)
    {
        std::cerr << "Assert failed:\t" << msg << "\n"
            << "Expected:\t" << expr_str << "\n"
            << "Source:\t\t" << file << ", line " << line << "\n";
        abort();
    }
}

Now, you can use this

M_Assert(ptr != nullptr, "MyFunction: requires non-null argument");

And in case of failure you will get a message like this:

Assert failed:  MyFunction: requires non-null argument

Expected: ptr != nullptr

Source: C:\MyProject\src.cpp, line 22

Nice and clean, feel free to use it in your code =)