Instead of doing this:

    #define ASSERT_EQ(a, b) \
        do \
        { \
            if ( (a) == (b) ) break; \
                                                                \
            std::fprintf(stderr, #a " != " #b " at %s:%d\n", \
                            __FILE__, __LINE__); \
            std::abort(); \
        } while (0)

Wouldn't it be nice to be able to do this:

    #define ASSERT_EQ(a, b) \\\
        do
        {
            if ( (a) == (b) ) break;

            std::fprintf(stderr, #a " != " #b " at %s:%d\n",
                            __FILE__, __LINE__);
            std::abort();
        } while (0)
    \\\

I'm told back in the 1990's, a guy called Andrew Myers made a patch
for GNU gcc so that you could do:

    #begin define swap(x,y,T)
    do {
       T temp = x;
        x = y;
        y = temp;
    } while (0)
    #end

Whether we use three backslashes or "'#begin define", this should be
standardised in C++29.