What is the possible use for “#define for if (false) {} else for”?

Question

In another question, I just spotted this little pearl of C wisdom:

#define for if (false) {} else for

which caused MSVC to

Answer 1

The effect was already described.

The reason to have it is to port C++ code to MSVC. Or it is also very helpfull if you want your C++ code platformindependent. For example, you developed it on Linux/MacOSX and now want to compile it in MSVC.

And it is also very usefull for C++ itself. For example:

for(std::set::iterator i = myset.begin(); i != myset.end(); ++i) {
    // ...
}

for(int i = 0; i < N; ++i) {
    // ...
}

I have seen MSVC code which worked around this by doing either:

for(std::set::iterator i1 = myset.begin(); i1 != myset.end(); ++i1) {
    // ...
}

for(int i2 = 0; i2 < N; ++i2) {
    // ...
}

Or:

{for(std::set::iterator i = myset.begin(); i != myset.end(); ++i) {
    // ...
}}

{for(int i = 0; i < N; ++i) {
    // ...
}}

In both cases (imo) not that nice. And this #define is a small hack to make MSVC behave more standard.