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Why should I not #include <bits/stdc++.h>?

I posted a question with my code whose only #include directive was the following:

#include <bits/stdc++.h>

My teacher told me to do this, but in the comments section I was informed that I shouldn't.

Why?

Solution

  • Including <bits/stdc++.h> appears to be an increasingly common thing to see on Stack Overflow, perhaps something newly added to a national curriculum in the current academic year.

    I imagine the advantages are vaguely given thus:

    • You only need write one #include line.
    • You do not need to look up which standard header everything is in.

    Unfortunately, this is a lazy hack, naming a GCC internal header directly instead of individual standard headers like <string>, <iostream> and <vector>. It ruins portability and fosters terrible habits.

    The disadvantages include:

    • It will probably only work on that compiler.
    • You have no idea what it'll do when you use it, because its contents are not set by a standard.
    • Even just upgrading your compiler to its own next version may break your program.
    • Every single standard header must be parsed and compiled along with your source code, which is slow and results in a bulky executable under certain compilation settings.

    Don't do it!

    More information:

    Example of why Quora is bad: