CODEWITHSUNDEEP
c++visual-studio-2010visual-c++-2010
Jayanga Kaushalya
Jayanga Kaushalya

Reputation: 2744

ceil works without including <cmath> in visual c++ 2010

I just wrote a simple C++ program in Visual Studio 2010 and I use ceil function. But I forgot to include the <cmath> and only included the <iostream>. Surprisingly my code compiled successfully and ran without any error. I read a C++ book and it clearly says that to use ceil function you must include <cmath> or <math.h>. Why this happens? Can anyone explain me? Thanks!

Upvotes: 2

Views: 729

Answers (2)

sehe
sehe

Reputation: 393583

The header is indirectly included from some other (indirectly) included header.

To find out which one, enable 'keep preprocessed source' (/P) from the project options and inspect the resulting (*.i) file

Update Just found out that VS2010 has renamed the related option:

enter image description here

Upvotes: 1

Mysticial
Mysticial

Reputation: 471409

Technically speaking, implementations are allowed to automatically include any header in the system headers. But this is implementation defined.

In some cases, <cmath> is already included, in other cases, it isn't - same applies to all the other standard headers.

This issue came up on this question: https://stackoverflow.com/questions/7632926/is-this-a-c-program-or-c-program-how-to-decide

That aside, it's possible that it could be indirectly included by other includes.

Upvotes: 1

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