std::min is broken if FMT_HEADER_ONLY is defined.

[DevO2012]

Solution is to put flowing lines just before windows include.

#include <windows.h>
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX

[vitaut]

Thanks for the bug report. I couldn't find any reference to std::min in C++ Format other than in tests which don't use FMT_HEADER_ONLY. Could you post the full error that you get?

[DevO2012]

The problem is that windows.h will define min and max macros.
It will also include a lot of other garbage that usually nobody need.
This will break any usage of std::min and std::max in later code.
I have added pull request about this.

[newnon]

you can just write int a = (std::min)(10, 20); and min max macros will not work and you don't need NOMINMAX

[vitaut]

This is a well-known problem with Windows headers and unfortunately I don't see a good way to address this without potentially breaking user code (which can happen if we unconditionally define NOMINMAX) that also includes windows.h. Possible solutions:

• Use the default non-header-only configuration
• Define NOMINMAX before including format.h or on a project level

@DevO2012 Will it work for you?

[DevO2012]

Yes I know that I can write (std::min)(10, 20) but only in my code not in other libraries that use std::min and std::max.

I don't see a good way to address this without potentially breaking user code (which can happen if we unconditionally define NOMINMAX) that also includes windows.h

Can you please elaborate how this can break user code ?
Do you mean that a lost of users still use preprocessor based min and max, this would be big surprise for me ?

Define NOMINMAX before including format.h or on a project level

Ok this seems to be the most safe solution :)

[vitaut]

Can you please elaborate how this can break user code ?

It can happen if windows.h is included directly or via another header after including format.h and then a min or max macro is used, possibly by code in another header (this can even be C code):

#include <format.h>
#include <windows.h> // can be included in another header, possibly C
max(1, 2); // same as above

Do you mean that a lost of users still use preprocessor based min and max, this would be big surprise for me ?

I hope noone is using min and max macros, but I don't want to break their code if they do. Although they probably deserve their code to be broken =).

Ok this seems to be the most safe solution :)

Cool, I'm closing this issue then, but if you have any ideas on how to improve the situation feel free to reopen it.

[DevO2012]

How about this solution ?

# define WIN32_LEAN_AND_MEAN
# define NOMINMAX
# include <windows.h>
# undef  NOMINMAX
# undef  WIN32_LEAN_AND_MEAN

[vitaut]

I've implemented something similar in 67ce394. Unfortunately it may still break if someone uses min/max macros because NOMINMAX only applies to the first include of windows.h. But it's probably a lesser evil compared to breaking std::min/max and it can be disabled by defining FMT_WIN_MINMAX. In any case this only applies to the header-only configuration so it's not that important. Thanks @DevO2012.