warning C4003 and errors C2589 and C2059 on: x = s

问题:

This line works correctly in a small test program, but in the program for which I want it, I get the following compiler complaints:

#include <limits>

x = std::numeric_limits<int>::max();

c:\...\x.cpp(192) : warning C4003: not enough actual parameters for macro 'max'
c:\...\x.cpp(192) : error C2589: '(' : illegal token on right side of '::'
c:\...\x.cpp(192) : error C2059: syntax error : '::'

I get the same results with:

#include <limits>
using namespace std;

x = numeric_limits<int>::max();

Why is it seeing max as the macro max(a,b); ?

回答1:

This commonly occurs when including a Windows header that defines a min or max macro. If you're using Windows headers, put #define NOMINMAX in your code, or build with the equivalent compiler switch (i.e. use /DNOMINMAX for Visual Studio).

Note that building with NOMINMAX disables use of the macro in your entire program. If you need to use the min or max operations, use std::min() or std::max() from the <algorithm> header.

回答2:

Other solution would be to wrap function name with parenthesis like this: (std::numeric_limits<int>::max)(). Same applies to std::max.

Not sure it's good solution for this... NOMINMAX is better IMO, but this could be an option in some cases.

回答3:

Some other header file is polluting the global name space with a max macro. You can fix that by undefining the macro:

#undef max
x = std::numeric_limits<int>::max();

回答4:

#ifdef max
#pragma push_macro("max")
#undef max
#define _restore_max_
#endif

#include <limits>

//... your stuff that uses limits

#ifdef _restore_max_
#pragma pop_macro("max")
#undef _restore_max_
#endif

回答5:

Its definition in for me in Visual Studio 2013 (formatted for better spacing...) is as follows:

static _Ty (max)() _THROW0()
{   // return maximum value
    return (FLT_MAX);
}

So I'm just using FLT_MAX. :) This may not be a universal solution, but it works well in my case, so I thought I would share.