C++ initialization list for class with "min" member

Question

I have seen a class where someone named member variables min and max

class A
{
public:
 A();
 ~A();
 bool min;
 bool max;
 ...
};

with a constructor

A::A()
{
  min=false;
  max=true;
  ...
}

I have tried to rewrite it with usage of an initialization list:

A::A():min(false), max(true){}

but I have received an warning + error

warning C4003: not enough actual parameters for macro 'min'
error C2059: syntax error : ')'

because min macro is defined in WinDef.h

Is it possible to use initialization list in this situation without renaming of the member variables?

@edtheprogrammerguy No: `error C2059: syntax error : 'this'` — Peter Petrik, Oct 01 '14 at 13:27
@edtheprogrammerguy: In C++ it would be `this->` but that's still part of an expression, and the initializer list contains members not epxressions. — MSalters, Oct 01 '14 at 13:29
I'd spell the member names out as `minimum` and `maximum` and avoid this mess, but that's just me. — Mike DeSimone, Oct 01 '14 at 13:51
This is a great example of why macros should generally be avoided as they just stomp all over everything regardless of context. — Lionel, Oct 01 '14 at 13:55
Wait until you start using standard algorithms like `min` and `max`. Best is to avoid those windows headers as much as possible. — Sebastian Mach, Oct 01 '14 at 14:41

score 5 · Accepted Answer · answered Oct 01 '14 at 13:36

If you have VS2013 or another modern compiler:

A():min {false}, max {true} { }

avoids the problem because min(a,b) is a function-style macro and { can't start its argument list.

This is specific to initializer lists, so I've reopened the question. The "duplicate" suggested addresses macro use in expression context, which is fundamentally different - you can use (min) there.

Lionel · Answer 2 · 2014-10-02T08:08:49.063

1

Depending on your situation you have several options.

Use brace initialisation as suggested by @MSalters
Define NOMINMAX before you include the windows header files to avoid the min and max macros from being defined. This will depend on how big your code is and how much control you have over it.
Just #undef the macros. Only recommend in a source file.
Use MSVC pre-processor directives to save, undef then restore the macros. Like so...
```
#pragma push_macro("min")
#undef min
/* use min here */
#pragma pop_macro("min")
```

edited Oct 02 '14 at 08:08

answered Oct 01 '14 at 13:48

Lionel

326
1
4

The downside to defining `NOMINMAX` is that other sources might be expecting `min` and `max` to exist. – Mike DeSimone Oct 01 '14 at 13:53
@MikeDeSimone Yes exactly, the same is true for using `#undef`, you have to be careful where you put that and what code could potentially be compiled after. – Lionel Oct 01 '14 at 13:59
1

@MikeDeSimone: That might be solved by a further `using std::min; using std::max`. It's quite uncommon for code to depend on `min` and `max` being macro's. – MSalters Oct 02 '14 at 07:11

C++ initialization list for class with "min" member

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