Re: [boost] WCHAR_MAX not defined on openbsd

Subject: Re: [boost] WCHAR_MAX not defined on openbsd
From: Kim Barrett (kab.conundrums_at_[hidden])
Date: 2010-08-15 19:11:13

On Aug 15, 2010, at 12:09 PM, John Maddock wrote:

>> hi there, i'm using openbsd 4.7 with g++ 4.2.4 installed from openbsd
>> packages.
>> i've tried building both boost 1.43 and 1.44rc, and both have several
>> libraries fail due to WCHAR_MAX not being defined. this appears to be
>> because __STDC_LIMIT_MACROS is not defined while processing
>> /usr/include/stdint.h. i built boost with
>> ./bjam cxxflags='-D__STDC_LIMIT_MACROS' and there are no more errors about
>> WCHAR_MAX not being defined. perhaps this define should be added to
>> boost/cstdint.hpp, or is there a deeper reason why WCHAR_MAX is not being
>> defined correctly?
> 
> The std doesn't specify that some magic macro has to be defined before WCHAR_MAX gets defined

The C++ standard doesn't, but the C99 standard does!  See footnote in 7.18.2 Limits of specified-width integer types.  This is one of several places where C99 added features to C89 and notes that "C++ implementations should define these macros only when ..." some specified macro is defined before the relevant header is included.

> - in any case by the time a boost header is #included it's too late to define such a macro because the system header may have already been #included by the program.

Which of course makes that C99-specified behavior a real pain to deal with.

And of course that specified behavior is probably quite wrong for C++0x, but the C99 standard doesn't mention the scope of that behavior.  And to add to the confusion, it is worded as a "should" rather than a "shall".