[Proj] [MS Windows] PVALUE causes problems with mingw64compilers

[sisyphus1 at optusnet.com.au]

-----Original Message----- 
From: Howard Butler
Sent: Thursday, May 21, 2015 10:43 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] [MS Windows] PVALUE causes problems with 
mingw64compilers


>> On May 21, 2015, at 5:04 AM, sisyphus1 at optusnet.com.au wrote:
>>
>>
>> Is it worth going to the trouble of changing the PVALUE symbol to (say)
>> PROJVALUE for mingw compilers only - but letting the PVALUE symbol stand
>> with non-mingw compilers:
>
> I don’t think so. I think it should just be changed. The folks using 
> projects.h have known it was a bit sketchy to be using (we tried to take 
> it away once already). The next windows person using proj.4 with an 
> interesting include scenario will run into again if we monkey patch the 
> mingw case only.
>
> Let’s just rename it, unless someone has a strong objection.

Renaming it is *definitely* my preferred option.

However, following on from an idea presented by David Mertens on the 
pdl-devel mailing list, I do have a slight refinement to the above idea of 
allowing 2 symbols.

Change:

typedef union { double  f; int  i; char *s; } PVALUE;

to something like:

typedef union { double  f; int  i; char *s; } PROJVALUE;

and then insert:

/* The following is for backwards compatibility. */
/* PVALUE is deprecated - use PROJVALUE       */
#ifndef _WINREG_ /* _WINREG_ is defined by winreg.h */
#define PVALUE PROJVALUE
#endif

And then, in the proj source, replace all other instances of PVALUE with 
PROJVALUE.
Also document PVALUE as being deprecated and will be removed in a future 
release.

The only problem is that it still enables someone to write source code that 
uses PVALUE - and that source code therefore does not run on Windows if 
winreg.h is included.
But, if PVALUE is documented as being deprecated, we presumably open the 
door to being able to remove it at a future date (without being accused of 
doing something we shouldn't do).
In the meantime it's unlikely that anyone will be inconvenienced.

Cheers,
Rob