Question

I’m trying to create a PHP extension for Windows, using the Visual Studio Express. I started the extension from scratch and had just test.cpp file, where I wrote some code. Although the code compiled and worked well, during compilation it produced several warnings, I’d rather get rid of.

I reduced the file to a single line, which reproduces those warnings:

#include "php.h"

Building such an empty DLL I get:

>Compiling...
>test.cpp
>C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\stdio.h(620) : warning C4273: 'getwchar' : inconsistent dll linkage
>        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\stdio.h(435) : see previous definition of 'getwchar'
>C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\stdio.h(622) : warning C4273: 'putwchar' : inconsistent dll linkage
>        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\stdio.h(437) : see previous definition of 'putwchar'

What is the proper way to fix these two warnings?

I’ve tried to investigate the issue, and checked if I forgot some preprocessor directive. But I couldn’t find anything applicable to influence that stdio.h properly.

Here is the list of my preprocessor directives, as set up in the project configuration:

WIN32
NDEBUG
_WINDOWS
_USRDLL
TEST_EXPORTS
PHP_WIN32
ZEND_WIN32
ZTS=1
ZEND_DEBUG=0

Inherited values:
_WINDLL
_UNICODE
UNICODE

It looks pretty same as other PHP projects have. I’ve also studied the stdio.h, but haven’t found appropriate preprocessor directives to set.

So, the main question is divided into smaller questions:

1. What is the PHP authors’ intent – should I have those
   getwchar() and putwchar() functions imported or declared inline? stdio.h tries to do that simultaneously.
2. Have I missed some preprocessor directive to set?
3. Do I have to include some win32-specific header files from PHP sources?

Answer 1

Eventually I managed to find the issue – that was the .cpp extension, which caused the file to be compiled as C++, while the PHP is written in plain C.

The simplest solution is just to rename file to have .c extension. And, of course, write the source in C.