Re: [Mingw-users] how to compile a win32 executable using kernel32.dll ?

[Brian Dessent <brian@xxxxxxxxxxx>]

James Yu wrote:

>      $ make
>      gcc -c hello.c
>      gcc -o hello hello.o -mwindows -lkernel32
>      hello.o:hello.c:(.text+0x79): undefined reference to
>      `_GetProcessId'
>      collect2: ld returned 1 exit status
>      make: *** [all] Error 1
> 
> I have no idea what went wrong and appreciate whoever kind enough to
> show me the way to get out of this mess :-)

The problem has nothing to do with linking to kernel32 per se.  In fact
"-lkernel32" is implicitly given by the specs file for every link, so it
is totally unnecessary to specify it.  You would be hard pressed to
build an executable that *didn't* link to kernel32.dll, in fact, because
it is a critical system component.

No, the problem is that you did not include windows.h which provides the
proper prototype for this function.  Compiling with -Wall would have
caught this with a warning about implicit declaration.  In fact there is
no such function called "GetProcessId" at all in kernel32, there is only
a GetProcessIdA() and GetProcessIdW(), corresponding to the ANSI and
unicode versions of the API.  The header takes care of #defining the
right one for you so that when you use GetProcessId() in your source you
get the desired version.

Brian

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