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Re: [Mingw-users] mingw and VB
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From: Li W. <li_...@so...> - 2002-12-05 06:02:44
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<blockquote type="cite">How do i make a dll written in c and compiled
in mingw to be interfaced from<br>
Visual Basic ??????? I've already done this but doesnt work:</blockquote>
<br>
Let me see what's wrong here.<br>
<blockquote type="cite">EXPORT unsigned char suma( unsigned char a,
unsigned char b)<br>
{<br>
return a+b;<br>
}<br>
</blockquote>
If you want Visual Basic to call this function, you must use stdcall,
not ccall, so your <br>
fuction must be declared like this:<br>
<br>
__stdcall unsigned char suma( unsigned char a, unsigned char b)<br>
<br>
Or, if you have include windows.h, you can use <br>
WINAPI ,PASCAL . . . instead of __stdcall. Like this:<br>
<br>
WINAPI unsigned char suma( unsigned char a, unsigned char b)<br>
<blockquote type="cite">#ifdef BUILD_DLL<br>
// the dll exports<br>
#define EXPORT __declspec(dllexport)<br>
#else<br>
// the exe imports<br>
#define EXPORT __declspec(dllimport)<br>
#endif<br>
<br>
EXPORT unsigned char suma ( unsigned char a, unsigned char b);</blockquote>
Never use __declspec(dllexport) if you want it can be used anywhere.<br>
then why? <br>
1. your must rebuild the caller application every time when the dll be
changed.<br>
2. if you use __declspec(dllexport) and use stdcall, VB can not find
the entry point <br>
of the function, because the export function will be name as something <br>
like suma@8 by compiler. except ,you declare the function name as <br>
suma@8 in VB,would you like this? and you know if do not use stdcall
,VB can find<br>
the entry point , but the paramerter check will failed. <br>
<br>
So make a def file instead of use __declspec(dllexport) . like this:<br>
suma.def<br>
<br>
LIBRARY "suma"<br>
DESCRIPTION 'The Suma Dynamic Link Library'<br>
EXPORTS<br>
suma @1<br>
<br>
Then compile use:<br>
gcc -shared -o suma.dll suma.c suma.def<br>
<br>
Sorry for my poor english.<br>
<br>
<br>
<em><b><i><font><span>Best Regards<br>
</span></font></i></b></em>-------------------------------------------------------<br>
Li Wenhao<br>
Programmer, My friend like call me "Mouse"<br>
So you can.<br>
-------------------------------------------------------<br>
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