Re: Question regarding building dlls

["Charles S. Wilson" <cwilson at ece dot gatech dot edu>]

Take a look at 

  http://cygutils.netpedia.net/dllhelpers-0.2.6.tar.gz

based on earlier work by Mumit Khan, but updated to reflect the
capabilities of current gcc/binutils.  Contains examples of building
dll's in C, C++, and Fortan.

--Chuck


Greg Clinton wrote:
> 
> I'm having trouble with dll's that I build with gcc and dlltool. Any
> time I try do do anything useful within a dll function, such as call
> new or call any Win32 API, I get an access violation. Does anyone see
> what I'm doing wrong? Below I provide mydll.cpp, mydll.def, myprog.c,
> and build.bat. I'm using gcc version 2.95.2-5 19991024 (cygwin experimental)
> Ultimately I intend to build an inproc COM server.
> 
> Thanks in advance for your help.
> Greg Clinton
> greg.clinton@wonderware.com
> 
> ------------------------------mydll.cpp------------------------------
> #include <windows.h>
> 
> int main()
>   {
>   return 0;
>   }
> 
> extern "C" int WINAPI
> mydll_init(HANDLE h, DWORD reason, void *foo)
> {
>   return 1;
> }
> 
> 
> extern "C" int WINAPI
> calc()
> {
>   int *p = new int;
>   delete p;
>   return 34;
> }
> 
> ------------------------------mydll.def------------------------------
> LIBRARY
> 
> EXPORTS
>   mydll_init
>   calc
> 
> --------------------------------myprog.c------------------------------
> #include <windows.h>
> 
> typedef int (WINAPI *CalcProc)();
> 
> int main()
>   {
>   int i;
>   HMODULE hModule = LoadLibrary("mydll.dll");
>   CalcProc calc = (CalcProc) GetProcAddress(hModule, "calc");
>   i = calc();
>   FreeLibrary(hModule);
>   return i;
>   }
> 
> ------------------------------build.bat------------------------------
> set path=%path%;c:\cygwin\bin
> set include=c:\cygwin\usr\include;
> gcc -c myprog.c
> gcc -c mydll.cpp
> gcc -s -Wl,--base-file,mydll.base -o mydll.dll mydll.o -Wl,-e,_mydll_init@12
> 
> dlltool --base-file mydll.base --def mydll.def --output-exp mydll.exp
> --dllname mydll.dll
> gcc -s -Wl,--base-file,mydll.base,mydll.exp -o mydll.dll mydll.o
> -Wl,-e,_mydll_init@12
> dlltool --base-file mydll.base --def mydll.def --output-exp mydll.exp
> --dllname mydll.dll
> gcc -Wl,mydll.exp -o mydll.dll mydll.o -Wl,-e,_mydll_init@12
> gcc -o myprog myprog.o
> myprog.exe
> 
> -----------------------myprog.exe.stackdump-----------------------------
> Exception: STATUS_ACCESS_VIOLATION at eip=6E677963
> eax=6E677963 ebx=140D1074 ecx=0240FF08 edx=77FCD348 esi=6107C0E8
> edi=00000000
> ebp=0240F75C esp=0240FBF8 program=C:\temp\MyDll\myprog.exe
> cs=001B ds=0023 es=0023 fs=003B gs=0000 ss=0023
> Stack trace:
> Frame     Function  Args
> 0240F75C  6E677963  (00000000, 00000000, 00000000, 00000000)
> 0240FC04  6E677963  (140D1074, 6107C0E8, 00000000, 0240FCF4)
> 0240FD24  140D1209  (00000004, 00000000, 00000000, 00000004)
> 0240FD54  140D1084  (00000004, 0240FDA0, 61040551, 00000004)
> 0240FD84  00401091  (00000001, 0A011218, 0A010008, FFFFFFFE)
> 0240FF10  610038AD  (00000000, 03EEDEE4, 8046A640, 87F00280)
> 0240FF40  61003A8D  (00401054, 03EEDEE4, 8340BAC0, 8049F5BE)
> 0240FF60  61003ACC  (00000000, 00000000, 8340BC50, 00000005)
> 0240FF90  004010FF  (00401054, FFFFFFFF, 80430B27, 00000000)
> 0240FFC0  0040103D  (03EEDEE4, 0000064A, 7FFDF000, 03EEDC7C)
> 0240FFF0  77E87903  (00401000, 00000000, 000000C8, 00000100)
> End of stack trace
> 
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