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Message-ID: <39495C96.D14912FA@carlthompson.net>
Date: Thu, 15 Jun 2000 15:45:42 -0700
From: Carl Thompson <cet AT carlthompson DOT net>
MIME-Version: 1.0
To: kulack AT us DOT ibm DOT com
Cc: Cygwin List <cygwin AT sourceware DOT cygnus DOT com>
Subject: Re: Can't build a DLL using gcc
References: <852568FF DOT 007476F8 DOT 00 AT D51MTA04 DOT pok DOT ibm DOT com>
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I wrote a message to the list the other day about a much easier way to
create DLLs using Cygwin than using dlltool, dllhelpers and .def files.  You
can see it at

   http://sourceware.cygnus.com/ml/cygwin/2000-06/msg00688.html

This method is not only easier, but also allows you to maintain your symbol
information in one place-- the header files where they belong.  You don't
have to try to keep separate .def files in sync.

Even if you choose to keep using .def files, I believe you can use the newer
method to actually create the DLLs anyway.  This might cure your problem.  I
highly recommend not using .def files and using the technique described in
my message.  It guarantees that the symbols you want to export are exported
correctly.

I know this method works because I use it for non trivial projects.  It's
quite possible the documentation you looked at is outdated or inaccurate.

Hope this helps,
Carl Thompson

kulack AT us DOT ibm DOT com wrote:
> 
> I'm pretty new at Win and gcc development. I've been searching the archives
> for details about this, but have only found hints.
> I've followed the instrutions at
> http://sourceware.cygnus.com/cygwin/cygwin-ug-net/dll.html for building
> DLLs using GCC, but get a STATUS_ACCESS_VIOLATION when I attempt to use it.
> 
> About my only guess is that I'm doing something wrong with the .DEF file.
> Can it get created automatically or should there be a 'SECTIONS' section in
> the .DEF file indicating which type of access (EXECUTE, READ, WRITE) the
> dll should have?
> Not familiar with nm output, but it seems to look ok for the created dll...
> Can anyone teach me to fish? 8-)
> 
> Bash /db2src/test
>  > make libhello.a
> gcc  -g -c -I/sqllib/include libhello.c
> gcc -s -Wl,--base-file,libhello.base -o libhello.dll libhello.o
> -Wl,-e,_mydll_init AT 12
> dlltool --base-file libhello.base --def libhello.def --output-exp
> libhello.exp --dllname libhello.dll
> gcc -s -Wl,--base-file,libhello.base,libhello.exp -o libhello.dll
> libhello.o -Wl,-e,_mydll_init AT 12
> dlltool --base-file libhello.base --def libhello.def --output-exp
> libhello.exp --dllname libhello.dll
> gcc -Wl,libhello.exp -o libhello.dll libhello.o -Wl,-e,_mydll_init AT 12
> dlltool --def libhello.def --dllname libhello.dll --output-lib libhello.a
> cp libhello.dll ..
> rm libhello.o
> 
> Bash /db2src/test
>  > make hello.exe
> gcc  -g -c -I/sqllib/include hello.c
> gcc  -g hello.o -L/db2src/test -lhello
> mv a.exe hello.exe
> 
> Bash /db2src/test
>  > hello
> Hello World
>       0 [main] hello 1127 handle_exceptions: Exception:
> STATUS_ACCESS_VIOLATION
>    9205 [main] hello 1127 stackdump: Dumping stack trace to
> hello.exe.stackdump
> 
> Bash /db2src/test
>  > cat hello.exe.stackdump
> Exception: STATUS_ACCESS_VIOLATION at eip=000055CC
> eax=00000009 ebx=00000000 ecx=0000000C edx=0245FDF4 esi=00000000
> edi=0A041448
> ebp=0245FE74 esp=0245FE58 program=c:\db2src\test\hello.exe
> cs=001B ds=0023 es=0023 fs=003B gs=0000 ss=0023
> Stack trace:
> Frame     Function  Args
> 0245FE74  00401085  (00000009, 0245FEB0, 0245FEA4, 0040106B)
> 0245FEA4  00401085  (00000001, 0A041448, 0A040008, 00000000)
> 0245FF00  610022E5  (7FFDF000, 00000000, 00000018, 80452662)
> 0245FF60  61002735  (00403010, 00000000, 0245FF90, 004011DA)
> 0245FF90  004011E7  (00401060, FFFFFFFF, 80430B27, 00000000)
> 0245FFC0  0040103B  (00000018, 00000000, 7FFDF000, 00000000)
> 0245FFF0  77E87903  (00401000, 00000000, 000000C8, 00000100)
> End of stack trace
> 
> ======= libhello.c
> #include <stdio.h>
> #include <windows.h>
> extern int helloFromDll(int parm);
> 
> int WINAPI
> mydll_init(HANDLE h, DWORD reason, void *foo)
> {
>    return 1;
> }
> 
> int helloFromDll(int parm) {
>    printf("Hello from Dll, parm=%d\n", parm);
>    return parm+1;
> }
> 
> int main(int argc, char **argv) {
>    // This doesn't feel right...
>    // Was forced to add main() in order to get the
>    // instructions for building DLLs at
>    //   http://sourceware.cygnus.com/cygwin/cygwin-ug-net/dll.html
>    // to work correctly, otherwise, linker failed to
>    // find WinMain AT 16 (which I wouldn't have believed it should
>    // require).
> }
> 
> ======= libhello.def
> LIBRARY LIBHELLO
> DESCRIPTION 'LIBHELLO.DLL Testcase'
> EXPORTS
>    helloFromDll
> 
> ======= hello.c
> #include <stdio.h>
> extern int helloFromDll(int parm);
> int main(int argc, char **argv)
> {
>    int         rc;
>    printf("Hello World\n");
>    rc = helloFromDll(9);
>    printf("DLL returned %d\n", rc);
>    return 0;
> }
> 
> --
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