Visual Basic and GCC

["Giandomenico De Sanctis" <mc4420 at mclink dot it>]

For who is interested using GNU C-Win32 with Visual Basic, I follow this
steps:
Note: I installed the Minimal GCC-Win32, then the note is referred at this
package;
also, the installation is on Win 95, I not have any experience with Win NT

1) compiling a C DLL, callable by VB 4:
 1.1- prepare the .DEF file with the functions exported by the library, for
example
         EXPORTS
         func1
         func2
 1.2- execute the dlltool utility ('myl' is the name of library in the
example):
dlltool --def myl.def --output-exp myl.exp --output-lib myl.a --dllname
myl.dll
 with this you obtained the .EXP file for use in successive step, and the
.A file
 for using the DLL in others C/C++ programs
 1.3- compile/link the DLL with:
gcc -o myl.dll myl.c myl.exp -dll -mrtd  -windows -mpentium
 use '-windows' only if the DLL call any Win functions; '-mpentium'
optimize the
 code for Pentium, use '-m386' or '-m486' for other processors; '-mrtd' is
essential,
 because force the use of the STDCALL calling convention, that is also used
by VB 4
 With this step you obtain the MYL.DLL.
 1.4- if you want debug the DLL, only by a C calling test program, not by
VB, add the
 '-ggdb3' parameter; after, to debug execute
gdb testp.exe
 assuming 'testp.exe' is the test C program
 1.5- remember that VB 4 integer type correspond to short C type (2 bytes)
in Win32,
 because the integer C type is 4-bytes long

2) obtaining a link definition file to use an existing DLL with a GCC
program/DLL:
 2.1- if you have the MS Visual C .LIB file for the library, prepare the
list
 of exported functions with:
nm exil.lib >exil.def
 (of course, 'exil' is the existing library)
 manually edit exil.def, leaving only the names of exported functions,
without
 leading underscore, but leaving the trailing @xx if any
 2.2- if you not have the .LIB, in explorer right click on the DLL file,
 and choose preview; then, manually (the clipboard is not active !)
 annotate the names of functions, and prepare the .DEF file
 2.3- execute dlltool:
dlltool -k --def exil.def --output-lib exil.a --dllname exil.dll
 the '-k' option eliminate the trailing @xx from function names in the .A
files,
 and is necessary when using the STDCALL convention (then, always when
compiling
 DLL for VB).

<GiDeSa> 

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