Hello,
I am using Gambit4b12 to write a plugin for a C++ program. I've done some tests and had some success although right now I'm having some problems when using it in a DLL.
First I would like to suggest a small improvement for the C code generation. Maybe I'm missing a switch to pass to gsc but every time I generate the C code I have to add extern "C" {} wrapper around each file after I move all the #include outside that block. I also noticed that gambit.c doesn't have a extern "C" wrapper and I had to add it. I think it would be simple to automatically add: #ifdef __cplusplus extern "C" {} #endif wrapper when generating the code. I don't know how easy would be to extract the includes in c-declare outside that wrapper but it would be nice to avoid manually editing the file.
The problem I'm having right now is that the code which runs fine in a single standalone program crashes when is called in a loaded DLL. I think it must be something in the way the initialization has to be done but the documentation is not too clear.
If someone would be able to give me a hint I would appreciate it. I am using mingw on Windows and I get this error:
Program received signal SIGSEGV, Segmentation fault. 0x1012a67f in ___CHARSTRING_to_UCS2STRING () from c:\Gambitc_project\finalePlugin\testing\test.dll (gdb) bt #0 0x1012a67f in ___CHARSTRING_to_UCS2STRING () from c:\Gambitc_project\finalePlugin\testing\test.dll #1 0x00000000 in ?? () from #2 0x0022fe68 in ?? () #3 0x101248b1 in ___alloc_mem () from c:\Gambitc_project\finalePlugin\testing\test.dll Previous frame inner to this frame (corrupt stack?)
The code is bellow.
Thank you, Dan Hristodorescu.
- Main program: #include <windows.h> #include <stdio.h> #include "note.h"
typedef void (*EntryPointfuncPtr)(EXNOTE*); EntryPointfuncPtr callEntryPoint; HINSTANCE library;
int main(int argc,char **argv) { library = LoadLibrary("test.dll"); // Check to see if the library was loaded successfully if (library == 0) { printf("Couldn't load the DLL"); exit(1); } EXNOTE* note1 = new EXNOTE(); note1->tcd=1; note1->alteration=1; note1->noteID=1; note1->flag=1; printf("Address=0x%X\n", note1); callEntryPoint = (EntryPointfuncPtr)GetProcAddress(library,"_Z10entryPointP6EXNOTE"); (*callEntryPoint)(note1); printf("Note->tcd= %d\n", note1->tcd); printf("Note->alteration= %d\n", note1->alteration); printf("Note->noteID= %d\n", note1->noteID); printf("Note->flag= %d\n", note1->flag); delete note1; }
DLL code: #include <windows.h> #include <stdio.h> #include "note.h"
extern "C" void pluginEntry(EXNOTE*);
#define ___VERSION 40062 #include "gambit.h"
#define SCHEME_LIBRARY_LINKER ____20_testscm__
___BEGIN_C_LINKAGE extern ___mod_or_lnk SCHEME_LIBRARY_LINKER (___global_state_struct*); ___END_C_LINKAGE
CALLBACK void entryPoint(EXNOTE* note1) { ___setup_params_struct setup_params; ___setup_params_reset (&setup_params); setup_params.version = ___VERSION; setup_params.linker = SCHEME_LIBRARY_LINKER; ___setup (&setup_params);
pluginEntry(note1);
___cleanup (); }
note.h file: #ifndef _NOTE_H_ #define _NOTE_H_
typedef short twobyte; typedef unsigned long ufourbyte; typedef ufourbyte FLAG_32;
class EXNOTE { public: twobyte tcd; twobyte alteration; twobyte noteID; FLAG_32 flag;
EXNOTE() : tcd(0), alteration(0), noteID(0), flag(0) {} ~EXNOTE() {} }; #endif
Scheme code:
(c-declare " #include "note.h" ")
(c-define-type twobyte short) (c-define-type ufourbyte unsigned-long) (c-define-type FLAG_32 ufourbyte)
;; ;;;; EXNOTE ;;;
(c-define-type EXNOTE* (pointer "EXNOTE"))
(define EXNOTE-tcd (c-lambda (EXNOTE*) twobyte "___result = ___arg1->tcd;"))
(define EXNOTE-tcd-set! (c-lambda (EXNOTE* twobyte) void "___arg1->tcd = ___arg2;"))
(define transpose-note (lambda (note step) (EXNOTE-tcd-set! note (+ (EXNOTE-tcd note) step))))
(c-define (pluginEntry x) (EXNOTE*) void "pluginEntry" "extern" (write x) (newline) (transpose-note x 3))