Example of the dll by the cygwin

README.md

Example of the dll by the cygwin

What's this?

This is the most simple code for defining dll and using dll. You can do to confirm it as below:

# build and test code
make test

License

Copyright (c) 2016 Koichi OKADA. All rights reserves.

This codes distributed under the MIT license.

References

• LoadLibrary function
• FreeLibrary function
• GetProcAddress function
• MessageBox function

call.c

#include <windef.h>
#include <winbase.h>
#include <stdio.h>
#include <stdlib.h>

main(int argc, char *argv[])
{
  int retcode = EXIT_FAILURE;
  
  if (argc != 5) {
    printf("Usage: %s dll func text caption\n", argv[0]);
    return retcode;
  }
  
  HMODULE dll = LoadLibrary(argv[1]);
  printf("%p\n", dll);
  if (dll) {
    FARPROC fnc = GetProcAddress(dll, argv[2]);
    printf("%p\n", fnc);
    if (fnc) {
      ((int (*)(HWND, LPCTSTR, LPCTSTR, UINT)) fnc)(0, argv[3], argv[4], 0);
      retcode = EXIT_SUCCESS;
    }
    FreeLibrary(dll);
  }
  
  return retcode;
}

libmsg.c

#include <windef.h>
#include <winuser.h>

int msg(HWND hWnd, LPCTSTR lpText, LPCTSTR lpCaption, UINT uType)
{
  return MessageBox(hWnd, lpText, lpCaption, uType);
}

Makefile

all: call libmsg.so

call: call.c
	$(CC) $< -o $@
libmsg.so: libmsg.c
	$(CC) -shared $< -o $@
clean:
	-$(RM) -v call libmsg.so
test: all
	./call user32.dll MessageBoxA "MessageBoxA()" user32.dll
	./call libmsg.so msg "msg()" libmsg.so