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From: Sebastian Miele <smiele AT ps DOT uni-sb DOT de>
Subject: loading cygwin1.dll at runtime
Date: 16 May 2003 23:14:48 +0200
Lines: 62
Message-ID: <e0d6iiy4on.fsf@wallaby.ps.uni-sb.de>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

Hi,

I want to add the following feature to an application compiled with
-mno-cygwin:

  Every time the application is about to make a system call with a
  pathname as argument the application should convert the (possibly
  cygwin/unix) path to the corresponding windows path using
  cygwin_conv_to_full_win32_path provided by cygwin1.dll, but only if
  cygwin1.dll is present on the current host.

In order to do that I need to link cygwin1.dll at runtime and get a
pointer to cygwin_conv_to_full_win32_path.  I tried to do this by just
using LoadLibrary/GetProcAddress/FreeLibrary provided by Windows.
However, the application crashes.  Gdb tells:

  Program received signal SIGSEGV, Segmentation fault.
  0x61051931 in getpass ()
  (gdb) bt
  #0  0x61051931 in getpass ()
  #1  0x6104f268 in getpass ()
  #2  0x61056629 in cygwin_conv_to_full_win32_path ()
  #3  0x00401423 in main (argc=2, argv=0x3f24e8) at t.c:21

Maybe I am missing a call to an initialization routine.  Here is a
complete compilable example:

  #include <stdio.h>
  #include <Windows.h>
  
  typedef void (*conv_fun_t) (const char*, char*);
  
  int main(int argc, char* argv[])
  {
    if (argc!=2) { fprintf(stderr,"fucking arguments\n"); return 1; }
    const char* input_path= argv[1];
  
    HMODULE libcygwin;
    conv_fun_t cygwin_conv_to_full_win32_path;
    libcygwin= LoadLibrary("cygwin1.dll");
    if (libcygwin==NULL) { fprintf(stderr,"fuck1\n"); return 1; }
    cygwin_conv_to_full_win32_path=
      (conv_fun_t)(GetProcAddress(libcygwin,"cygwin_conv_to_full_win32_path"));
    if (cygwin_conv_to_full_win32_path==NULL) { fprintf(stderr,"fuck2\n"); return 1; };
  
    char *windows_path= malloc(sizeof(char)*(MAX_PATH+1));
    fprintf(stderr,"calling cygwin-conv on '%s'\n", input_path);
    cygwin_conv_to_full_win32_path(input_path,windows_path);
    printf(windows_path);
    
    FreeLibrary(libcygwin);
    return 0;
  }

I compiled the program with

  gcc -mno-cygwin -g -o t t.c

Any ideas?

Thank's in advance & Best wishes
Sebastian


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