To: cygwin AT cygwin DOT com
From: "Antti Karanta" <antti DOT karanta AT napa DOT fi>
Subject:  Loading cygwin1.dll from a windows app
Date:  Mon, 26 Mar 2007 15:20:00 +0300
Lines: 198
Message-ID:  <op.tpspvmdslo37ie@nw17.napa.fi>
Mime-Version:  1.0
Content-Type:  text/plain; format=flowed; delsp=yes; charset=iso-8859-15
Content-Transfer-Encoding:  Quoted-Printable
User-Agent: Opera Mail/9.10 (Win32)
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com


                                   Hi!

   I am trying to load the cygwin1.dll from a windows c app, but am having=
=20=20
difficulties. I did a fair amount of googling
and found stuff concerning this, e.g.

http://cygwin.com/faq/faq.programming.html#faq.programming.msvs-mingw
http://sources.redhat.com/cgi-bin/cvsweb.cgi/winsup/cygwin/how-cygtls-works=
.txt?rev=3D1.1&content-type=3Dtext/x-cvsweb-markup&cvsroot=3Duberbaum

   I also read

http://sources.redhat.com/cgi-bin/cvsweb.cgi/winsup/testsuite/winsup.api/cy=
gload.cc?rev=3D1.1&content-type=3Dtext/x-cvsweb-markup&cvsroot=3Duberbaum
http://sources.redhat.com/cgi-bin/cvsweb.cgi/winsup/testsuite/winsup.api/cy=
gload.h?rev=3D1.2&content-type=3Dtext/x-cvsweb-markup&cvsroot=3Duberbaum

   but I still can't make it work. =3D (


   More detail:

   I am trying to load cygwin1.dll to invoke the cygwin path conversion=20=
=20
functions (to make my program easier to use from cygwin shell).
I do this to convert the command line params denoting paths or files to=20=
=20
windows format that the java virtual machine I am launching expects.
The jvm is also the reason why I can't compile my app as cygwin app - the=
=20=20
java jni (java native interface) headers contain windows specific
stuff that makes gcc fail, unless -mno-cygwin is used. BTW, now that Java=
=20=20
is gpl are there any plans to make a cygwin version of Java? That would
naturally solve my problem, too, as I could compile my app as a cygwin app=
=20=20
and wouldn't even need to call the path conversion funcs.

   The example about loading cygwin1.dll in a win app was in c++, but my=20=
=20
code is c. Also, I am not familiar w/ assembler
programming, so I suspect it is one of these my error lies.


   Anyhow, here's what I am doing now:

   typedef void ( *cygwin_initfunc_type)() ;
   typedef void ( *cygwin_conversionfunc_type)( const char*, char*) ;

   static cygwin_initfunc_type       cygwin_initfunc            =3D NULL ;
   static cygwin_conversionfunc_type cygwin_posix2win_path      =3D NULL ;
   static cygwin_conversionfunc_type cygwin_posix2win_path_list =3D NULL ;

static int mainRval ; // I declared this outside the main func 'cause I'm=
=20=20
a little unsure of what the stack manipulation
                       // does
// 2**15
#define PAD_SIZE 32768
typedef struct {
   void* backup ;
   void* stackbase ;
   void* end ;
   byte padding[ PAD_SIZE ] ;
} CygPadding ;

static CygPadding *g_pad ;

// ...
// in main:

   CygPadding pad ;
   void* sbase ;

   g_pad =3D &pad ;
   pad.end =3D pad.padding + PAD_SIZE ;

   #if defined( __GNUC__ )
   __asm__ (
     "movl %%fs:4, %0"
     :"=3Dr"( sbase )
     ) ;
   #else
   __asm {
     mov eax, fs:[ 4 ]
     mov sbase, eax
   }
   #endif
   g_pad->stackbase =3D sbase ;

   if ( g_pad->stackbase - g_pad->end ) {
     size_t delta =3D g_pad->stackbase - g_pad->end ;
     g_pad->backup =3D malloc( delta ) ;
     if( !( g_pad->backup) ) {
       fprintf( stderr, "error: out of mem when copying stack state\n" ) ;
       return -1 ;
     }
     memcpy( g_pad->backup, g_pad->end, delta ) ;
   }

   mainRval =3D rest_of_main( argc, argv ) ;

   // clean up the stack (is it necessary? we are exiting the program=20=20
anyway...)
   if ( g_pad->stackbase - g_pad->end ) {
     size_t delta =3D g_pad->stackbase - g_pad->end ;
     memcpy( g_pad->end, g_pad->backup, delta ) ;
     free( g_pad->backup ) ;
   }


   // ...
   // in rest_of_main invoked above:

   char *classpath_dyn  =3D NULL,
        *scriptpath_dyn =3D NULL ;
   HINSTANCE cygwinDllHandle =3D LoadLibrary("cygwin1.dll") ;

   if ( cygwinDllHandle ) { // note that not finding cygwin1.dll is not an=
=20=20
error - if it's not there, we are in a "normal" win cmd shell and continue=
=20=20
w/out the path conversions

     cygwin_initfunc            =3D (cygwin_initfunc_type)=20=20=20=20=20=
=20=20
GetProcAddress( cygwinDllHandle, "cygwin_dll_init"                 ) ;
     cygwin_posix2win_path      =3D=20=20
(cygwin_conversionfunc_type)GetProcAddress( cygwinDllHandle,=20=20
"cygwin_conv_to_win32_path"       ) ;
     cygwin_posix2win_path_list =3D=20=20
(cygwin_conversionfunc_type)GetProcAddress( cygwinDllHandle,=20=20
"cygwin_posix_to_win32_path_list" ) ;

     if ( !cygwin_initfunc || !cygwin_posix2win_path ||=20=20
!cygwin_posix2win_path_list ) {
       fprintf( stderr, "strange bug: could not find appropriate init and=
=20=20
conversion functions inside cygwin1.dll\n" ) ;
       goto end ;
     }
     cygwin_initfunc() ;
   } // if cygwin1.dll is not found, just carry on. It means we're not=20=
=20
inside cygwin shell and don't need to care about cygwin path conversions


   Something bad evidently happens as stuff written to stdout by the jvm=20=
=20
goes nowhere - it does not appear on screen.

   Any ideas?


   You can find the full source at:

   https://svn.codehaus.org/groovy/trunk/groovy/modules/native_launcher/sou=
rce/groovy.c


         -Antti-


   Ps. My environment is win xp sp 2 and
$ uname -a
CYGWIN_NT-5.1 NW17 1.5.23(0.156/4/2) 2006-12-19 10:52 i686 Cygwin


--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/