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Date: Fri, 17 Sep 2004 08:21:57 -0700
From: Lester Ingber <ingber AT ingber DOT com>
To: cygwin AT cygwin DOT com, mingw-users AT lists DOT sourceforge DOT net
Subject: file I/O and calling executables from a DLL?
Message-ID: <20040917152157.GA1568@ingber.com>
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I'm having problems executing file I/O and calling executables from
a DLL?  I know this sounds simple, and this works fine under Excel,
but I'm having problems doing this with TradeStation.

Is there anything I should know about changes in paths, root directories,
etc., that can occur under different applications?

I have modified a simple code to prepare a DLL from a fairly well-known
tool, dllhelpers,
http://www.xraylith.wisc.edu/~khan/software/gnu-win32/dllhelpers.html
and I have produced an equally good DLL using a Makefile enclosed.
I've just added a call to another independent executable.  This works
just fine (using either the more standard dllhelper way or using my
own Makefile) under Excel using the dllhelpers-prepared dlltest.xls.

Here's some simple code I prepared to explain what I've done.  I'm using
*all* the most current Curr downloads via setup.exe from cygwin.com.

Makefile for cdll.c:
    ------------8<------------ top cut -> bottom ------------->8------------
DLL_OPTION=-mrtd  # I found this necessary for DLLs to work
CYGWIN_OPTION=-mno-cygwin $(DLL_OPTION)

CC = gcc
CDEBUGFLAGS = -g -O -Wall
CFLAGS = $(CDEBUGFLAGS) $(CYGWIN_OPTION)

LDFLAGS = $(CYGWIN_OPTION)

obj_libs = cdll.o
dllmodule = cdll
dependency_libs = -lm
all:
        $(CC) $(CFLAGS) -c -o ${obj_libs} cdll.c
        $(CC) $(CFLAGS) -mrtd -shared -o ${dllmodule}.dll \
        -Wl,--out-implib=${dllmodule}.lib \
        -Wl,--compat-implib \
        -Wl,--add-stdcall-alias \
        -Wl,--enable-stdcall-fixup \
        -Wl,--enable-auto-import \
        -Wl,--enable-auto-image-base \
        -Wl,--whole-archive ${obj_libs} \
        -Wl,--export-all-symbols \
        -Wl,--output-def=${dllmodule}.def \
        -Wl,--no-whole-archive ${dependency_libs}
    ------------8<------------ bottom cut <- top ------------->8------------

cdll.c  (In Tradestation, you have to change double->float):
    ------------8<------------ top cut -> bottom ------------->8------------
#include <errno.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

double dll_double_square (double d);

double
dll_double_square (double d)
{
  char trd_comm[200];
  FILE *ptr_comm;

  /* I tried this with a system() call, but it still doesn't work when
     dll_double_square is called in TradeStation */
  sprintf (trd_comm, "run_trd.exe");
  ptr_comm = popen (trd_comm, "r");
  pclose (ptr_comm);

  return d * d;
}
    ------------8<------------ bottom cut <- top ------------->8------------

Makefile for trd.c:
    ------------8<------------ top cut -> bottom ------------->8------------
CYGWIN_OPTION=-mno-cygwin

CC = gcc
CDEBUGFLAGS = -g -O -Wall
CFLAGS = $(CDEBUGFLAGS) $(CYGWIN_OPTION)

LDFLAGS = $(CYGWIN_OPTION)

obj_libs = trd.o
all: $(obj_libs)
        @$(CC) $(LDFLAGS) -o run_trd.exe $(obj_libs) -lm
    ------------8<------------ bottom cut <- top ------------->8------------

trd.c:
    ------------8<------------ top cut -> bottom ------------->8------------
#include <errno.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main ();

int
main ()
{
  char trd_comm[50];
  FILE *ptr_comm;

  sprintf (trd_comm, "mkdir ..\\IO\\%s", "test_dir");
  ptr_comm = popen (trd_comm, "r");
  pclose (ptr_comm);

  printf ("mkdir test_dir\n");

  return 0;
}
    ------------8<------------ bottom cut <- top ------------->8------------

I have the same non-results in TradeStation, but OK results in Excel,
if I simply create the test_dir within cdll.c, e.g., *not* calling any
other executable.

In TradeStation, the code returns just fine, and goes on to do other
stuff, but the commands I cite just are not being executed?

I also tried including explicit paths, e.g., prefacing the executable
and file with c:\cygwin\..., and not even using any relative paths like
"..", but with no positive effect.

Thanks.

Lester



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