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Date: Mon, 14 Feb 2000 06:00:21 -0800
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To: freebsd-hackers@freebsd.org
Subject: Help me understand dlopen/dlsy
From: "Pradesh Chanderpaul" <archiver@db.geocrawler.com>
Reply-To: "Pradesh Chanderpaul" <pradesh.chanderpaul@iname.com>
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This message was sent from Geocrawler.com by "Pradesh Chanderpaul" <pradesh.chanderpaul@iname.com>
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Hello All

 I know that this question is more suited to the general
 questions mailing group, but I tried, and failed to obtain
 a response. So could someone please provide guidance with this
 topic. I have searched the mailing lists, man pages and the
 net at large without getting a satisfactory understanding.

 Consider the following scenario.

 I need to compile a program consisting of two source files
 and a makefile

 file1.c
 -------
 #include <stdio.h>
 #include <stdlib.h>
 #include <dlfcn.h>

 int main() {
 void *handle;
 void (*myhellofunc)(void);
 char *c;

      handle = dlopen(NULL, 1);
      c = dlerror();

      if (c) abort_with_error(c);

      myhellofunc = dlsym(handle, "_helloworld");
      c = dlerror();

      if(c) abort_with_error(c);

      myhellofunc();
      dlclose(handle);
 }

 file2.c
 -------
 #include <stdio.h>
 void helloworld(void) {
      printf(" Hello cruel worldn");
 }

 Makefile
 --------
 file1.o : file1.c
         gcc -fPIC -c file1.c

 file1.o : file1.c
         gcc -fPIC -c file1.c

 fileit : file1.o file2.o
         cc -export-dynamic -o fileit file1.o file2.o


 The two source files will be linked into a single executable,
 using GCC running on FreeBSD 3.2-RELEASE.

 Q1 : Are my flags sufficient to compile the individual
      source files?
 Q2 : What flags are required to link the object files into
      the single executable?
 Q3 : Is there anything else I should be wary of?

 I have tried various options (like using -rdynamic and -shared
 but to no avail. dlerror() reports an undefined symbol for
 _helloworld from calling dlsym.

 This issue has been "bugging" me for weeks now, so I need to
 try and get it sorted out. Please assist if you can.

 Thanking you in advance.
 Pradesh Chanderpaul

Geocrawler.com - The Knowledge Archive


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