From: David Garamond <lists@...6.isreserved.com>
Date: 2004-03-21T20:48:03+09:00
Subject: Re: Can $LOAD_PATH be relative?

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1-2 weeks ago I asked the same question about a Linux binary Ruby 
installation that can be installed anywhere in users' home directory 
(without the user building Ruby himself). To accomplish this, the 
following is needed:

1) build Ruby with --enable-load-relative (you must patch Ruby with +- 
100-line patch from Nobu; sorry I couldn't search ruby-talk.org at the 
moment but it's around the first week of March 2004) which will make 
$LOAD_PATH relative;

2) either:

a) make a small wrapper for ruby executable, which makes Ruby find its 
shared libraries in "../lib" instead of only in /lib, /usr/lib, and 
other paths specified in /etc/ld.so.conf; (I'm attaching the small 
wrapper I wrote, which again was kindly revised by Nobu);

b) build a static version of Ruby (--disable-shared in configure 
option), which will then depend only on basic shared libraries (like glibc).

After that, you can just bundle the resulting Ruby installation.

Hope that helps,
-- 
dave


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#include <stdio.h>
#include <errno.h>

/* 
 * wrapper.c
 *
 * This is a simple executable wrapper that inserts "../lib" into
 * LD_LIBRARY_PATH so that the executable can find shared libraries relative
 * to its position. Works only on Linux (or other OS which supports
 * /proc/self/exe).
 *
 * To use this wrapper, first compile this file using: gcc -o wrapper
 * wrapper.c. Then, suppose you want to wrap the Ruby executable in
 * /home/dave/usr/bin/ruby. Rename the original executable to
 * /home/dave/usr/bin/ruby.real (or with whatever suffix; see
 * WRAPEE_SUFIX below). Then copy the wrapper binary to
 * /home/dave/usr/bin/ruby. This means that when you invoke the executable,
 * Ruby will find its libraries in /home/dave/usr/lib/ first instead of the
 * usual /usr/lib/.
 *
 */

#define MAX_PATH_LENGTH                       1024
#define WRAPEE_SUFFIX                         ".real"

int main(int argc, char *argv[]) {
   static char binpath[MAX_PATH_LENGTH+sizeof(WRAPEE_SUFFIX)+1];
   static char libpath[MAX_PATH_LENGTH+sizeof("../lib")+1];
   char *p;
   char *env;

   if (readlink("/proc/self/exe", binpath, MAX_PATH_LENGTH) == -1) {
     fprintf(stderr, "readlink() failed: %s (maybe /proc is not "
                     "mounted or restricted?)\n", strerror(errno));
     exit(1);
   }

   strcpy(libpath, binpath);
   p = libpath + strlen(libpath);
   while (p >= libpath) {
     if (*p == '/') {
       strcpy(p, "/../lib");
       break;
     }
     p--;
   }

   p = (char *)getenv("LD_LIBRARY_PATH");
   if ((env = (char *)malloc(MAX_PATH_LENGTH+1+1+
                             (p==NULL ? 0 : strlen(p)))) == NULL) {
     fprintf(stderr, "malloc() failed: %s\n", strerror(errno));
     exit(1);
   }
   strcat(env, "LD_LIBRARY_PATH=");
   if (p != NULL) {
     strcpy(env, p);
     strcat(env, ":");
   }
   strcat(env, libpath);
   if (putenv(env) == -1) {
     fprintf(stderr, "putenv() failed: %s\n", strerror(errno));
     exit(1);
   }

   strcat(binpath, ".real");
   execv(binpath, argv);
   fprintf(stderr, "Can't execute wrapee: %s\n", strerror(errno));
   exit(1);
}

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