10.29. Creating a Multiarch Wrapper

The Multiarch Wrapper is used to wrap certain binaries that have hardcoded paths to libraries or are architecture specific.

10.29.1. Installation of The Multiarch Wrapper

Create the source file:

cat > multiarch_wrapper.c << "EOF"
#define _GNU_SOURCE

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#ifndef DEF_SUFFIX
#  define DEF_SUFFIX "64"

int main(int argc, char **argv)
  char *filename;
  char *suffix;

  if(!(suffix = getenv("USE_ARCH")))
    if(!(suffix = getenv("BUILDENV")))
      suffix = DEF_SUFFIX;

  if (asprintf(&filename, "%s-%s", argv[0], suffix) < 0) {
    return -1;

  int status = EXIT_FAILURE;
  pid_t pid = fork();

  if (pid == 0) {
    execvp(filename, argv);
  } else if (pid < 0) {
  } else {
    if (waitpid(pid, &status, 0) != pid) {
      status = EXIT_FAILURE;
    } else {
      status = WEXITSTATUS(status);


  return status;


Compile and Install the Multiarch Wrapper:

gcc ${BUILD64} multiarch_wrapper.c -o /usr/bin/multiarch_wrapper

This multiarch wrapper is going to be used later on in the book with Perl. It will also be very useful outside of the base CLFS system.

Create a testcase:

echo 'echo "32bit Version"' > test-32
echo 'echo "64bit Version"' > test-64
chmod -v 755 test-32 test-64
ln -sv /usr/bin/multiarch_wrapper test

Test the wrapper:

USE_ARCH=32 ./test
USE_ARCH=64 ./test

The output of the above command should be:

32bit Version
64bit Version

Remove the testcase source, binaries, and link:

rm -v multiarch_wrapper.c test{,-32,-64}

10.29.2. Contents of The Multiarch Wrapper

Installed programs: multiarch_wrapper

Short Descriptions


Will execute a different program based on the USE_ARCH variable. The USE_ARCH variable will be the suffix of the executed program.