Re: easy way to tell if "in" package build?

[Joel Klecker <jk@espy.org>]

At 18:51 +0200 1999-10-20, Marcus Brinkmann wrote:
> This is the wrong approach. Creating such dependencies on Debian specific
> hacks in build tools and environment variables looks a lot like "magic".
>
> A hack is not nicer if it is hidden deep in the system. I am not even sure
> if the current Debian policy wrt rpaths is so ideal as most developers
> seem never to question.

I have a suggestion, we should have a `strip-rpath' program.

This is a program from Geoff Keating <geoffk@ozemail.com.au>, it 
needs to be fixed to work on little-endian and 64-bit ELF, before 
it'd meet our needs, but it's a start (I'm sure he's willing to give 
this program a license if someone wants to work on it).

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <elf.h>
#include <stdlib.h>
/* Reads an ELF file, nukes all the RPATH entries. */

int
main(int argc, char **argv)
{
  int fd;
  Elf32_Ehdr ehdr;
  int i;
  Elf32_Phdr phdr;
  Elf32_Dyn *dyns;
  int dynpos;

  if (argc != 2)
  {
    printf ("Usage: %s objectfile\n", argv[0]);
    return 1;
  }

  fd = open(argv[1], O_RDWR);
  if (fd == -1)
  {
    perror ("open");
    return 1;
  }

  if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
  {
    perror ("reading header");
    return 1;
  }

  if (*(unsigned *)ehdr.e_ident != *(const unsigned *)ELFMAG ||
      ehdr.e_ident[EI_CLASS] != ELFCLASS32 ||
      ehdr.e_ident[EI_DATA] != ELFDATA2MSB ||
      ehdr.e_ident[EI_VERSION] != EV_CURRENT)
  {
    fprintf(stderr, "`%s' probably isn't a 32-bit MSB-first ELF file.\n",
	    argv[1]);
    return 1;
  }

  if (ehdr.e_phentsize != sizeof(Elf32_Phdr))
  {
    fprintf(stderr, "section size was read as %d, not %d!\n",
	    ehdr.e_phentsize, sizeof(Elf32_Phdr));
    return 1;
  }

  if (lseek(fd, ehdr.e_phoff, SEEK_SET) == -1)
  {
    perror ("positioning for sections");
    return 1;
  }

  for (i = 0; i < ehdr.e_phnum; i++)
  {
    if (read(fd, &phdr, sizeof(phdr)) != sizeof(phdr))
    {
      perror ("reading section header");
      return 1;
    }
    if (phdr.p_type == PT_DYNAMIC)
      break;
  }
  if (i == ehdr.e_phnum)
    {
      fprintf (stderr, "No dynamic section found.\n");
      return 2;
    }

  dyns = malloc(phdr.p_memsz);
  if (dyns == NULL)
    {
      perror ("allocating memory for dynamic section");
      return 1;
    }
  memset(dyns, 0, phdr.p_memsz);
  if (lseek(fd, phdr.p_offset, SEEK_SET) == -1
      || read(fd, dyns, phdr.p_filesz) != phdr.p_filesz)
    {
      perror ("reading dynamic section");
      return 1;
    }

  dynpos = 0;
  for (i = 0; dyns[i].d_tag != DT_NULL; i++)
    {
      dyns[dynpos] = dyns[i];
      if (dyns[i].d_tag != DT_RPATH)
	dynpos++;
    }
  for (; dynpos < i; dynpos++)
    dyns[dynpos].d_tag = DT_NULL;

  if (lseek(fd, phdr.p_offset, SEEK_SET) == -1
      || write(fd, dyns, phdr.p_filesz) != phdr.p_filesz)
    {
      perror ("writing dynamic section");
      return 1;
    }
  return 0;
}
--
Joel Klecker (aka Espy)                    Debian GNU/Linux Developer
<URL:mailto:jk@espy.org>                 <URL:mailto:espy@debian.org>
<URL:http://web.espy.org/>               <URL:http://www.debian.org/>