Re: "Fixing" new ld(1) DT_NEEDED handling

[Christian Groessler <chris%groessler.org@localhost>]

On 10/14/13 08:45, Martin Husemann wrote:
> You guys have lost me - let me try to summarize and please correct me:
>
> AFAIU the solaris linker behaviour (as quoted by uwe) is the only sane
> one.
>
> With that (Solaris ld) behaviour, our ld.elf_so behaves sane too, so no
> changes there needed.
>
> Creating new "hidden" NEEDED entries would make it possible to catch
> wrong linker command lines, like what apparently the binutils folks
> tried to do with their changed default. However, this would be a
> (trivial) change in object format and require runtime linker changes.
>
> I would be happy if we could get the Solaris linker behaviour. The hidden
> needed extension might be something to evaluate closer and, if it shows real
> advantages, get discussed upstream.
>
> Unfortunately you can not get the "resolve symbol, but do not copy
> NEEDED" behaviour from gnu ld with any combination of options, and you
> could not get it from the old version of binutils either. This still
> leaves us with two IMHO broken behaviours as only short term options.
>
> I do not see any real harm done with reverting the default. What could
> possibly fail if third party software provides all -l args but we would
> copy NEEDED entries from indirect references?


I'm wondering which version of binutils was imported. I don't have
a NetBSD machine at hand right now, but on linux with he latest
development version:


$ cat main.c
#include <stdio.h>

extern char *libfunc(void);

int main(void)
{
        printf ("lib returns: '%s'\n", libfunc());
        return 0;
}
$ cat libmain.c

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

extern char *func_a(void);
extern char *func_b(void);

char *libfunc(void)
{
        size_t totlen;
        char *s1, *s2, *ret;

        s1 = func_a();
        s2 = func_b();

        totlen = strlen(s1) + strlen(s2) + 1;

        ret = malloc(totlen);
        if (! ret) {
                fprintf(stderr, "malloc failed: %s\n", strerror(errno));
                return "<error>";
        }

        strcpy (ret, s1);
        strcpy (ret + strlen(s1), s2);
        return ret;
}
$ cat libfunca.c

char *func_a(void)
{
        return "<funca>";
}
$ cat libfuncb.c

char *func_b(void)
{
        return "<funcb>";
}
$ cat mk
#!/bin/sh

gcc -fPIC -shared -o libfunca.so libfunca.c || exit 1
gcc -fPIC -shared -o libfuncb.so libfuncb.c || exit 1
gcc -fPIC -shared -o libmain.so libmain.c libfunca.so libfuncb.so || exit 1
#gcc -o main main.c libmain.so -Wl,-rpath-link,.
gcc -o main main.c libmain.so -Wl,-rpath,.
$ ./mk
$ ./main
lib returns: '<funca><funcb>'
$ readelf -a main | grep NEEDED
 0x0000000000000001 (NEEDED)             Shared library: [libmain.so]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
$ readelf -a libmain.so | grep NEEDED
 0x0000000000000001 (NEEDED)             Shared library: [libfunca.so]
 0x0000000000000001 (NEEDED)             Shared library: [libfuncb.so]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
$ ld --version
GNU ld (GNU Binutils) 2.24.51.20131014
Copyright 2013 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later 
version.
This program has absolutely no warranty.
$


Isn't that the desired behaviour?

regards,
chris