gcc and /usr/lib/*.ld files

[William Roberts]

A further problem has surfaced with the latest gcc from John
Coolidge (gcc-1.37.94), when used with those funny
/usr/lib/*.ld files to achieve extra control over the layout of
the COFF binary produced by the final ld.

Imagine a file foo.c containing the usual "hello world"
program, and compile it to get foo.o. We used to be able to say

gcc -N foo.o /usr/lib/unshared.ld

and get a working binary: using the previous version of gcc
that produced junk binaries if you tried to use shared
libraries.

Now we get the following effect:

% gcc -v -N foo.o /usr/lib/unshared.ld
gcc version 1.37.94
 ld -L/usr/local/lib -L/usr/local/Gnu/lib -N
/lib/crt1.o /lib/crt2.o foo.o /usr/lib/unshared.ld
/usr/lib/gcc-gnulib /usr/lib/gcc-gnulib -lc /lib/crtn.o
/usr/lib/gcc-gnulib /usr/lib/shlib.ld
ld warning: Sections .text .data or .bss not found.
Optional header may be useless
% size a.out


Size of a.out:  0x23fc

        Section         Size      Physical Address    Virtual Address
        .text        0x00001d00      0x00000000         0x00000000
        .data        0x0000058c      0x00001d00         0x00001d00
        .bss         0x00000170      0x0000228c         0x0000228c
        .text        0x00000000      0x000023fc         0x000023fc
        .data        0x00000000      0x00400000         0x00400000
        .bss         0x00000000      0x00400000         0x00400000
% a.out
Segmentation fault (core dumped)
%

There are two separate problems:

1) The presence on an explicit *.ld file does not prevent gcc from
   putting /usr/lib/shlib.ld on the end. Using the real A/UX cc instead
   produces

% /bin/cc -v -N foo.o /usr/lib/unshared.ld
/bin/ld /lib/crt1.o /lib/crt2.o -N foo.o /usr/lib/unshared.ld -lc
%

2) The unshared.ld should be linked with /lib/crt0.o instead of
   /lib/crt1.o and /lib/crt2.0 - A/UX cc gets this wrong as well!

I don't know what the correct answer should be: /usr/lib/unshared.ld itself
looks out of date (mentions obselete magic numbers, for instance).
What is correct System V semantics for all this?


The work-around is to do the ld explicitly if you need the
extra functionality that the *.ld files provide.




-- 

William Roberts                 ARPA: liam at cs.qmw.ac.uk
Queen Mary & Westfield College  UUCP: liam at qmw-cs.UUCP
Mile End Road                   AppleLink: UK0087
LONDON, E1 4NS, UK              Tel:  071-975 5250 (Fax: 081-980 6533)