Re: No need for object file removal before compilation

[Bob Friesenhahn]

On Thu, 10 Apr 2008, Ralf Wildenhues wrote:

> OK to apply?  I fail to see why it's necessary to remove these files.
> If they existed from a previous compile, they are outdated, so what.
> But I may be overlooking something here.

Removing the object file in advance accomplishes several things:

  o It ensures that the output object file is the result of the
    current compile.

  o It ensures that the output object file is owned by the person
    doing the build.

  o If the existing object file was a link, then it assures that an
    object file is written in place of the link rather than overwriting
    the file pointed to by the link.

The above assumes that the compiler may not be completely well behaved 
in that it might not unlink the output file in advance.

I am familiar with the link issue since years ago I implemented a 
build system for a project so large that the built product was larger 
than the individual developer's hard drives could support.  So there 
was a central weekly build that developers built link trees to, and 
then any updated objects were written to the developer's drives.  It 
worked amazingly well.

I think that removing the object file in advance is a wise idea so 
this patch should not be applied even if it makes libtool slower.

Bob

> Thanks,
> Ralf
>
> 2008-04-10  Ralf Wildenhues  <address@hidden>
>
>         * libltdl/config/ltmain.m4sh (func_mode_compile): No need to
>         remove old output files before compilation.
>
> Index: libltdl/config/ltmain.m4sh
> ===================================================================
> RCS file: /cvsroot/libtool/libtool/libltdl/config/ltmain.m4sh,v
> retrieving revision 1.102
> diff -u -r1.102 ltmain.m4sh
> --- libltdl/config/ltmain.m4sh  16 Mar 2008 08:34:25 -0000      1.102
> +++ libltdl/config/ltmain.m4sh  9 Apr 2008 23:33:43 -0000
> @@ -1437,7 +1423,6 @@
>       removelist="$lobj $libobj ${libobj}T"
>     fi
>
> -    $opt_dry_run || $RM $removelist
>     trap "$opt_dry_run || $RM $removelist; exit $EXIT_FAILURE" 1 2 15
>
>     # On Cygwin there's no "real" PIC flag so we must build both object types
> @@ -1568,7 +1553,6 @@
>
>       # Suppress compiler output if we already did a PIC compilation.
>       command="$command$suppress_output"
> -      $opt_dry_run || $RM "$obj" "$output_obj"
>       func_show_eval_locale "$command" \
>         '$opt_dry_run || $RM $removelist; exit $EXIT_FAILURE'

======================================
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/