environment variables in ld scripts

[Jay Braun]

I have inherited an application that makes extensive use of ld scripts. The former developer hard-coded many absolute directory paths into these scripts, e.g.:

-L /home/harold/libs -( -lnwiss -lr -)
@/home/harold/libs lib.ld

I would like to use environment variables so that I can use, say /home/jay/ rather than /home/harold. So I'll define:

export APP_LIBS=/home/jay/libs

but neither of the following works:

-L $APP_LIBS -( -lnwiss -lr -)
@$APP_LIBS lib.ld

Is there a special notation for employing environment variables in ld scripts?

Thanks,
Jay

[Tauno Voipio]

This seems more as the shell script to start ld (or maybe even gcc),
than the ld script.

Please check.

--

Tauno Voipio

[John Reiser]

> I have inherited an application that makes extensive use of ld scripts. ...

> -L $APP_LIBS -( -lnwiss -lr -)

The shell expands environment variable APP_LIBS here as part of a ld (or gcc) command line.

> @$APP_LIBS lib.ld
Inside a linker script, then ld does not expand shell environment variables.

> Is there a special notation for employing environment variables in ld scripts?

No; instead you must perform the expansion before invoking ld.
One way to do this is with a shell "Here Document" which is invoked by the syntax "<<".
See the documentation for any shell, such as "man bash" or "info bash".
Example:

cat - > my_linker_script.txt <<EOF
@$APP_LIBS lib.ld
EOF

The shell will expand "$APP_LIBS" as it reads the lines until EOF.
The utility program 'cat' then writes those lines to its stdout,
which in this case is re-directed to file "my_linker_script.txt".

ld ... -T my_linker_script.txt ...

Use the file my_linker_script.txt with the already-expanded environment variables.

--

[Jay Braun]

[Jay Braun]

We decided to build a bash script that generates the ld script with a multi-line echo. Environment variables are part of the script, and are written to the temporary ld file as full path names. The bash script them does a "chmod +x" on the ld file, and executes it. The ld file can then be deleted because the bash script has the permanent contents.

Thanks very much,
Jay

On Tuesday, April 23, 2013 8:34:29 AM UTC-7, John Reiser wrote:
> > I have inherited an application that makes extensive use of ld scripts. ...
>
>
>
> > -L $APP_LIBS -( -lnwiss -lr -)
>
> The shell expands environment variable APP_LIBS here as part of a ld (or gcc) command line.
>
>
>
> > @$APP_LIBS lib.ld
>
> Inside a linker script, then ld does not expand shell environment variables.
>
>
>
> > Is there a special notation for employing environment variables in ld scripts?
>
> No; instead you must perform the expansion before invoking ld.
>
> One way to do this is with a shell "Here Document" which is invoked by the syntax "<<".
>
> See the documentation for any shell, such as "man bash" or "info bash".
>
> Example:
>
>
>
> cat - > my_linker_script.txt <