Re: multi-threaded compiling

[Mischa Baars]

On Mon, Mar 11, 2024 at 10:26 PM Chet Ramey <chet.ramey@case.edu> wrote:

> On 3/11/24 3:44 PM, Mischa Baars wrote:
> > On Mon, 11 Mar 2024, 20:20 Chet Ramey, <chet.ramey@case.edu
> > <mailto:chet.ramey@case.edu>> wrote:
> >
> >     On 3/11/24 2:50 PM, Mischa Baars wrote:
> >      > Which sort of brings us back to the original question I suppose.
> Who
> >     does
> >      > that line of code function from a script and why does it fail
> from the
> >      > command line?
> >
> >     Job control and when the shell notifies the user about job
> completion,
> >     most likely, two of the relevant things that differ between
> interactive
> >     and non-interactive shells.
> >
> >
> > Wasn't expecting any better answer, but thanks anyway.
>
> OK, here's the longer answer. When the shell is interactive, and job
> control is enabled, the shell prints job completion notifications to
> stdout at command boundaries. Once the shell notifies the user of a
> job's completion, it is no longer `new' (or the `next', whichever
> mnemonic you prefer), and `wait -n' will not return it.
>
> So if you include the complete output of an interactive shell executing
> the above list (with the obvious corrections already discussed), you'll
> get a series of
>
> 32 messages about job creation
> 32 notifications of job exits, with exit status (they exit immediately,
> after all)
> 32 error messages because the user has already been notified of the
> job's completion and the shell has reaped it (so it is no longer the
> `next' job to exit)
>
> When the shell is not interactive, it only prints job notifications to
> stdout when the job is terminated by a signal, so the jobs are available
> to `wait -n'.
>
> There was quite a long discussion about this aspect of `wait -n' behavior
> a couple of months ago, starting at
>
> https://lists.gnu.org/archive/html/bug-bash/2024-01/msg00104.html
>
>
> > And the script from directory 'two'? How do I pass this string through
> the
> > CFLAGS variable to the compiler? What am I doing wrong in #3 of the
> script?
>
> You're not taking word splitting into account. It seems like you want
> selective word splitting -- for the embedded double quotes in the various
> elements of CFLAGS to have some semantic meaning and somehow inhibit
> word splitting. Quotes are special to the parser, not when they are in
> the results of word expansion. If you want the parser to evaluate the
> results of word expansion, you're going to have to run it through the
> parser again, using something like `eval'.
>
> It's clearer if you replace `gcc' in your command with
>
> printf '<%s> '
>
> and `./main' with `echo'.
>
> Yes. Now I see a difference in all the different lines. I wasn't familiar
with this printf construct, but the results are clear:

Using make:

<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>

Using ./make.sh:

<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__=one and two>

and either for unquoted variable in #3

<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__="one><and><two">
<gcc><-o><main><main.c><-D__STRINGIZED__=0><-D__STRING__="one><and><two">
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__="one><and><two">
<gcc><-o><main><main.c><-D__STRINGIZED__=1><-D__STRING__="one><and><two">

or for double quoted variable in #3

<gcc><-o><main><main.c><-D__STRINGIZED__=0 -D__STRING__="one and two">
<gcc><-o><main><main.c><-D__STRINGIZED__=0 -D__STRING__="one and two">
<gcc><-o><main><main.c><-D__STRINGIZED__=1 -D__STRING__="one and two">
<gcc><-o><main><main.c><-D__STRINGIZED__=1 -D__STRING__="one and two">

So... how do I fix it?


> --
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
>                  ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/
>
>