Re: [Xen-devel] [PATCH 16/16] configure: do_compiler: Dump some extra info under bash

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Anthony PERARD writes ("Re: [PATCH 16/16] configure: do_compiler: Dump some 
extra info under bash"):
> On Thu, Apr 19, 2018 at 05:45:19PM +0100, Ian Jackson wrote:
> > +funcs: ${FUNCNAME}
> > +lines: ${BASH_LINENO}
> > +files: ${BASH_SOURCE}"
> >      echo $compiler "$@" >> config.log
> >      $compiler "$@" >> config.log 2>&1 || return $?
> >      # Test passed. If this is an --enable-werror build, rerun
> 
> How is this usefull? All I have in my config.log is a lot of:
>   funcs: do_compiler
>   lines: 91
>   files: ./configure
> 
> And one:
>   funcs: do_compiler
>   lines: 95
>   files: ./configure
> 
> It still don't tell me which test had runned.

You are right.  Perhaps my testing was inadequate.  I wrote this a
long while ago, and if there was a syntax along these lines that DTRT
in both bash and dash in my tests it is long gone.  Starting de novo,
the following code works for me:

    (echo >>config.log "
 funcs: ${FUNCNAME[*]}
 lines: ${BASH_LINENO[*]}
 files: ${BASH_SOURCE[*]}") 2>/dev/null ||:

With bash I get the expected information in config.log, which looks
like this:

 funcs: do_compiler do_cc compile_prog cc_has_warning_flag main
 lines: 91 124 1720 1724 0
 files: ./configure ./configure ./configure ./configure ./configure

With dash the script runs but there is nothing from this segment in
the log.  Without the 2>/dev/null, it prints
  ./configure: 63: ./configure: Bad substitution
so the syntax error is indeed being suprresed and ignored.

The ( ) is necessary because syntax errors are not like set -e errors:
they cause the shell process to exit.

I will update the patch and put some of this info in the commit
message.

Ian.

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