Re: [Qemu-devel] [PATCH] configure: eliminate Python dependency for --help

[Peter Maydell]

On 28 March 2017 at 14:08, Stefan Hajnoczi <address@hidden> wrote:
> The ./configure script should produce --help output even if Python is
> not installed.
>
> Listing trace backends is simple: show the names of all Python modules
> in scripts/tracetool/backend/ whose source code contains 'PUBLIC =
> True'.
>
> Perform the backend enumeration in shell instead of Python so that we
> can move the Python check until after ./configure --help.
>
> Reported-by: Peter Maydell <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>

Thanks. I think we should postpone this to 2.10 since we've had
this behaviour since forever, but it's a useful start to getting
our --help text into a less confusing place in configure.

> @@ -1328,7 +1313,7 @@ Advanced options (experts only):
>                             set block driver read-only whitelist
>                             (affects only QEMU, not qemu-img)
>    --enable-trace-backends=B Set trace backend
> -                           Available backends: $($python 
> $source_path/scripts/tracetool.py --list-backends)
> +                           Available backends: $(grep -le 
> '^PUBLIC\s*=\s*True$' scripts/tracetool/backend/*.py | sed -e 
> 's/^.*\/\(.*\)\.py$/\1/' | xargs echo)


'\s' doesn't work with NetBSD grep (it isn't POSIX). I think you need
   '^PUBLIC[[:space:]]*=[[:space:]]True'

(or just use ' ' since we don't have to contend with tabs here, as
you suggested on IRC).

I think we should also move the determining of the list of backends
out of the --help text itself, so set an avail_trace_backends
variable first and then just substitute the variable here.

thanks
-- PMM