Re: [PATCH v2 10/10] detect-compiler: detect clang even if it found CUDA

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Mar 26, 2025, 18:07 UTC
Message-ID: <CAPig+cR+ESNg4tV1G6jbKKeRKABD053qZcG0BoFuQ7aC+1tGYw@mail.gmail.com>
In-Reply-To: <20250326174127.GA2508080@coredump.intra.peff.net>

On Wed, Mar 26, 2025 at 1:44 PM Jeff King <peff@peff.net> wrote:

Show 12 quoted lines

> On Tue, Mar 25, 2025 at 11:32:14PM +0000, Johannes Schindelin via GitGitGadget wrote:
> > Let's unconfuse the script by letting it parse the first matching line
> > and ignore the rest.
>
> Makes sense. I wondered if this:
>
> >  get_version_line() {
> > -     LANG=C LC_ALL=C $CC -v 2>&1 | grep ' version '
> > +     LANG=C LC_ALL=C $CC -v 2>&1 | sed -n '/ version /{p;q}'
>
> might be more readable with "grep -m1", but it looks like "-m" is not in
> POSIX. So what you wrote is probably safer.

It's probably an indication that I've done too much `sed` programming, but I find Dscho's version more obvious. That aside, your response made me take a closer look at what Dscho wrote and I noticed that it is syntactically flawed, at least for BSD-lineage `sed`. Testing on macOS reveals that this is indeed so:

    % LANG=C LC_ALL=C cc -v 2>&1 | sed -n '/ version /{p;q}'
    sed: 1: "/ version /{p;q}": extra characters at the end of q command

The problem is that the `q` function takes no arguments, but BSD-lineage `sed` thinks that the closing `}` is an argument rather than a terminator. Fixing this requires inserting a terminator after `q`, which will be either a newline character or a semicolon. So, the correct form is:

    sed -n '/ version /{p;q;}