On Mon, Sep 18, 2023 at 12:35:53PM -0400, Taylor Blau wrote:

When validating email addresses with `extract_valid_address_or_die()`,
we print out a helpful error message when the given input does not
contain a valid email address.

However, the pre-image of this patch looks something like:

    my $address = shift;
    $address = extract_valid_address($address):
    die sprintf(__("..."), $address) if !$address;

which fails when given a bogus email address by trying to use $address
(which is undef) in a sprintf() expansion, like so:

    $ git.compile send-email --to="pi <pi@pi>" /tmp/x/*.patch --force
    Use of uninitialized value $address in sprintf at /home/ttaylorr/src/git/git-send-email line 1175.
    error: unable to extract a valid address from:

Yeah, we overwrite the variable we're reporting on, so I don't think the
original could possibly work. Your fix makes sense.

This regression dates back to e431225569 (git-send-email: remove invalid
addresses earlier, 2012-11-22), but became more noticeable in a8022c5f7b
(send-email: expose header information to git-send-email's
sendemail-validate hook, 2023-04-19), which validates SMTP headers in
the sendemail-validate hook.

I didn't quite understand how a8022c5f7b made this worse, but I guess we
just call it the bad function in more instances. The bug is definitely
from e431225569, though.

-Peff