[PATCH] check-non-portable-shell: support Perl versions older than 5.10

For thoroughness when checking for one-shot environment variable assignments at shell function call sites, check-non-portable-shell stitches together incomplete lines (those ending with backslash). This allows it to correctly flag such undesirable usage even when the variable assignment and function call are split across lines, for example:

    FOO=bar \
    func

where 'func' is a shell function.

The stitching is accomplished like this:

    while (<>) {
        chomp;
        # stitch together incomplete lines (those ending with "\")
        while (s/\\$//) {
            $_ .= readline;
            chomp;
        }
        # detect unportable/undesirable shell constructs
        ...
    }

Although this implementation is well supported in reasonably modern Perl versions (5.10 and later), it fails in a couple ways with older versions (such as Perl 5.8 shipped with ancient Mac OS 10.5).

In particular, in older Perl versions, 'readline' is not connected to the file handle associated with the "magic" while (<>) {...} construct, so 'readline' throws a "readline() on unopened filehandle" error. Furthermore, $_ assigned by the outer while-loop is read-only, so the attempt to modify it via "$_ .= readline" in the inner while-loop fails with a "Modification of a read-only value" error.

Avoid both problems by collecting the stitched-together line in a variable other than $_ and dropping the inner loop entirely.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
---
 t/check-non-portable-shell.pl | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)