On Tue, Aug 19, 2025 at 12:56:48PM +0100, Peter Maydell wrote:
> Newer versions of Perl (5.41.x and up) emit a warning for code in
> kernel-doc:
> Possible precedence problem between ! and pattern match (m//) at
> /scripts/kernel-doc line 1597.
>
> This is because the code does:
> if (!$param =~ /\w\.\.\.$/) {
>
> In Perl, the ! operator has higher precedence than the =~
> pattern-match binding, so the effect of this condition is to first
> logically-negate the string $param into a true-or-false value and
> then try to pattern match it against the regex, which in this case
> will always fail. This is almost certainly not what the author
> intended.
>
> In the new Python version of kernel-doc in the Linux kernel,
> the equivalent code is written:
>
> if KernRe(r'\w\.\.\.$').search(param):
> # For named variable parameters of the form `x...`,
> # remove the dots
> param = param[:-3]
> else:
> # Handles unnamed variable parameters
> param = "..."
>
> which is a more sensible way of writing the behaviour you would
> get if you put in brackets to make the regex match first and
> then negate the result.
>
> Take this as the intended behaviour, and update the Perl to match.
>
> For QEMU, this produces no change in output, presumably because we
> never used the "unnamed variable parameters" syntax.
>
> Cc: [email protected]
> Signed-off-by: Peter Maydell <[email protected]>
> ---
> This obviously will clash with the "import the python script"
> patchseries, but I figured it was worth providing the minimal
> fix for the benefit of stable backports.
>
> The kernel's copy of kernel-doc.pl still has this bug.
> ---
> scripts/kernel-doc | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/kernel-doc b/scripts/kernel-doc
> index fec83f53eda..117ec8fcd1f 100755
> --- a/scripts/kernel-doc
> +++ b/scripts/kernel-doc
> @@ -1594,13 +1594,12 @@ sub push_parameter($$$$$) {
>
> if ($type eq "" && $param =~ /\.\.\.$/)
> {
> - if (!$param =~ /\w\.\.\.$/) {
I think it would be possible to change this only line to
collapse the ! and =~ into the !~ operator:
if ($param !~ /\w\.\.\.$/) {
> - # handles unnamed variable parameters
> - $param = "...";
> - }
> - elsif ($param =~ /\w\.\.\.$/) {
> + if ($param =~ /\w\.\.\.$/) {
> # for named variable parameters of the form `x...`, remove the
> dots
> $param =~ s/\.\.\.$//;
> + } else {
> + # handles unnamed variable parameters
> + $param = "...";
> }
> if (!defined $parameterdescs{$param} || $parameterdescs{$param} eq
> "") {
> $parameterdescs{$param} = "variable arguments";
> --
> 2.43.0
>
>
With regards,
Daniel
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