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    SubjectRe: [PATCH] Speed up "make headers_*"
    On Sun, Jun 8, 2008 at 11:47 AM, Sam Ravnborg <sam@ravnborg.org> wrote:
    > This is just a heads up patch if anyone is interested.
    > I finally took the time needed to optimize the
    > make headers_* targets.
    >
    > On my box it now takes less than 10 seconds to run
    > the full install + check cycle.
    > And it generates roughtly one screen full of output.
    >
    > Compare that to ~31 seconds and output filling up
    > my scroll back buffer.

    Nice :-)

    > Comments (especially to the perl scripts) are welcome.

    Will do! Some of my comments are a bit on the pedantic side, so you
    choose yourself which ones you want to heed!

    > diff --git a/scripts/headers_check.pl b/scripts/headers_check.pl
    > new file mode 100644
    > index 0000000..dfb2ec7
    > --- /dev/null
    > +++ b/scripts/headers_check.pl
    > @@ -0,0 +1,48 @@
    > +#!/usr/bin/perl
    > +#
    > +# headers_check.pl execute a number of trivial consistency checks
    > +#
    > +# Usage: headers_check.pl dir [files...]
    > +# dir..: dir to look for included files
    > +# files: list of files to check
    > +#
    > +# The script reads the supplied files line by line and:
    > +#
    > +# 1) for each include statement it checks if the
    > +# included file actually exists.
    > +# Only include files located in asm* and linux* are checked.
    > +# The rest are assumed to be system include files.
    > +#
    > +# 2) TODO

    'use strict' and 'use warnings' is recommended. You have "my" on the
    variables anyway (which is a good thing!).

    > +
    > +my ($dir, @files) = @ARGV;
    > +
    > +my $ret = 0;
    > +my $lineno = 0;
    > +my $filename;
    > +
    > +foreach $file (@files) {
    > + $filename = $file;
    > + open(FILE, "< $filename") or die "$filename: $!\n";

    I personally prefer to put '<', $filename here instead of mashing them
    together as one string. I don't know if it really matters.

    If you want to compile with strict/warnings here, you should replace
    FILE with "my $fh" here

    > + $lineno = 0;
    > + while ($line = <FILE>) {

    ...and use <$fh> here.

    > + $lineno++;
    > + &check_include();

    The & should be gone (see perldoc -q 'calling a function')

    > + }
    > + close(FILE);
    > +}
    > +exit($ret);

    The parentheses are not needed for most of the built-in functions.

    > +
    > +my $includere = qr/^\s*#\s*include\s+<(.*)>/;

    What seems to be the purpose of this, also what's up with the funny name? :-D

    > +sub check_include()

    The parentheses should be gone. This has something to do with
    prototypes and should normally not be used.

    > +{
    > + if ($line =~ m/^\s*#\s*include\s+<(.*)>/) {
    > + my $inc = $1;

    This could also be written as if (my($inc) = $line =~ ...), and you
    bypass the use of $1, which is often error-prone... but it's correct
    in this case and is simply a matter of taste.

    > + if ($inc =~ m/^asm/ || $inc =~ m/^linux/) {
    > + if (!(stat($dir . "/" . $inc))) {

    May use unless() instead of if(!()) here. But that's just perl pedantry.

    > + printf STDERR "$filename:$lineno: included file '$inc' is not exported\n";
    > + $ret = 1;
    > + }
    > + }
    > + }
    > +}

    More or less the same comments would apply to the next script as well.

    > diff --git a/scripts/headers_install.pl b/scripts/headers_install.pl
    > new file mode 100644
    > index 0000000..8aa66af
    > --- /dev/null
    > +++ b/scripts/headers_install.pl
    ...
    > + $line =~ s/([\s(])__user\s/\1/g;
    ...

    Use of $1 instead of \1 is recommended, see perldoc perlre ("Warning
    on \1 vs $1").


    Vegard

    --
    "The animistic metaphor of the bug that maliciously sneaked in while
    the programmer was not looking is intellectually dishonest as it
    disguises that the error is the programmer's own creation."
    -- E. W. Dijkstra, EWD1036


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