Update with NEWS from 1.4.23-1.4.25

[xapian.git] / xapian-maintainer-tools / xapian-check-patch

#! /usr/bin/perl -w
# Copyright (c) 2007-2024 Olly Betts
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to
# deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
# sell copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.

require 5.000;
use strict;
use POSIX;

if (defined $ARGV[0] && $ARGV[0] eq '--help') {
    print <<END;
Syntax: $0 [PATCH]...

Nit-pick Xapian patches.

A patch can be supplied on stdin, or one or more patch files listed on the
command line.

Produces output suitable for use with vim's quick-fix mode, and similar
features in other editors.

Example usage:

git diff master.. | xapian-check-patch > tmp.qf
vim -q tmp.qf
END
    exit 0;
}

my ($fnm, $lineno);
my ($last_fullline, $fullline);
my $ext;
my %count;

sub diagnostic_ {
    my ($type, $msg, $n, $l) = @_;
    print "$fnm:$n: $type: $msg";
    if (defined $l) {
        print ": $l";
    } else {
        print "\n";
    }
    ++$count{$type};
}

# Report a diagnostic in the current line.
sub diagnostic {
    my ($type, $msg) = @_;
    diagnostic_($type, $msg, $lineno, $fullline);
}

# Report a diagnostic in the previous line.
sub diagnostic_last {
    my ($type, $msg) = @_;
    diagnostic_($type, $msg, $lineno - 1, $last_fullline);
}

sub count_columns {
    my $s = shift;
    my $len = 0;
    for my $i (0 .. length($s) - 1) {
        if (substr($s, $i, 1) eq "\t") {
            # Advance to next multiple of 8 column.
            $len = $len + (8 - $len % 8);
        } else {
            ++$len;
        }
    }
    return $len;
}

sub check_comment_content {
    local $_ = shift;
    if (/\\([abcefp]|brief|code|deprecated|endcode|exception|file|internal|li|param|private|return|todo)\b/) {
        diagnostic('error', "Doxygen command '\\$1' introduced by '\\' not '\@'");
    }
    if (/\@\s+([abcefp]|brief|code|deprecated|endcode|exception|file|internal|li|param|private|return|todo)\b/) {
        diagnostic('error', "Broken Doxygen command: whitespace between '\@' and '$1'");
    }
    if (/(\@[a-z]+)\s+\1\b/) {
        diagnostic('error', "Double Doxygen command: '$1 $1'");
    }
}

my $add_lines = 0;
my $del_lines = 0;
my $files = 0;
# SVN property changes don't have an "Index: [...]" line.
my $want_tabs = -1;
my $check_indent = 0;
my $check_trailing = 0;
my $check_space_tab = 0;
my $check_end_new_line = 0;
my $in_comment = 0;
my $lang;
my $header_guard_macro;
my $last_first_char = '';
my $in_ternary;
my $preproc;
my $preproc_continuation;
my ($top_level, $next_top_level); # undef for unknown, 0 for no, 1 for yes.
my $last_line_blank = 0;
my $last_line_block_start;
my $last_line_block_end;
my $penultimate_line_block_start;
# Indent in columns expected for this line (undef if we don't know).
my $indent;
# True if the indent increased due to a "case" or "default" without a { - this
# means that a following "case"/"default" should not be indented.
my $case_no_brace;
# Current file is a C/C++ header file.
my $header;
# First line number for doxygen @file comment check.
my $doxygen_first_line;
while (<>) {
    if (defined $next_top_level) {
        $top_level = $next_top_level;
        $next_top_level = undef;
    }

    if (/^Index: (.+)/ || m!^diff --git a/.+ b/(.+)! || m!^\+\+\+ (\S+)!) {
        ++$files;
        $fnm = $1;
        (($ext) = ($fnm =~ /\.([\w.]+)$/)) or $ext = '';
        $lineno = 1;
        $lang = undef;
        $in_comment = 0;
        $header_guard_macro = undef;
        $in_ternary = 0;
        $preproc = 0;
        $preproc_continuation = 0;
        $top_level = undef;
        $header = 0;
        # Don't know!
        $want_tabs = -1;
        $check_indent = 0;
        $check_space_tab = 1;
        $check_trailing = 1;
        $doxygen_first_line = 1;
        $check_end_new_line = 1;
        if ($fnm =~ m!xapian-applications/omega/testfiles!) {
            $check_space_tab = 0;
            $check_trailing = 0;
            $doxygen_first_line = 0;
            $check_end_new_line = 0;
        } elsif ($ext eq 'cc') {
            if ($fnm =~ m!\b(?:cdb|portability/mkdtemp)! ||
                $fnm =~ m!\bcommon/getopt\.cc$! ||
                $fnm =~ m!\bomega/md5\.cc$! ||
                $fnm =~ m!\bcommon/msvc_dirent\.cc$!) {
                $check_trailing = 0;
            } else {
                $lang = 'c++';
                $want_tabs = 1 unless ($fnm =~ m!\blanguages/steminternal\.cc$!);
                $check_indent = 1;
            }
        } elsif ($ext eq 'c') {
            if ($fnm =~ m!\blanguages/compiler/! ||
                $fnm =~ m!/lemon\.c$!) {
                $check_trailing = 0;
            } else {
                $lang = 'c';
                $want_tabs = 1;
                $check_indent = 1;
            }
        } elsif ($ext eq 'h') {
            if ($fnm =~ m!\binclude/xapian/intrusive_ptr\.h! ||
                $fnm =~ m!\blanguages/compiler/! ||
                $fnm =~ m!\bcommon/msvc_dirent\.h$! ||
                $fnm =~ m!\bcommon/heap\.h$! ||
                $fnm =~ m!/omega/cdb! ||
                $fnm =~ m!\bportability/mkdtemp!) {
                $check_trailing = 0;
            } else {
                $header = 1;
                $lang = 'c++';
                $want_tabs = 1;
                $check_indent = 1;
            }
        } elsif ($ext eq 'lemony') {
            $lang = 'c++';
            $want_tabs = 1;
        } elsif ($ext eq 'lt') {
            $want_tabs = 0;
            $check_trailing = 0;
        } elsif ($ext eq 'py' || $ext eq 'py.in') {
            $lang = 'py';
            $want_tabs = 0;
        } elsif ($ext eq 'rb') {
            $lang = 'rb';
            $want_tabs = 0;
        } elsif ($ext eq 'sbl') {
            $check_space_tab = 0;
            $check_trailing = 0;
        } elsif ($ext eq 'patch') {
            $check_space_tab = 0;
        } elsif ($ext eq 'txt') {
            # Imported text file with trailing whitespace.
            if ($fnm =~ m!/testdata/etext\.txt$!) {
                $check_trailing = 0;
            }
        } elsif ($fnm =~ m!(?:^|/)Makefile!) {
            $lang = 'make';
            $want_tabs = 1;
        } elsif ($fnm =~ m!(?:^|/)ChangeLog\b!) {
            $lang = 'changelog';
            $want_tabs = 1;
        }
        # print STDERR "$fnm: lang=" . ($lang // "UNKNOWN") . "\;
        next;
    }
    my $pre3 = substr($_, 0, 3);
    if ($pre3 eq '@@ ') {
        /^\@\@ -\d+,\d+ \+(\d+),\d+\b/ and $lineno = $1;
        $next_top_level = ($lineno == 1) ? 1 : undef;
        $in_comment = ($lineno == 1) ? 0 : undef;
        $last_line_blank = 0;
        $last_line_block_start = undef;
        $last_line_block_end = undef;
        $penultimate_line_block_start = undef;
        $indent = undef;
        $last_first_char = '';
        $last_fullline = undef;
        next;
    }
    if ($pre3 eq '---' || $pre3 eq '+++') {
        next;
    }

    if (!/^.\s*$/) {
        $next_top_level = (/^.\s/ ? 0 : 1);
    }

    my $line_blank = /^[+ ]\s*$/;

    $fullline = $_;
    my $first_char = substr($fullline, 0, 1);

    if (defined $lang && ($lang eq 'c++' || $lang eq 'c')) {
        if (!defined $in_comment) {
            # Decide if we're in a C-style comment for the first line of a hunk.
            $in_comment = /^.\s*\*+\s/;
        }
        if ($lineno == $doxygen_first_line && m!^\+!) {
            if ($doxygen_first_line == 1 && m,^\+%include\b\s*\{,) {
                # If the first line is %include{... check the second.
                $doxygen_first_line = 2;
            } elsif (m!^\+/\*\*\s+\@file\s*(.*)!) {
                if (length($1)) {
                    diagnostic('error', "Doxygen \@file should not list explicit filename");
                }
            } elsif ($fnm =~ m!\bomega/md5\.h$!) {
                # Imported file.
            } else {
                diagnostic('error', "Doxygen \@file missing");
            }
        }

        # Uncomment commented out parameter names: foo(int /*bar*/) -> foo(int bar)
        s!/\*([A-Za-z_][A-Za-z_0-9]*)\*/([,)])!$1$2!g;

        # Check for comments without a space before the comment text.
        if (m!^\+.*\s/([*/]{1,2})[A-Za-z0-9]!) {
            if ($ext eq 'lemony' && $1 eq '*' && $' =~ m!^\w*-overwrites-\w+\*/!) {
                # Magic comment in lemon grammar - lemon requires no spaces.
            } else {
                diagnostic('error', "Missing space between comment characters and comment text");
            }
        }

        # Trim comments:
        if (!$in_comment) {
            if (s! /\*(.*?)\*/ ! !g) {
                # C-style comment with spaces around, e.g.
                # { T = P->as_phrase_query(); /*T-overwrites-P*/ }
                if ($first_char eq '+') {
                    check_comment_content($1);
                }
                s/\s+$//;
            }
            if (s!/\*(.*?)\*/!!g) {
                # C-style comment without spaces on both sides, e.g.:
                #    foo(); /* blah blah */
                if ($first_char eq '+') {
                    check_comment_content($1);
                }
                s/\s+$//;
            }
            if (s!//(.*)!!) {
                # Single line comment, e.g.:
                #    // blah blah
                if ($first_char eq '+') {
                    check_comment_content($1);
                }
                s/\s+$//;
            }
            # Take care to avoid interpreting "foo/*" as a comment start.
            if (s!^.(?:[^"]+?|"(?:[^\\"]*?|\\.)*?")*?/\*(.*)!!g) {
                if ($first_char eq '+') {
                    check_comment_content($1);
                }
                s/\s+$//;
                $in_comment = 1;
            }
        } else {
            if (s!^.\s*\*+(.*)\*/!$first_char!) {
                # End of multiline comment with leading *, e.g.:
                #    *  blah blah */
                if ($first_char eq '+') {
                    check_comment_content($1);
                }
                s/\s+$//;
                $in_comment = 0;
            } elsif (s!^.(.*)\*/!$first_char!) {
                # End of multiline comment without leading *, e.g.:
                #     blah blah */
                if ($first_char eq '+') {
                    check_comment_content($1);
                }
                $in_comment = 0;
            } else {
                if ($first_char eq '+') {
                    if (m!^.\s*\*+(.*)!) {
                        # In multiline comment with leading *.
                        check_comment_content($1);
                    } else {
                        # In multiline comment without leading *.
                        check_comment_content(substr($_, 1));
                    }
                }
                $_ = $first_char;
            }
        }
    } elsif (defined $lang && $lang eq 'py') {
        # Trim comments:
        if (s!#.*!!g) {
            s/\s+$//;
        }
    } elsif (defined $lang && $lang eq 'rb') {
        # Trim comments:
        if (s!#.*!!g) {
            s/\s+$//;
        }
    }

    # Default to not being in a comment for languages other than C/C++.
    $in_comment //= 0;

    # Replace multiple spaces before line continuation marker:
    s!  +\\$! \\!;

    if (defined $lang && ($lang eq 'c++' || $lang eq 'c')) {
        if ($first_char eq '+') {
            my $expandedline = '';
            for my $i (1..length($fullline) - 1) {
                my $ch = substr($fullline, $i, 1);
                if ($ch eq "\t") {
                    $expandedline .= ('.' x (8 - length($expandedline) % 8));
                } else {
                    $expandedline .= $ch;
                }
            }
            chomp($expandedline);
            if (length($expandedline) > 80 &&
                # Logging annotations aren't really for human eyes.
                !/^\+[ \t]*LOGCALL/ &&
                # Allow length up to 84 if " in first column for formatting
                # text blocks (the extra 4 being "\n").
                (length($expandedline) > 84 || !/^\+"/) &&
                # Allow longer copyright lines.
                $fullline !~ m,^\+[ /]\* Copyright , &&
                # Allow long initialisers (e.g. for testcases).
                ! /^\+\s*\{.*\},?$/ &&
                # Don't force wrapping of a long #error message.
                !/^\+#\d*(error|warning)\b/) {
                diagnostic('error', "Line extends beyond column 80 (to column ".length($expandedline).")");
            }
        }
        if (m,^\+\s+LOGCALL(?:_[A-Z0-9]+)*\([^"]*"[^"]*(?<!operator)\(,) {
            diagnostic('error', "Don't include parentheses in debug logging method/class name");
        }
        if (/^\+\s+LOGCALL(?:_[A-Z0-9]+)*\(.*,$/) {
            diagnostic('error', "Don't wrap long LOGCALL lines");
        }
        if (/^\+\s+(LOGCALL(?:_STATIC)?)\([^,]*,\s*void,$/) {
            diagnostic('error', "Use $1_VOID for a method with a void return type");
        }
        # Replace string literals containing escaped quotes:
        if (/['"]/) {
            my $quote = substr($_, $-[0], 1);
            my $start = $+[0];
            my $i = $start;
            my $esc = 0;
QUOTELOOP:  while (1) {
                if ($i >= length($_)) {
                    $_ = substr($_, 0, $start) . "X\n";
                    last;
                }
                my $c = substr($_, $i, 1);
                if ($c eq $quote) {
                    $_ = substr($_, 0, $start) . "X" . substr($_, $i);
                    $i = $start + 2;
                    # See if there's another string after this one:
                    while ($i != length($_)) {
                        $c = substr($_, $i, 1);
                        ++$i;
                        if ($c eq '"' || $c eq "'") {
                            $quote = $c;
                            $start = $i;
                            $esc = 0;
                            next QUOTELOOP;
                        }
                    }
                    last;
                }
                if ($c eq '\\') {
                    ++$i;
                    $c = substr($_, $i, 1);
                    if ($c eq 'x') {
                        ++$i while (substr($_, $i, 1) =~ /^[A-Fa-f0-9]$/);
                        next;
                    } elsif ($c =~ /^[0-7]/) {
                        my $j = $i;
                        ++$i while ($i - $j <= 3 && substr($_, $i, 1) =~ /^[0-7]$/);
                        next;
                    } elsif ($c eq '"' || $c eq "'") {
                        ++$esc;
                    }
                }
                ++$i;
            }
        }
    }

    if ($check_trailing && $fullline =~ /^\+.*[ \t]$/) {
        diagnostic('error', "added/changed line has trailing whitespace");
    }
    if ($check_space_tab && /^\+.* \t/) {
        diagnostic('error', "added/changed line has space before tab");
    }
    if ($want_tabs == 1 and /^\+\t* {8}/) {
        diagnostic('error', "added/changed line uses spaces for indentation rather than tab");
    }
    if (!$want_tabs and /^\+ *\t/) {
        diagnostic('error', "added/changed line uses tab for indentation rather than spaces");
    }
    if ((!defined $lang || $lang ne 'changelog') && $fullline =~ /^([-+]).*\bFIX(?:ME)\b/) {
        # Break up the string in the regexp above and messages below to avoid
        # this triggering on its own code!
        if ($1 eq '-') {
            # Not an error, but interesting information.
            diagnostic('info', "FIX"."ME removed");
        } else {
            # Not an error, but not good.
            diagnostic('warning', "FIX"."ME added");
        }
    }
    if (defined $lang && ($lang eq 'c++' || $lang eq 'c')) {
        if ($last_line_blank) {
            if ($line_blank) {
                # Allow multiple blank lines at the top level for now.
                diagnostic('error', "Extra blank line") unless ($top_level // 1);
            } elsif (/^.\s+\}$/) {
                # Closing } of a namespace often has a blank line before it,
                # and that seems reasonable.
                diagnostic_last('error', "Blank line at end of block") unless ($top_level // 1);
            } elsif ($penultimate_line_block_start && /^.(\s|\}$)/) {
                diagnostic_last('error', "Blank line at start of block");
            }
        }

        if (/^([-+ ])(\s*)\#/) {
            # Avoid misfiring for something like:
            # #define FOO(x) \
            #     #x
            if (!$preproc_continuation) {
                if ($1 eq '+' && $2 ne '') {
                    diagnostic('error', "Whitespace before '#' on preprocessor line");
                }
            }
            $preproc = 1;
            $preproc_continuation = /\\$/;
        } elsif ($preproc_continuation) {
            $preproc_continuation = /\\$/;
        } else {
            $preproc = 0;
        }
        if ($check_space_tab && /^\+( (?:|  |    |      ))[^ \t].*(?:[^)];|[^);,])\n/) {
            # We only check for 1, 3, 5 and 7 space indents to avoid false
            # positives for "public:", etc and for wrapped expressions.
            #
            # Exclude lines ending ');', ')', or ',' to avoid reporting for
            # wrapped function arguments.  This means we'll also miss some
            # cases we should complain about, but it's likely that at least
            # one line in a mis-indented block will trigger an error.

            # Exclude potential comment continuation lines which might have
            # been missed by the comment stripping code.  Require whitespace
            # after so we flag a mis-indented: *ptr = foo;
            if (!/^\+\s*\*\s/) {
                diagnostic('error', "line indented by ".length($1)." spaces");
            }
        }

        #if (/^\+.*(?<!\btypedef )\b([A-Za-z_][A-Za-z_0-9]*)\s+\(/ &&
        if (/^\+.*\b([A-Za-z_][A-Za-z_0-9]*)\s+\(((?:[A-Za-z][A-Za-z0-9_]*::)?\*|[A-Za-z][A-Za-z0-9_]*\)\()?/) {
            my $name = $1;
            my $post = $2;
            if (
                # `delete (*i)->foo();` rather than `delete(*i)->foo()'` - the `(`
                # isn't around function parameters here.
                $name !~ /^(case|catch|delete|double|for|if|return|switch|throw|while)$/ &&
                # Function pointer type `int (*)(void)` or parenthesised
                # function name `int (foo)(`.
                !($name =~ /^(?:bool|double|float|unsigned|void|[a-z][a-z0-9_]+_t|(?:(?:un)?signed\s+)?(?:char|int|long|short))$/ && length($post))) {
                if (!$preproc) {
                    diagnostic('error', "Whitespace between '$name' and '('");
                } else {
                    # FIXME: We skip preprocessor lines for now to avoid triggering
                    # on things like «#define FOUR (4)» but it would be good to
                    # catch «#define FOO(x) foo (x)»
                }
            }
        }
        if (m!^\+\s*(case|class|do|for|if|namespace|struct|switch|try|union)\b([^ ]| \s)!) {
            diagnostic('error', "'$1' not followed by exactly one space");
        }
        if (m!^\+.*;[^\s\\]!) {
            diagnostic('error', "Missing space after ';'");
        }
        if (m!^\+.*[^(;]\s;!) {
            # Stuff like this is OK: for ( ; ; ) {
            # though for that exact case I'd suggest: while (true) {
            diagnostic('error', "Whitespace before ';'");
        }
        if (m!^\+.*?<<"!) {
            diagnostic('error', "Missing space after '<<'");
        }
        if (m!^\+.*?"<<!) {
            diagnostic('error', "Missing space before '<<'");
        }
        if (m!^\+.*?\b(return)\b([^ ;]| \s)!) {
            diagnostic('error', "'$1' not followed by exactly one space");
        }
        if (m!^\+.*?\b(else)\b([^ \n]| \s)!) {
            diagnostic('error', "'$1' not followed by exactly one space");
        }
        if (m!^\+.*?\b(catch|while)\b([^ ]| \s)!) {
            diagnostic('error', "'$1' not followed by exactly one space");
        }
        if (m!^\+.*?(?:}|}\s{2,}|}\t|^[^}]*)\b(catch)\b!) {
            diagnostic('error', "'$1' not preceded by exactly '} '");
        }
        if (m!^\+.*?(?:}|}\s{2,}|}\t)\b(else|while)\b!) {
            diagnostic('error', "'}' and '$1' not separated by exactly one space");
        }
        if (m,^\+.*?\belse\b\s*(?!if)[^\s{],) {
            diagnostic('error', "Code after 'else' on same line");
        }
        if (m,^\+.*?\belse\s+if.*;\s*$,) {
            diagnostic('error', "Code after 'else if' on same line");
        }
        if (m!^\+.*\((?: [^;]|\t)!) {
            # Allow: for ( ; i != 10; ++i)
            diagnostic('error', "Whitespace after '('");
        }
        if (m!^\+.*\H.*\h\)!) {
            diagnostic('error', "Whitespace before ')'");
        }
        if (m!^\+.*;\s*(\w+)([-+]{2})\)!) {
            diagnostic('error', "Prefer '$2$1' to '$1$2'");
        }
        if (m!^\+.*?>\s+>!) {
            diagnostic('error', "We assume C++11 so can write '>>' instead of '> >'");
        }
        if (m!^\+.*?\b(?:enable_if|list|map|multimap|multiset|priority_queue|set|template|unordered_map|unordered_set|vector)\s+<!) {
            diagnostic('error', "Whitespace between template name and '<'");
        }
        if (/^\+.*?\bfor\s*\([^(]*([^:(]:[^:])/ && $1 ne ' : ') {
            diagnostic('error', "Missing spaces around ':' in 'for'");
        }
        if (m,^\+.*?[\w)](?!-[->]|\+\+)((?:\&\&|\|\||<<|>>|[-+/*%~=<>!&|^])=?|[?]),) {
            my @pre = @-;
            my @post = @+;
            my $op = $1;
            if (substr($_, $pre[1] - 8, 8) eq 'operator') {
                # operator*() etc
            } elsif ($op eq '>' && substr($_, 0, $pre[1]) =~ /[A-Za-z0-9_]</) {
                # y = static_cast<char>(x);
            } elsif ($op eq '>') {
            } elsif ($op eq '<' && substr($_, $pre[1] - 1, 1) =~ /^[A-Za-z0-9_]$/ && substr($_, $post[1]) =~ />/) {
                # y = static_cast<char>(x);
            } elsif ($op eq '<' &&
                     substr($_, 0, $pre[1]) =~ /\b(?:enable_if|list|map|multimap|multiset|priority_queue|set|template|unordered_map|unordered_set|vector)$/) {
                # y = priority_queue<Foo*,
                #                    Bar>;
                # template<typename A,
                #          typename B>
            } elsif ($op eq '&&' && substr($_, 0, $pre[1]) =~ /\b(?:auto|bool|char|double|float|int(?:\d+_t)?|long|short|string|uint\d+_t|unsigned|void|[A-Z][A-Za-z0-9_]*)$/) {
                # auto&& x;
                # method(Class&& foo);
            } elsif (($op eq '<<' || $op eq '>>') &&
                substr($_, 0, $pre[1]) =~ /\b(?:0x[0-9a-fA-F]+|[0-9]+)$/ &&
                substr($_, $post[1]) =~ /^(?:0x[0-9a-fA-F]+|[0-9]+)\b/) {
                # 0x00b1<<26
            } elsif (($op eq '-' || $op eq '+') &&
                substr($_, 0, $pre[1]) =~ /[0-9]\.?e$/) {
                # 1.2e-3, 7.e+3
            } elsif ($op eq '>>' &&
                /[A-Za-z0-9_]<.+</) {
                # vector<vector<int>> v;
            } elsif ($op =~ /^[*&|]$/ &&
                     substr($_, 0, $pre[1]) !~ /(?:\b\d+)\s*$/) {
                # FIXME: *: const char* x;
                # FIXME: &: const char& x;
                # FIXME: |: FOO|BAR
                # (but we do catch "1234*x"
            } elsif ($preproc && /^.\s*#\s*(?:include|error|warning)\b/) {
                # Don't warn about missing whitespace in:
                # #include <a/b-c.h>
                # #error nothing works!
            } else {
                diagnostic('error', "Missing space before '$op'");
            }
        }
        if ($first_char eq '+' && length($_)) {
            # Replace leading `+` to avoid parsing as an operator or part of an
            # operator.
            my $l = ' ' . substr($_, 1);
            # Treat some operator combinations as a single pseudo-operator:
            # x &=~ y;
            # a = b &~ c;
            while ($l =~ m@((?:\|\||<<|>>|[=!/*%<>|^~])=?|-[-=>]?|&[&=]?~?|\+[\+=]?|::?|[?,])@g) {
                my @pre = @-;
                my @post = @+;
                my $op = $1;
                my $prech = substr($l, $pre[1] - 1, 1);
                my $postch = substr($l, $post[1], 1) // '';
                if ($lang eq 'c++' &&
                    ($op eq '*' || $op eq '&') &&
                    (
                     # `vector<some_type *> x;` `int f(some_type *);`
                     (($postch eq '>' || $postch eq ')') && $prech =~ /[ \t]/) ||
                     # `vector<int>*` `string&` `const foo*` `struct tm*` `Xapian::docid&`
                     # +static_assert(Xapian::DB_READONLY_ & Xapian::DB_NO_TERMLIST,
                     (
                      substr($l, 0, $pre[1]) =~ /(?:>|\b(?:auto|bool|char|const|double|float|int(?:\d+_t)?|long|short|string|uint\d+_t|unsigned|void|DIR|DWORD|FD|FILE|HANDLE|WSAOVERLAPPED|[A-Z][A-Z_]*_T|[A-Z]|[A-Z][A-Z0-9_]*?[a-z][A-Za-z0-9_]*|size_type|(?:(?:const|struct)\s+?|Xapian::)[A-Z]*[a-z][A-Za-z0-9_]*)[*&]*)\s+$/ &&
                      substr($l, $post[1]) !~ /^\s*\(/
                     )
                    )
                   ) {
                    diagnostic('error', "Preferred style is 'int$op x' (not 'int ${op}x' or 'int ${op} x')");
                } elsif ($op eq '::') {
                    if ($lang eq 'c++' && $postch =~ /\s/) {
                        diagnostic('error', "Whitespace not expected after '::'");
                    }
                } elsif ($op eq '->' && $prech !~ /\s/) {
                    # a->b
                    # but not:
                    # auto f() -> bool
                    if ($postch =~ /[ \t]/) {
                        diagnostic('error', "Whitespace not expected after '->'");
                    }
                } elsif (($op eq '++' || $op eq '--') && $prech !~ /[A-Za-z0-9_)]/) {
                    # ++a
                    if ($postch =~ /[ \t]/) {
                        diagnostic('error', "Whitespace not expected after '$op'");
                    }
                } elsif ($op eq '!') {
                    # !a
                    if ($postch =~ /[ \t]/) {
                        diagnostic('error', "Whitespace not expected after '!'");
                    }
                } elsif (substr($l, $post[1]) !~ /^(?:\S| \s)/) {
                    # Check what follows the operator.
                } elsif (($op eq '++' || $op eq '--') && $postch =~ /[\]),;]/) {
                    # buf[len++] = 'a';
                    # f(x++);
                    # f(1, x++);
                    # a = b++;
                } elsif (($op eq '-' || $op eq '+' || $op eq '!' || $op eq '~') &&
                    substr($l, 0, $pre[1]) =~ m@(?:^\s*|[-+/*%~=<>&|,;?:] |[\[(]|\b(?:return|case) |^\+\s*)$@) {
                    # Unary -, +, !, ~: e.g. foo = +1; bar = x * (-y); baz = a * -b;
                } elsif ($op eq ',' && (
                    /\b(?:AssertRel(?:Paranoid)?|TEST_REL)\(/ ||
                    /{[^()]*}/)) {
                    # AssertRel(a,<,b);
                } elsif ($op eq '>>' &&
                    /[A-Za-z0-9_]<.+</) {
                    # vector<vector<int>>&
                } elsif ($op eq '*' &&
                         substr($l, 0, $pre[1]) !~ /(?:\b\d+)\s*$/ &&
                         !($lang eq 'c++' &&
                           substr($l, 0, $pre[1]) =~ /(?:>|\b(?:auto|bool|char|const|double|float|int(?:\d+_t)?|long|short|string|uint\d+_t|unsigned|void|[A-Z][A-Za-z0-9_]*|(?:struct\s*?|Xapian::)[a-z][a-z0-9_]*)[*&]*)\s+$/)) {
                    # FIXME: *ptr (dereference)
                    # (but we do catch "1234 *x" and common pointer types etc)
                } elsif ($op eq '&' &&
                         substr($l, 0, $pre[1]) !~ /(?:\b\d+|[^*]\))\s*$/ &&
                         !($lang eq 'c++' &&
                           substr($l, 0, $pre[1]) =~ /(?:>|\b(?:auto|bool|char|const|double|float|int(?:\d+_t)?|long|short|string|uint\d+_t|unsigned|void|[A-Z][A-Za-z0-9_]*|(?:struct\s*?|Xapian::)[a-z][a-z0-9_]*)[*&]*)\s+$/)) {
                    # FIXME: &foo (address of)
                    # (but we do catch "...) &FLAG_FOO" and "1234 &x" and common reference types etc)
                } elsif ($op eq '&&' && $postch =~ /[,)]/) {
                    # int f(int&&, bool&&);
                } elsif ($op =~ /^[<|]$/ &&
                         substr($l, $post[1]) !~ /^\s*(?:\d+\b|\()/ &&
                         substr($l, 0, $pre[1]) !~ /(?:\b\d+|\))\s*$/) {
                    # FIXME: <: std::vector<std::string>
                    # (but we do catch "...) <foo" and "1234 >bar" etc)
                    # FIXME: |: FOO|BAR
                } elsif (substr($l, $pre[1] - 8, 8) eq 'operator' && $postch eq '(') {
                    # operator==() etc
                } elsif (($op eq '<<' || $op eq '>>') &&
                    substr($l, 0, $pre[1]) =~ /\b(?:0x[0-9a-fA-F]+|[0-9]+)$/ &&
                    substr($l, $post[1]) =~ /^(?:0x[0-9a-fA-F]+|[0-9]+)\b/) {
                    # 0x00b1<<26
                } elsif (($op eq '-' || $op eq '+') &&
                    substr($l, 0, $pre[1]) =~ /[0-9]\.?e$/) {
                    # 1.2e-3, 7.e+3
                } elsif ($preproc && $op eq ',') {
                    # Currently there's a lot of: #define FOO(A,B) ...
                } elsif ($preproc && /^.\s*#\s*(?:include|error|warning|pragma)\b/) {
                    # Don't warn about missing whitespace in:
                    # #include <a/b-c.h>
                    # #warning so-so
                    # #pragma warning(disable:4146)
                } elsif ($op eq '>' && ($postch =~ /[,)(;*&\\]/ || substr($l, $post[1], 2) eq '::')) {
                    # int f(vector<int>, vector<int>);
                    # static_cast<char>(7)
                    # return tmpl<true>;
                    # vector<int>* x;
                    # vector<int>& y;
                    # template<class S>\
                    # vector<int>::size_type
                } elsif ($op eq '=' && $postch =~ /[,\]]/) {
                    # Lambdas, e.g. [=]() {...} or [=, &a]() {...}
                } elsif ($op eq '%' && $ext eq 'lemony' && $pre[1] == 1) {
                    # %-directive in Lemon grammar, e.g.:
                    # %left OR.
                } elsif ($op =~ /^([<>]|[<>=!]=)$/ && substr($l, 0, $pre[1]) =~ /\b(?:AssertRel(?:Paranoid)?|TEST_REL)\(/) {
                    # AssertRel(a,>=,b);
                    # TEST_REL(a,>=,b);
                } elsif ($op eq '~' && $postch =~ /[A-Za-z0-9_]/ && substr($l, 0, $pre[1]) =~ /(?:\s|::)$/) {
                    # ~Foo()
                    # Foo::~Foo()
                } elsif ($op eq '>>' && $prech eq '<') {
                    # std::map<std::string, int, std::less<>>*
                } else {
                    # Don't complain about this if it's actually whitespace at
                    # line end.
                    if (substr($l, $post[1]) !~ /^\s*$/) {
                        diagnostic('error', "Should have exactly one space after '$op'");
                    }
                }
            }
        }
        if (/^\+.*;;\s*$/) {
            diagnostic('error', "Extra ';' at end of line");
        }
        if (/^\+\s*?\S.*? (,|->)/) {
            diagnostic('error', "Space before '$1'");
        }
        if (/^\+[\s#]*?[^\s#]  /) {
            # Allow multiple spaces in "#  ifdef FOO".
            diagnostic('error', "Multiple spaces");
        }
        if (/^\+\s*#\s*include([<"])/) {
            # #include<foo.h> or #include"foo.h"
            diagnostic('error', "Missing space between #include and '$1'");
        }
        if (m!^\+(?:.*[;{])?\s*/[/*]{1,2}\w!) {
            diagnostic('error', "added/changed line has comment without whitespace before the text");
        }
        if (m!^\+.*?\)\{!) {
            diagnostic('error', "No space between ')' and '{'");
        }
        if (m!^\+.*?\bconst\{!) {
            diagnostic('error', "No space between 'const' and '{'");
        }
        if ($fnm !~ m!/(?:md5|posixy_wrapper|perftest)\.cc$! &&
            m,^\+.*[^\w\.>]([a-z][a-z0-9]*[A-Z]\w*),) {
            my $symbol = $1;
            my $symbol_idx = $-[1];
            if ($ext eq 'lemony' && $symbol =~ /^yy/) {
                # Used in lemon parser grammar.
            } elsif ($symbol =~ /^[gs]et[A-Z]$/) {
                # For now, allow setD(), etc.
            } elsif ($symbol =~ /^h(?:File|Read|Write|Pipe|Client)$/ || $symbol eq 'fdwCtrlType' || $symbol eq 'pShutdownSocket') {
                # Platform specific names, allow for now.
            } elsif ($symbol eq 'gzFile' || $symbol eq 'uInt' || $symbol =~ /^(?:de|in)flate[A-Z]/) {
                # zlib API uses camelCase names.
            } elsif ($symbol =~ /^pix[A-Z]/) {
                # Tesseract's leptonica image library uses camelCase names.
            } elsif (substr($_, 0, $symbol_idx) =~ /\bicu::(\w+::)?$/) {
                # ICU library namespace uses camelCase method names.
            } elsif (substr($_, 0, $symbol_idx) =~ /\b(?:Abi|CDR|EBOOK|Etonyek|MWAW|RVNG)\w+::$/) {
                # Libabw/Libe-book/libcdr/libetonyek/libmwaw/librevenge use camelCase method names.
            } else {
                diagnostic('error', "camelCase identifier '$symbol' - Xapian coding convention is to use lower case and underscores for variables and functions, and CamelCase for class names");
            }
        }
        if (/^\+.*\b(?:class|struct)\b.*:\s*$/) {
            diagnostic('error', "Inheritance list split after ':', should be before");
        }
        # Try to distinguish ternary operator (?:) correctly split after ":" vs
        # constructor initialiser list incorrectly split after ":".
        my $last_in_ternary = $in_ternary;
        $in_ternary = / \?(?: |$)/;
        if (!$last_in_ternary && !$in_ternary && /^\+.*\)\s*:\s*$/) {
            diagnostic('error', "Constructor initialiser list split after ':', should be before");
        }
        if (m,^\+\s+([-+/%^]|[&|]{2})\s,) {
            diagnostic('error', "Expression split before operator '$1', should be after");
        }
        if ($lang eq 'c++' && /^\+\s+inline\b/) {
            diagnostic('error', "Method defined inside a class is implicitly 'inline'");
        }
        if ($header) {
            if (/^\+using\s+namespace\b/) {
                diagnostic('error', "Avoid 'using namespace' at top level of header");
            }
            if (m!^\+\s*#\s*(ifndef|define|endif\s*/[*/])\s+((?:[A-Z]+_INCLUDED)?_?\w+_[Hh]\b)!) {
                my ($type, $guard) = ($1, $2);
                my $expected_guard;
                if (!defined $header_guard_macro) {
                    if ($type eq 'ifndef') {
                        $header_guard_macro = [$type, $guard];
                        my $expected_guard = uc $fnm;
                        $expected_guard =~ s![-.]!_!g;
                        my $cut;
                        if (length($expected_guard) > length($guard) &&
                            substr($expected_guard, -length($guard) - 1, 1) eq '/' &&
                            substr($expected_guard, -length($guard)) eq $guard) {
                            $cut = -1;
                        } else {
                            for my $i (1 .. length($guard)) {
                                my $ch_e = substr($expected_guard, -$i, 1);
                                my $ch_g = substr($guard, -$i, 1);
                                next if ($ch_e eq $ch_g);
                                last if ($ch_e ne '/' || $ch_g ne '_');
                                $cut = $i;
                            }
                        }
                        if (!defined $cut) {
                            diagnostic('error', "include guard macro should match filename");
                        }
                        my $prefix = 'XAPIAN_INCLUDED_';
                        if ($fnm =~ m!.*omega/(?:.*/)?!) {
                            $prefix = 'OMEGA_INCLUDED_';
                        }
                        #} elsif ($fnm =~ s!.*xapian-core/.*/!!) {
                        # $expected_guard = "XAPIAN_INCLUDED_" . $expected_guard;
                        #} elsif ($fnm =~ s!.*xapian-letor/.*/!!) {
                        #$expected_guard = "XAPIAN_INCLUDED_" . $expected_guard;
                        if (defined $cut && $cut == -1) {
                            diagnostic('error', "include guard macro should use prefix '$prefix'");
                        } elsif (defined $cut && substr($guard, 0, length($guard) - $cut + 1) ne $prefix) {
                            diagnostic('error', "include guard macro should use prefix '$prefix'");
                        } elsif ($guard !~ /^\Q$prefix\E/) {
                            diagnostic('error', "include guard macro should use prefix '$prefix'");
                        }
                    }
                } else {
                    if (!($type eq 'define' && $header_guard_macro->[0] ne 'ifndef')) {
                        my $expected_guard = $header_guard_macro->[1];
                        $header_guard_macro->[0] = $type;
                        if ($guard ne $expected_guard) {
                            diagnostic('error', "include guard macro should be $expected_guard");
                        }
                    }
                }
            }
        } else {
            if (m!^\+\s*#\s*define\s+[A-Z]\+_INCLUDED_!) {
                diagnostic('error', "include guard macro defined in non-header");
            }
        }

        if (defined $last_line_block_end &&
            /^\+${last_line_block_end}(catch|else)\b/) {
            # FIXME: while in do { ... } while can't be as easily checked.
            diagnostic('error', "'$1' should be on same line as preceding '}'");
        }
    } elsif (defined $lang && $lang eq 'py') {
        if (/^\+.*;\s*$/) {
            diagnostic('error', "';' at end of line of python code");
        }
    } elsif (defined $lang && $lang eq 'rb') {
        if (/^\+.*;\s*$/) {
            diagnostic('error', "';' at end of line of ruby code");
        }
    } elsif (defined $lang && $lang eq 'make') {
        if (/^\+.*[A-Za-z0-9)}]  +\s*$/) {
            diagnostic('error', "multiple spaces in Makefile");
        }
    }
    if (defined $fnm && $fnm !~ m!xapian-check-patch|ChangeLog|NEWS|stemming/.*/(?:voc2?|output2?)\.txt$|omega/testfiles/|unicode/UnicodeData\.txt!) {
        if ($fullline =~ /^\+.*?(?:\b|_)(xapain|the the|initialsing|ipv5|outputing|intened|wull|extrac|if it possible|betweem|differen|auxiliar|wat(?:|ed|ing|s)|wth|teh|ned|incase)(?:\b|_)/i ||
            # Cases which just need to be the prefix of a word
            $fullline =~ /^\+.*?(?:\b|_)((?:additon|deafult|parm|peform|acessor|comptib|seach|seperat|seprat|separater|iteratat|calulat|delimitor|delimeter|charactor|databse|operatoar|implict|differnt|orignal|straterg|unecessar|comamnd|docuemnt|implment|initilias|capatil|reprensent|ommit|openning|openned|appropirate|labrar|returm|interati|termfrequenc|continous|juding|gradinet|clearling|clearled|retreiv|reteriv|filedescriptor|avalil*ab|assessem|contruct|particlar|revelan|releven|relv|intial|eal|specifiy|(?:tera|mega|kilo)?btye|comunic|accumlat|useage|existant|regrex|next(?!step)[eis])[a-z]*(?:\b|_))/i ||
            # Case-sensitive cases
            $fullline =~ /^\+.*?\b(and and|dont|Dont)\b/) {
            diagnostic('error', "Typo '$1'");
        }
    }

    if ($check_indent) {
        # Check indentation.
        if (defined $indent && $first_char eq '+' &&
            # blank
            !/^\+\s*$/ &&
            # Preprocessor line
            !$preproc &&
            # Label for goto
            !/^\+[A-Za-z_][A-Za-z_0-9]*:/ &&
            # outdent
            !/^\+\s*}/) {
            # Special handling for access specifiers, which should get a half indent.
            if (/^\+\s*(?:private|protected|public):/) {
                $indent -= 2;
            } elsif ($case_no_brace && /^\+(?:[ \t]*)(?:case\b.*|default):(?:\s*\{)?$/) {
                # case or default following a case or default without a '{', so
                # shouldn't be indented - reduce $indent by 4 columns.
                $indent -= 4;
            }
            my $this_indent = 0;
            if ($fullline =~ /^.([ \t]+)/) {
                $this_indent = count_columns($1);
            }
            my $extra = $this_indent - $indent;
            if ($extra) {
                my $which = 'over';
                if ($extra < 0) {
                    $extra = -$extra;
                    $which = 'under';
                }
                my $s = '';
                $s = 's' if $extra > 1;
                diagnostic('error', "Line ${which}indented by $extra column$s");
            }
        }

        #if (/^[-+ ]([ \t]*)(?:(?:(?:catch|for|if|for|switch|while)\b.*\)|(?:case|class|do|else|struct|try|union)\b.*) \{|case\b.*:)$/) {
        if (/^[+ ]([ \t]*)(?:(catch|for|if|for|while|case|class|default|do|else|struct|try|union)\b.* \{|(case\b.*|default):)$/) {
            $indent = count_columns($1);
            my $keyword = $2 // $3;
            $case_no_brace = $3;
            # FIXME: Might be OK in e.g. lambdas
            #if (/^\+/ && $indent % 4 != 0) {
            #    diagnostic('error', "Indented by $len columns - not a multiple of 4");
            #}
            $indent += $keyword =~ /^(?:case|switch|default)/ ? 2 : 4;
        } elsif (/^[-+ ]([ \t]*)(?:(?:private|protected|public):)$/) {
            # Access specifiers get a half indent and are followed by another half indent.
            $indent = count_columns($1);
            $case_no_brace = undef;
            if (/^\+/ && $indent % 4 != 2) {
                diagnostic('error', "Indented by $indent columns, should be 2 plus a multiple of 4");
            }
            $indent += 2;
        } elsif (!/^.\s*$/) {
            # Only reset for a non-blank line (after comment removal).
            $indent = undef;
            $case_no_brace = undef;
        }
    }

    if ($first_char eq ' ') {
        ++$lineno;
    } elsif ($first_char eq '+') {
        ++$lineno;
        ++$add_lines;
    } elsif ($first_char eq '-') {
        ++$del_lines;
    } elsif ($first_char eq '\\') {
        # "\ No newline at end of file" - if preceded by a "+" line, this means
        # that the patch leaves the file missing a newline at the end.
        if ($check_end_new_line && $last_first_char eq '+') {
            diagnostic_last('error', 'No newline at end of file');
        }
    }
    $last_fullline = $fullline;
    $last_first_char = $first_char;
    $last_line_blank = $line_blank;
    if (/^.([ \t]+)\}$/) {
        $last_line_block_end = $1;
    } else  {
        $last_line_block_end = undef;
    }
    $penultimate_line_block_start = $last_line_block_start;
    if (/^.(.*\{)\s*$/) {
        $last_line_block_start = $1;
    } else {
        $last_line_block_start = undef;
    }
}
if (scalar keys %count) {
    for (sort keys %count) {
        print STDERR "$_ count:\t$count{$_}\n";
    }
    print STDERR "\n";
}
print STDERR <<"__END__";
Files patched:\t$files
Lines added:\t$add_lines
Lines removed:\t$del_lines
__END__

exit 0 unless exists $count{'error'};

if (exists $ENV{GITHUB_JOB} || exists $ENV{TRAVIS}) {
    print STDERR <<"__END__";

You can run these checks locally before pushing with the xapian-check-patch
which is in the source tree in the xapian-maintainer-tools directory.

E.g. to check any changes in your working directory which aren't on master:

git diff master.. | xapian-maintainer-tools/xapian-check-patch
__END__
}

exit 1;