#!/usr/bin/perl
# Detect instances of "if (p) free (p);".
# Likewise for "if (p != NULL) free (p);".
# Exit status is like grep: 0 for no match. 1 for any number.

# Note: giving line numbers isn't practical, since I've reset the
# input record separator.
use strict;
use warnings;
(my $ME = $0) =~ s|.*/||;

{
  # Use ';' as the input record separator.
  $/ = ';';

  my $found_match = 0;
  foreach my $file (@ARGV)
    {
      open FH, '<', $file
	or die "$ME: can't open `$file' for reading: $!\n";
      while (defined (my $line = <FH>))
	{
	  if ($line =~
	      /\b(if\s*\(\s*(\S+?)(?:\s*!=\s*NULL)?\s*\)
	       \s+(?:xmlXPathFreeContext|(?:sexpr_)?free)\s*\(\s*\2\s*\))/sx)
	    {
	      print "$file: $1\n";
	      $found_match = 1;
	    }
	}
      close FH;
    }
  exit !$found_match;
}

my $foo = <<'EOF';
# The above is to *find* them.
# This adjusts them, removing the unnecessary "if (p)" part.

git ls-files -z --exclude=find-unnecessary-if-before-free |xargs -0 \
perl -0x3b -pi -e 's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*NULL)?\s*\)\s+((?:xmlXPathFreeContext|(?:sexpr_)?free)\s*\(\s*\1\s*\))/$2/s'
EOF