Malloc Tracing

I recently had to use this feature to find a memory leak in some code I was debugging.

Including in your code

You need to add the following into your #include section of your code:

#include <mtrace.h>

 This includes the malloc tracing headers. in your main() function, add the following near the top of the function:

int main(int argc, char *argv[])
{
    ...
    mtrace();
    ...
    ...
}

 Setting up the Environment for Tracing

After your program is compiled, you need to specify where the tracing file is located. Export the following variable before launching your program:

export MALLOC_TRACE="/tmp/mtrace.txt"

 Using mtrace.pl

I had to dig around to find this, but this perl script will go through and extrapolate which malloc calls are not freed and print a list of them.

Here is a sample of the output of mtrace

 Mtrace Source Code

#! /usr/bin/perl
#eval "exec /usr/bin/perl -S $0 $*"
#    if 0;
# Copyright (C) 1997-2002, 2003, 2004 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
# Contributed by Ulrich Drepper <drepper@gnu.org>, 1997.
# Based on the mtrace.awk script.
 
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
 
# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
 
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, write to the Free
# Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
# 02111-1307 USA.
 
$VERSION = "2.3.6";
$PACKAGE = "libc";
$progname = $0;
 
sub usage {
    print "Usage: mtrace [OPTION]... [Binary] MtraceDatan";
    print "  --help       print this help, then exitn";
    print "  --version    print version number, then exitn";
    print "n";
    print "For bug reporting instructions, please see:n";
    print "<http://www.gnu.org/software/libc/bugs.html>.n";
    exit 0;
}
 
# We expect two arguments:
#   #1: the complete path to the binary
#   #2: the mtrace data filename
# The usual options are also recognized.
 
arglist: while (@ARGV) {
    if ($ARGV[0] eq "--v" || $ARGV[0] eq "--ve" || $ARGV[0] eq "--ver" ||
	$ARGV[0] eq "--vers" || $ARGV[0] eq "--versi" ||
	$ARGV[0] eq "--versio" || $ARGV[0] eq "--version") {
	print "mtrace (GNU $PACKAGE) $VERSIONn";
	print "Copyright (C) 2005 Free Software Foundation, Inc.n";
	print "This is free software; see the source for copying conditions.  There is NOn";
	print "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.n";
	print "Written by Ulrich Drepper <drepper@gnu.org>n";
 
	exit 0;
    } elsif ($ARGV[0] eq "--h" || $ARGV[0] eq "--he" || $ARGV[0] eq "--hel" ||
	     $ARGV[0] eq "--help") {
	&usage;
    } elsif ($ARGV[0] =~ /^-/) {
	print "$progname: unrecognized option `$ARGV[0]'n";
	print "Try `$progname --help' for more information.n";
	exit 1;
    } else {
	last arglist;
    }
}
 
if ($#ARGV == 0) {
    $binary="";
    $data=$ARGV[0];
} elsif ($#ARGV == 1) {
    $binary=$ARGV[0];
    $data=$ARGV[1];
 
    if ($binary =~ /^.*[/].*$/) {
	$prog = $binary;
    } else {
	$prog = "./$binary";
    }
    if (open (LOCS, "env LD_TRACE_LOADED_OBJECTS=1 $prog |")) {
	while (<LOCS>) {
	    chop;
	    if (/^.*=> (.*) .(0x[0123456789abcdef]*).$/) {
		$locs{$1} = $2;
	    }
	}
	close (LOCS);
    }
} else {
    die "Wrong number of arguments, run $progname --help for help.";
}
 
sub location {
    my $str = pop(@_);
    return $str if ($str eq "");
    if ($str =~ /.*[[](0x[^]]*)]:(.)*/) {
	my $addr = $1;
	my $fct = $2;
	return $cache{$addr} if (exists $cache{$addr});
	if ($binary ne "" && open (ADDR, "arm-linux-addr2line -e $binary $addr|")) {
	    my $line = <ADDR>;
	    chomp $line;
	    close (ADDR);
	    if ($line ne '??:0') {
		$cache{$addr} = $line;
		return $cache{$addr};
	    }
	}
	$cache{$addr} = $str = "$fct @ $addr";
    } elsif ($str =~ /^(.*):.*[[](0x[^]]*)]$/) {
	my $prog = $1;
	my $addr = $2;
	my $searchaddr;
	return $cache{$addr} if (exists $cache{$addr});
	if ($locs{$prog} ne "") {
	    $searchaddr = sprintf "%#x", $addr - $locs{$prog};
	} else {
	    $searchaddr = $addr;
	    $prog = $binary;
	}
	if ($binary ne "" && open (ADDR, "arm-linux-addr2line -e $prog $searchaddr|")) {
	    my $line = <ADDR>;
	    chomp $line;
	    close (ADDR);
	    if ($line ne '??:0') {
		$cache{$addr} = $line;
		return $cache{$addr};
	    }
	}
	$cache{$addr} = $str = $addr;
    } elsif ($str =~ /^.*[[](0x[^]]*)]$/) {
	my $addr = $1;
	return $cache{$addr} if (exists $cache{$addr});
	if ($binary ne "" && open (ADDR, "addr2line -e $binary $addr|")) {
	    my $line = <ADDR>;
	    chomp $line;
	    close (ADDR);
	    if ($line ne '??:0') {
		$cache{$addr} = $line;
		return $cache{$addr};
	    }
	}
	$cache{$addr} = $str = $addr;
    }
    return $str;
}
 
$nr=0;
open(DATA, "<$data") || die "Cannot open mtrace data file";
while (<DATA>) {
    my @cols = split (' ');
    my $n, $where;
    if ($cols[0] eq "@") {
	# We have address and/or function name.
	$where=$cols[1];
	$n=2;
    } else {
	$where="";
	$n=0;
    }
 
    $allocaddr=$cols[$n + 1];
    $howmuch=hex($cols[$n + 2]);
 
    ++$nr;
    SWITCH: {
	if ($cols[$n] eq "+") {
	    if (defined $allocated{$allocaddr}) {
		printf ("+ %#010x Alloc %d duplicate: %s %sn",
			hex($allocaddr), $nr, &location($addrwas{$allocaddr}),
			$where);
	    } else {
		$allocated{$allocaddr}=$howmuch;
		$addrwas{$allocaddr}=$where;
	    }
	    last SWITCH;
	}
	if ($cols[$n] eq "-") {
	    if (defined $allocated{$allocaddr}) {
		undef $allocated{$allocaddr};
		undef $addrwas{$allocaddr};
	    } else {
		printf ("- %#010x Free %d was never alloc'd %sn",
			hex($allocaddr), $nr, &location($where));
	    }
	    last SWITCH;
	}
	if ($cols[$n] eq "<") {
	    if (defined $allocated{$allocaddr}) {
		undef $allocated{$allocaddr};
		undef $addrwas{$allocaddr};
	    } else {
		printf ("- %#010x Realloc %d was never alloc'd %sn",
			hex($allocaddr), $nr, &location($where));
	    }
	    last SWITCH;
	}
	if ($cols[$n] eq ">") {
	    if (defined $allocated{$allocaddr}) {
		printf ("+ %#010x Realloc %d duplicate: %#010x %s %sn",
			hex($allocaddr), $nr, $allocated{$allocaddr},
			&location($addrwas{$allocaddr}), &location($where));
	    } else {
		$allocated{$allocaddr}=$howmuch;
		$addrwas{$allocaddr}=$where;
	    }
	    last SWITCH;
	}
	if ($cols[$n] eq "=") {
	    # Ignore "= Start".
	    last SWITCH;
	}
	if ($cols[$n] eq "!") {
	    # Ignore failed realloc for now.
	    last SWITCH;
	}
    }
}
close (DATA);
 
# Now print all remaining entries.
@addrs= keys %allocated;
$anything=0;
if ($#addrs >= 0) {
    foreach $addr (sort @addrs) {
	if (defined $allocated{$addr}) {
	    if ($anything == 0) {
		print "nMemory not freed:n-----------------n";
		print ' ' x (10 - 7), "Address     Size     Callern";
		$anything=1;
	    }
	    printf ("%#010x %#8x  at %sn", hex($addr), $allocated{$addr},
		    &location($addrwas{$addr}));
	}
    }
}
print "No memory leaks.n" if ($anything == 0);
 
exit $anything != 0;