Bug#47214: dpkg: Memleak in libdpkg when using parseversion() (lib/parsehelp.c)

[<aj@azure.humbug.org.au>]

Package: dpkg
Version: 1.4.1.13
Severity: wishlist

parseversion calls nfstrsave which is a strdup() clone which calls
nfmalloc(), dpkg's non-freeing malloc.

When using a cmpversions() based on dpkg's (see main/enquire.c) in a long
lived process that does a lot of comparisons, all this memory is completely
wasted. The program I'm working loses a good 3MB every 5s or so thanks to
this. (What can I say? I do a lot of version comparisons)

A workaround is to use libapt-pkg's version comparison stuff instead, which
doesn't leak memory in any noticable amount.

Something like:

	#include <apt-pkg/version.h>
	extern "C" {
	int cmpversions(char *left, char *op, char *right) {
		int i = pkgVersionCompare(left, right);
		if (!strcmp(op, "<=")) return i <= 0;
		if (!strcmp(op, ">=")) return i >= 0;
		if (!strcmp(op, "<<")) return i <  0;
		if (!strcmp(op, ">>")) return i >  0;
		if (!strcmp(op, "="))  return i == 0;
	}
	}

in a C++ source file gives similar behaviour to the original (although
it returns 1/0 for true/false (C-style) instead of 0/1 (shell style),
and doesn't handle as many operators, or error conditions).

Cheers,
aj

-- System Information
Debian Release: potato
Kernel Version: Linux azure 2.0.33 #1 Fri May 15 19:45:40 EST 1998 i586 unknown

Versions of the packages dpkg depends on:
ii  libc6           2.1.2-0pre12   GNU C Library: Shared libraries and timezone
ii  libncurses4     4.2-3.2        Shared libraries for terminal handling
ii  libstdc++2.10   2.95.1-1       The GNU stdc++ library