I believe that in those examples, Perl is actually leaking the scalars, along with a lot of other stuff -- look at the "still reachable" stat. It's doing this intentionally, by exiting immediately rather than painstakingly deallocating everything first.
In order to persuade Perl to deallocate everything, you need a Perl compiled with -DDEBUGGING and to set the PERL_DESTRUCT_LEVEL environment variable to 2. You are also likely need to create a Valgrind suppressions file to adapt for miscellaneous noise from libc, Dynaloader, etc.
In the end, though, you still don't see any difference when running those two examples. I would argue that the proof needed tightening up -- but the reasoning and explanation were sound.marvin@smokey:~ $ PERL_DESTRUCT_LEVEL=2 valgrind --show-reachable=yes +--leak-check=full \ > --suppressions=~/debugperl.supp \ > debugperl -e'my $x; $x = \$x; undef $x if $ARGV[0]' 1 ==79872== Memcheck, a memory error detector ==79872== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et +al. ==79872== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright + info ==79872== Command: debugperl -emy\ $x;\ $x\ =\ \\$x;\ undef\ $x\ if\ $ +ARGV[0] 1 ==79872== --79872-- /Users/marvin/bin/debugperl: --79872-- dSYM directory has wrong UUID; consider using --dsymutil=yes ==79872== ==79872== HEAP SUMMARY: ==79872== in use at exit: 94,131 bytes in 12 blocks ==79872== total heap usage: 625 allocs, 613 frees, 219,612 bytes all +ocated ==79872== ==79872== LEAK SUMMARY: ==79872== definitely lost: 0 bytes in 0 blocks ==79872== indirectly lost: 0 bytes in 0 blocks ==79872== possibly lost: 0 bytes in 0 blocks ==79872== still reachable: 0 bytes in 0 blocks ==79872== suppressed: 94,131 bytes in 12 blocks ==79872== ==79872== For counts of detected and suppressed errors, rerun with: -v ==79872== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from +0) marvin@smokey:~ $ PERL_DESTRUCT_LEVEL=2 valgrind --show-reachable=yes +--leak-check=full \ > --suppressions=~/debugperl.supp \ > debugperl -e'my $x; $x = \$x; undef $x if $ARGV[0]' 0 ==79881== Memcheck, a memory error detector ==79881== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et +al. ==79881== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright + info ==79881== Command: debugperl -emy\ $x;\ $x\ =\ \\$x;\ undef\ $x\ if\ $ +ARGV[0] 0 ==79881== --79881-- /Users/marvin/bin/debugperl: --79881-- dSYM directory has wrong UUID; consider using --dsymutil=yes ==79881== ==79881== HEAP SUMMARY: ==79881== in use at exit: 94,131 bytes in 12 blocks ==79881== total heap usage: 625 allocs, 613 frees, 219,612 bytes all +ocated ==79881== ==79881== LEAK SUMMARY: ==79881== definitely lost: 0 bytes in 0 blocks ==79881== indirectly lost: 0 bytes in 0 blocks ==79881== possibly lost: 0 bytes in 0 blocks ==79881== still reachable: 0 bytes in 0 blocks ==79881== suppressed: 94,131 bytes in 12 blocks ==79881== ==79881== For counts of detected and suppressed errors, rerun with: -v ==79881== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from +0) marvin@smokey:~ $
In reply to Re^4: Make Perl use real malloc
by creamygoodness
in thread Make Perl use real malloc
by creamygoodness
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