p5pRT
commented
20 years ago From zokaites@usgs.gov
Title Purify located memory errors
Symptom I just completed an application which showed the existence of memory errors in the Perl language itself. My application formerly hung when shelling out to unix with backticks. When I ran the spawned command from a csh\, it executed quickly. Nonetheless\, my perl application hung at the backticks and did not even start a new unix process (verified with ps). Updating unrelated portions of my application made the hang problem disappear or reappear. This is the kind of inconsistent\, erratic behavior which is typified by memory errors.
Purify build To test for memory errors\, I (partially) built the perl language (perl-5.8.4) with purify. (Purify is a commercial source code library used to locate memory errors in "C".) My host is a SGI ("uname -a" shows "IRIX64 e0spg11 6.5 07121149 IP35"). To enable a purify build\, I changed "cc -n32" to "purify cc -g -n32" in 3 places in config.sh.
Build problems I executed "make ; make test". The build proceeded nicely for a while but then miniperl hung. I aborted that miniperl process and the build continued on. Hundreds of the tests failed\, probably because the build partially failed. The build log shows:
*** lib/auto/DynaLoader/DynaLoader.a removed.
I added "set -vx" to perl-5.8.4/ext/util/make_ext and determined that miniperl hung when it was passed the following command line arguments:
-I../../lib Makefile.PL INSTALLDIRS=perl PERL_CORE=1 LIBPERL_A=libperl.a
I tried to debug miniperl via "dbx ../../miniperl" but received "error in step/next command".
Errors located with purify My partial build identified the following errors:
**** Purify instrumented ./perl (pid 92576237) **** ABR: Array bounds read (2 times): * This is occurring while in: Perl_yyparse [perly.c:1599] S_parse_body [perl.c:1765] perl_parse [perl.c:1270] main [perlmain.c:84] __start [crt1text.s:176] * Reading 4 bytes from 0x101dff18 in the heap. * Address 0x101dff18 is 1 byte past end of a malloc'd block at 0x101dfa68 of 1200 bytes. * This block was allocated from: _malloc [malloc.c:1164] Perl_safesysmalloc [util.c:67] Perl_yyparse [perly.c:1456] S_parse_body [perl.c:1765] perl_parse [perl.c:1270] main [perlmain.c:84]
**** Purify instrumented ./perl (pid 93060130) **** PAR: Bad function parameter: * This is occurring while in: XS_DynaLoader_dl_load_file [DynaLoader.xs:191] Perl_pp_entersub [pp_hot.c:2854] Perl_runops_standard [run.c:24] S_call_body [perl.c:2285] Perl_call_sv [perl.c:2203] S_call_list_body [perl.c:4663] * dlopen("../lib/auto/POSIX/POSIX.so"\, 1) Purify'd file (../lib/auto/POSIX/POSIX.so) not found.
I reported the following error to SGI (the hardware vendor): **** Purify instrumented ./miniperl (pid 92083168) **** UMR: Uninitialized memory read (2 times): * This is occurring while in: _setcontext [syscalls.c:15191] _siglongjmp [siglongjmp.c:46] Perl_vdie [util.c:1108] Perl_die [util.c:1132] Perl_pp_die [pp_sys.c:510] Perl_runops_standard [run.c:24] * Reading 800 bytes from 0x7fff28f0 on the stack (52 bytes at 0x7fff28f4 uninit).
Memory leaks Small memory leaks present no problem for short-running applications (like mine). However\, for applications which run a long time\, memory leaks can gradually consume all the physical and virtual memory on a computer. My purify tests located some memory errors which I haven't reported here for the purposes of brevity.
The next step Does anyone test new perl versions for memory errors? My management will allow me to conduct some memory error testing. Note that my build failed part way through and is therefore not an exhaustive test for memory errors. I'm considering trying for a more complete purify build of perl.
Migrated from rt.perl.org#30043 (status was 'resolved')
Searchable as RT30043$