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Report information
Id: 43633
Status: resolved
Priority: 0/
Queue: perl5

Owner: Nobody
Requestors: steven.pritchard <steve [at] silug.org>
Cc:
AdminCc:

Operating System: Linux
PatchStatus: (no value)
Severity: High
Type: core
Perl Version: 5.8.8
Fixed In: (no value)



Subject: Cwd::cwd() use in File::Spec::Unix use causes unnecessary fork()
Date: Sat, 7 Jul 2007 22:32:37 -0500
To: perlbug [...] perl.org
From: Steven Pritchard <steve [...] osiris.silug.org>
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This is a bug report for perl from steve@silug.org, generated with the help of perlbug 1.35 running under perl v5.8.8. ----------------------------------------------------------------- File::Spec::Unix contains the following code: sub _cwd { require Cwd; Cwd::cwd(); } I think we can safely say that getcwd() will exist on anything Unix-y enough to run File::Spec::Unix, so changing the cwd() to getcwd() would avoid a fork() to run /bin/pwd. This code can apparently end up in a hot code path by using IO::File, which uses File::Spec. In light testing, the following patch seems to work fine: --- perl-5.8.8/lib/File/Spec/Unix.pm.orig 2005-08-27 12:14:38.000000000 -0500 +++ perl-5.8.8/lib/File/Spec/Unix.pm 2007-07-07 22:13:51.000000000 -0500 @@ -470,7 +470,7 @@ # File::Spec subclasses use this. sub _cwd { require Cwd; - Cwd::cwd(); + Cwd::getcwd(); } I've also verified that the above patch applies cleanly to 5.9.5. ----------------------------------------------------------------- --- Flags: category=core severity=high --- This perlbug was built using Perl v5.8.8 in the Red Hat build system. It is being executed now by Perl v5.8.8 - Wed May 16 22:56:53 EDT 2007. Site configuration information for perl v5.8.8: Configured by Red Hat, Inc. at Wed May 16 22:56:53 EDT 2007. Summary of my perl5 (revision 5 version 8 subversion 8) configuration: Platform: osname=linux, osvers=2.6.20-1.2933.fc6xen, archname=x86_64-linux-thread-multi uname='linux xenbuilder3.fedora.phx.redhat.com 2.6.20-1.2933.fc6xen #1 smp mon mar 19 11:17:46 edt 2007 x86_64 x86_64 x86_64 gnulinux ' config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Dversion=5.8.8 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Dprivlib=/usr/lib/perl5/5.8.8 -Dsitelib=/usr/lib/perl5/site_perl/5.8.8 -Dvendorlib=/usr/lib/perl5/vendor_perl/5.8.8 -Darchlib=/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi -Dsitearch=/usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi -Dvendorarch=/usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi -Darchname=x86_64-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_pro to -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dinc_version_list=5.8.7 5.8.6 5.8.5 -Dscriptdir=/usr/bin' hint=recommended, useposix=true, d_sigaction=define usethreads=define use5005threads=undef useithreads=define usemultiplicity=define useperlio=define d_sfio=undef uselargefiles=define usesocks=undef use64bitint=define use64bitall=define uselongdouble=undef usemymalloc=n, bincompat5005=undef Compiler: cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm', optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic', cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -I/usr/include/gdbm' ccversion='', gccversion='4.1.2 20070502 (Red Hat 4.1.2-12)', gccosandvers='' intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16 ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8 alignbytes=8, prototype=define Linker and Libraries: ld='gcc', ldflags ='' libpth=/usr/local/lib64 /lib64 /usr/lib64 libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc libc=, so=so, useshrplib=true, libperl=libperl.so gnulibc_version='2.6' Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi/CORE' cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' Locally applied patches: --- @INC for perl v5.8.8: /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.8.7/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.8.6/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.8.5/x86_64-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl/5.8.7 /usr/lib/perl5/site_perl/5.8.6 /usr/lib/perl5/site_perl/5.8.5 /usr/lib/perl5/site_perl /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.8.7/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.8.6/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.8.5/x86_64-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl/5.8.7 /usr/lib/perl5/vendor_perl/5.8.6 /usr/lib/perl5/vendor_perl/5.8.5 /usr/lib/perl5/vendor_perl /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi /usr/lib/perl5/5.8.8 . --- Environment for perl v5.8.8: HOME=/home/steve LANG=en_US.UTF-8 LANGUAGE (unset) LC_COLLATE=C LD_LIBRARY_PATH (unset) LOGDIR (unset) PATH=/usr/lib64/ccache:/usr/lib64/qt-3.3/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/local/bin:/usr/games:/home/steve/bin PERL_BADLANG (unset) SHELL=/bin/bash
Thanks, applied as #31686 to bleadperl.
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Turns out this caused a bug on OS X and broke the documented interface of File::Spec->rel2abs() which is supposed to use cwd(). See https://rt.cpan.org/Ticket/Display.html?id=47637


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