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[perl #132545] Double macro argument evaluation in S_init_main_stash

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From:
Pip Cet
Date:
December 8, 2017 08:44
Subject:
[perl #132545] Double macro argument evaluation in S_init_main_stash
Message ID:
rt-4.0.24-29248-1512722692-588.132545-75-0@perl.org
# New Ticket Created by  Pip Cet 
# Please include the string:  [perl #132545]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=132545 >


This is a bug report for perl from pipcet@gmail.com,
generated with the help of perlbug 1.41 running under perl 5.27.7.


-----------------------------------------------------------------
[Please describe your issue here]

I just came across the following problem:

S_init_main_stash contains the code:

    PL_curstash = PL_defstash = (HV *)SvREFCNT_inc_simple_NN(newHV());

SvREFCNT_inc_simple_NN is defined as:

#define SvREFCNT_inc_simple_NN(sv)    (++(SvREFCNT(sv)),MUTABLE_SV(sv))

That evaluates its argument twice, which breaks with side effects.

So newHV() is called twice, one of the new HVs gets refcount 2 and
gets leaked, the other gets refcount 1 and gets stored in two
places. I suspect this is low-priority, but there might be a way to
actually destroy the stash while it is still stored in PL_defstash, in
which case it's a user-visible bug.

Sorry if this message gets duplicated, I tried sending it a few days ago
and it appears to have vanished.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.27.7:

Configured by pip at Mon Dec  4 13:27:33 UTC 2017.

Summary of my perl5 (revision 5 version 27 subversion 7) configuration:

  Platform:
    osname=linux
    osvers=4.13.0-1-amd64
    archname=x86_64-linux
    uname='linux amygdala 4.13.0-1-amd64 #1 smp debian 4.13.10-1
(2017-10-30) x86_64 gnulinux '
    config_args=''
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='g++'
    ccflags ='-fwrapv -fno-strict-aliasing -pipe
-fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64 -I/home/pip/git/emacs-c++/js/dist/include
-pthread -g3 -ggdb'
    optimize='-O2'
    cppflags='-fwrapv -fno-strict-aliasing -pipe
-fstack-protector-strong -I/usr/local/include -pthread'
    ccversion=''
    gccversion='8.0.0 20171124 (experimental)'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='ld'
    ldflags =' -fstack-protector-strong -g3 -ggdb -L/usr/local/lib'
    libpth=/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.0.0/../../../../include/c++/8.0.0
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.0.0/../../../../include/c++/8.0.0/x86_64-pc-linux-gnu
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.0.0/../../../../include/c++/8.0.0/backward
/usr/local/lib /usr/local/lib/gcc/x86_64-pc-linux-gnu/8.0.0/include-fixed
/usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu
/lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /lib64
/usr/lib64 /usr/local/lib64
    libs=-lpthread -pthread -lnsl -ldl -lm -lcrypt -lutil -lc
-lmozjs-58a1 -Wl,--whole-archive mozglue.a -Wl,--no-whole-archive
    perllibs=-lpthread -pthread -lnsl -ldl -lm -lcrypt -lutil -lc -L
/home/pip/git/emacs-c++/js/dist/bin -lmozjs-58a1 -Wl,--whole-archive
/home/pip/git/emacs-c++/js/mozglue/build/libmozglue.a
-Wl,--no-whole-archive
    libc=libc-2.25.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.25'
  Dynamic Linking:
    dlsrc=dl_none.xs
    dlext=none
    d_dlsymun=undef
    ccdlflags=''
    cccdlflags=''
    lddlflags=''


---
@INC for perl 5.27.7:
    .
    lib
    /usr/local/lib/perl5/site_perl/5.27.7/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.27.7
    /usr/local/lib/perl5/5.27.7/x86_64-linux
    /usr/local/lib/perl5/5.27.7

---
Environment for perl 5.27.7:
    HOME=/home/pip
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH=/home/pip/git/emacs-c++/js/dist/bin:/home/pip/amd/AMDAPPSDK-3.0/lib/x86_64/
    LOGDIR (unset)
    PATH=/home/pip/.cargo/bin:/home/pip/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/sbin:/usr/local/sbin:/usr/sbin:/sbin:/usr/local/sbin:/usr/sbin
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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