crash in return from lvalue subroutine from try {} block

[tonycoz]

Module:

Description

I was looking again over the pp_return code in reference to #18540, and while I don't see an ordering problem, I do think that the additional code that's doing what dopopto_cursub() should be doing is a bit suspicious.

I looked over what else calls dopopto_cursub(), and ended up with:

$ gdb --args ./perl -Ilib -Mfeature=try -le 'my $x = 0; sub foo :lvalue { try { print "Hello\n"; return %x } catch ($e) { } } foo() = 1; print $x'
...
(gdb) r
Starting program: /home/tony/dev/perl/git/perl4/perl -Ilib -Mfeature=try -le my\ \$x\ =\ 0\;\ sub\ foo\ :lvalue\ \{\ try\ \{\ print\ \"Hello\\n\"\;\ return\ %x\ \}\ catch\ \(\$e\)\ \{\ \}\ \}\ foo\(\)\ =\ 1\;\ print\ \$x
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
try/catch is experimental at -e line 1.
try/catch is experimental at -e line 1.
Hello


Program received signal SIGSEGV, Segmentation fault.
0x00005555558440e9 in Perl_is_lvalue_sub () at pp_ctl.c:1416
1416        if (CxLVAL(cxstack + cxix) && CvLVALUE(cxstack[cxix].blk_sub.cv))
(gdb) bt
#0  0x00005555558440e9 in Perl_is_lvalue_sub () at pp_ctl.c:1416
#1  0x000055555577c005 in Perl_pp_rv2av () at pp_hot.c:1980
#2  0x0000555555721e8d in Perl_runops_debug () at dump.c:2572
#3  0x00005555555f1102 in S_run_body (oldscope=1) at perl.c:2743
#4  0x00005555555f0680 in perl_run (my_perl=0x555555c17260) at perl.c:2666
#5  0x00005555555a2122 in main (argc=5, argv=0x7fffffffe778, 
    env=0x7fffffffe7a8) at perlmain.c:110

I haven't worked out a fix yet, I don't see the segv with #18552 but I don't see anything in that change which I'd expect to fix this problem either.

Steps to Reproduce

see above

Expected behavior

don't crash

Perl configuration

tony@venus:.../git/perl4$ ./perl -Ilib -V
Summary of my perl5 (revision 5 version 33 subversion 7) configuration:
  Commit id: 44898a56694f929002276127c878850373a82481
  Platform:
    osname=linux
    osvers=4.19.0-13-amd64
    archname=x86_64-linux
    uname='linux venus 4.19.0-13-amd64 #1 smp debian 4.19.160-2 (2020-11-28) x86_64 gnulinux '
    config_args='-des -Dusedevel -DDEBUGGING -Doptimize=-O0 -g'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='cc'
    ccflags ='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O0 -g'
    cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='8.3.0'
    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='cc'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/8/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
    libs=-lpthread -lnsl -lgdbm -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.28.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.28'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O0 -g -L/usr/local/lib -fstack-protector-strong'


Characteristics of this binary (from libperl): 
  Compile-time options:
    DEBUGGING
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_USE_DEVEL
    USE_64_BIT_ALL
    USE_64_BIT_INT
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
  Built under linux
  Compiled at Feb 10 2021 09:50:07
  %ENV:
    PERLBREW_BASHRC_VERSION="0.43"
    PERLBREW_HOME="/home/tony/.perlbrew"
    PERLBREW_MANPATH=""
    PERLBREW_PATH="/home/tony/perl5/perlbrew/bin"
    PERLBREW_ROOT="/home/tony/perl5/perlbrew"
    PERLBREW_VERSION="0.67"
  @INC:
    lib
    /usr/local/lib/perl5/site_perl/5.33.7/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.33.7
    /usr/local/lib/perl5/5.33.7/x86_64-linux
    /usr/local/lib/perl5/5.33.7

[tonycoz]

There's still some misbehaviour even with #18552:

tony@venus:.../git/perl4$ ./perl -Ilib -Mfeature=try -le 'my @x = 0; sub foo :lvalue { print "Hello\n"; return @x} (foo()) = (1, 2); print @x'
Hello

12
tony@venus:.../git/perl4$ ./perl -Ilib -Mfeature=try -le 'my @x = 0; sub foo :lvalue { try { print "Hello\n"; return @x } catch ($e) {}} (foo()) = (1, 2); print @x'
try/catch is experimental at -e line 1.
try/catch is experimental at -e line 1.
Hello

1

[leonerd]

Having now merged your commit (3ab1cbe) in, I now get a consistent output:

$ ./perl -Ilib -Mfeature=try -le 'my @x = 0; sub foo :lvalue { try { print "Hello\n"; return @x } catch ($e) {}} (foo()) = (1, 2); print @x'
try/catch is experimental at -e line 1.
try/catch is experimental at -e line 1.
Hello

12

[leonerd]

A unit test for this case is now added in #18552

[xenu]

According to the comments in this ticket, the issue is resolved.