Don’t allow OPpTARGET_MY on postdec/inc

I was wrong in 9e319cc4f.  postfix ++/-- writes to its return value
before reading its argument.  If we optimise away the scalar
assignment in

    $a = $b++;

(that’s what OPpTARGET_MY does), then $a gets written to before $b is
read.  If $a and $b are the same, we get the wrong answer.  This bug
has been present under ‘use integer’ since 5.6.0.  I accidentally
extended it to non-integer ++/-- in 9e319cc4f.

(It’s not likely that someone will write $a = $b++, but it could hap-
pen inadvertently in more complex code.)

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/B/Op_private.pm b/lib/B/Op_private.pm
index 730964c261..cdc91dc510 100644
--- a/lib/B/Op_private.pm
+++ b/lib/B/Op_private.pm
@@ -142,7 +142,7 @@ $bits{$_}{7} = 'OPpPV_IS_UTF8' for qw(dump goto last next redo);
 $bits{$_}{6} = 'OPpREFCOUNTED' for qw(leave leaveeval leavesub leavesublv leavewrite);
 $bits{$_}{6} = 'OPpRUNTIME' for qw(match pushre qr subst substcont);
 $bits{$_}{2} = 'OPpSLICEWARNING' for qw(aslice hslice padav padhv rv2av rv2hv);
-$bits{$_}{4} = 'OPpTARGET_MY' for qw(abs add atan2 chdir chmod chomp chown chr chroot concat cos crypt divide exec exp flock getpgrp getppid getpriority hex i_add i_divide i_modulo i_multiply i_negate i_postdec i_postinc i_subtract index int kill left_shift length link log match mkdir modulo multiply oct ord postdec postinc pow push rand rename repeat right_shift rindex rmdir schomp setpgrp setpriority sin sleep split sqrt srand stringify subst subtract symlink system time trans transr unlink unshift utime vec wait waitpid);
+$bits{$_}{4} = 'OPpTARGET_MY' for qw(abs add atan2 chdir chmod chomp chown chr chroot concat cos crypt divide exec exp flock getpgrp getppid getpriority hex i_add i_divide i_modulo i_multiply i_negate i_subtract index int kill left_shift length link log match mkdir modulo multiply oct ord pow push rand rename repeat right_shift rindex rmdir schomp setpgrp setpriority sin sleep split sqrt srand stringify subst subtract symlink system time trans transr unlink unshift utime vec wait waitpid);
 $bits{$_}{5} = 'OPpTRANS_COMPLEMENT' for qw(trans transr);
 $bits{$_}{7} = 'OPpTRANS_DELETE' for qw(trans transr);
 $bits{$_}{0} = 'OPpTRANS_FROM_UTF' for qw(trans transr);