Turn $$ into a magical readonly variable that always fetches getpid() instead of caching it

The intent is that by not caching $$, we eliminate one opportunity for bugs:
If one embeds Perl or uses XS and calls fork(3) from C, Perls notion of $$
may go out of sync with what getpid() returns. By always fetching the
value of $$ via getpid(), this bug opportunity is eliminated. The overhead
of always fetching $$ should be small and is likely only used for tempfile
creation, which should be dwarfed by file system accesses.

1 files changed, 0 insertions, 6 deletions

diff --git a/pp_sys.c b/pp_sys.c
index 186465f30d..aa74cef58e 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -4017,12 +4017,6 @@ PP(pp_fork)
     if (childpid < 0)
 	RETSETUNDEF;
     if (!childpid) {
-	GV * const tmpgv = gv_fetchpvs("$", GV_ADD|GV_NOTQUAL, SVt_PV);
-	if (tmpgv) {
-            SvREADONLY_off(GvSV(tmpgv));
-	    sv_setiv(GvSV(tmpgv), (IV)PerlProc_getpid());
-            SvREADONLY_on(GvSV(tmpgv));
-        }
 #ifdef THREADS_HAVE_PIDS
 	PL_ppid = (IV)getppid();
 #endif