Fix CORE::glob

This commit makes CORE::glob bypassing glob overrides.

A side effect of the fix is that, with the default glob implementa-
tion, undefining *CORE::GLOBAL::glob no longer results in an ‘unde-
fined subroutine’ error.

Another side effect is that compilation of a glob op no longer assumes
that the loading of File::Glob will create the *CORE::GLOB::glob type-
glob.  ‘++$INC{"File/Glob.pm"}; sub File::Glob::csh_glob; eval '<*>';’
used to crash.

This is accomplished using a mechanism similar to lock() and
threads::shared.  There is a new PL_globhook interpreter varia-
ble that pp_glob calls when there is no override present.  Thus,
File::Glob (which is supposed to be transparent, as it *is* the
built-in implementation) no longer interferes with the user mechanism
for overriding glob.

This removes one tier from the five or so hacks that constitute glob’s
implementation, and which work together to make it one of the buggiest
and most inconsistent areas of Perl.

1 files changed, 9 insertions, 10 deletions

diff --git a/op.c b/op.c
index 7690e4c59b..c34dec5f1c 100644
--- a/op.c
+++ b/op.c
@@ -3091,6 +3091,7 @@ OP *
 Perl_convert(pTHX_ I32 type, I32 flags, OP *o)
 {
     dVAR;
+    if (type < 0) type = -type, flags |= OPf_SPECIAL;
     if (!o || o->op_type != OP_LIST)
 	o = newLISTOP(OP_LIST, 0, o, NULL);
     else
@@ -7988,6 +7989,7 @@ Perl_ck_glob(pTHX_ OP *o)
 {
     dVAR;
     GV *gv;
+    const bool core = o->op_flags & OPf_SPECIAL;
 
     PERL_ARGS_ASSERT_CK_GLOB;
 
@@ -7995,7 +7997,8 @@ Perl_ck_glob(pTHX_ OP *o)
     if ((o->op_flags & OPf_KIDS) && !cLISTOPo->op_first->op_sibling)
 	op_append_elem(OP_GLOB, o, newDEFSVOP()); /* glob() => glob($_) */
 
-    if (!((gv = gv_fetchpvs("glob", GV_NOTQUAL, SVt_PVCV))
+    if (core) gv = NULL;
+    else if (!((gv = gv_fetchpvs("glob", GV_NOTQUAL, SVt_PVCV))
 	  && GvCVu(gv) && GvIMPORTED_CV(gv)))
     {
 	gv = gv_fetchpvs("CORE::GLOBAL::glob", 0, SVt_PVCV);
@@ -8003,21 +8006,13 @@ Perl_ck_glob(pTHX_ OP *o)
 
 #if !defined(PERL_EXTERNAL_GLOB)
     if (!(gv && GvCVu(gv) && GvIMPORTED_CV(gv))) {
-	GV *glob_gv;
 	ENTER;
 	Perl_load_module(aTHX_ PERL_LOADMOD_NOIMPORT,
 		newSVpvs("File::Glob"), NULL, NULL, NULL);
-	if((glob_gv = gv_fetchpvs("File::Glob::csh_glob", 0, SVt_PVCV))) {
-	    gv = gv_fetchpvs("CORE::GLOBAL::glob", 0, SVt_PVCV);
-	    GvCV_set(gv, GvCV(glob_gv));
-	    SvREFCNT_inc_void(MUTABLE_SV(GvCV(gv)));
-	    GvIMPORTED_CV_on(gv);
-	}
 	LEAVE;
     }
-#endif /* PERL_EXTERNAL_GLOB */
+#endif /* !PERL_EXTERNAL_GLOB */
 
-    assert(!(o->op_flags & OPf_SPECIAL));
     if (gv && GvCVu(gv) && GvIMPORTED_CV(gv)) {
 	/* convert
 	 *     glob
@@ -8044,8 +8039,12 @@ Perl_ck_glob(pTHX_ OP *o)
 	o->op_targ = OP_GLOB; /* hint at what it used to be: eg in newWHILEOP */
 	return o;
     }
+    else o->op_flags &= ~OPf_SPECIAL;
     gv = newGVgen("main");
     gv_IOadd(gv);
+#ifndef PERL_EXTERNAL_GLOB
+    sv_setiv(GvSVn(gv),PL_glob_index++);
+#endif
     op_append_elem(OP_GLOB, o, newGVOP(OP_GV, 0, gv));
     scalarkids(o);
     return o;