Fix qx, `` and <<`` overrides

This resolves two RT tickets:
• #115330 is that qx and `` overrides do not support interpolation.
• #119827 is that <<`` does not support readpipe overrides at all.

The obvious fix for #115330 fixes #119827 at the same time.

When quote-like operators are parsed, after the string has been
scanned S_sublex_push is called, which decides which of two paths
to follow:
1) For things not requiring interpolation, the string is passed to
   tokeq (originally called q, it handles double backslashes and back-
   slashed delimiters) and returned to the parser immediately.
2) For anything that interpolates, the lexer enters a special inter-
   polation mode (LEX_INTERPPUSH) and goes through a more complex
   sequence over the next few calls (e.g., qq"a.$b.c" is turned into
  ‘stringify ( "a." . $ b . ".c" )’).

When commit e3f73d4ed (Oct 2006, perl 5.10) added support for overrid-
ing `` and qx with a readpipe sub, it did so by creating an entersub
op in toke.c and making S_sublex_push follow path no. 1, taking the
result if tokeq and inserting it into the already-constructed op tree
for the sub call.

That approach caused interpolation to be skipped when qx or `` is
overridden.  Furthermore it didn’t touch <<`` at all.

The easiest solution is to let toke.c follow its normal path and
create a backtick op (instead of trying to half-intercept it), and
to deal with override lookup afterwards in ck_backtick, the same way
require overrides are handled.  Since <<`` also turns into a backtick
op, it gets handled too that way.

1 files changed, 2 insertions, 31 deletions

diff --git a/toke.c b/toke.c
index b42929e422..66447e3677 100644
--- a/toke.c
+++ b/toke.c
@@ -2606,14 +2606,6 @@ S_sublex_start(pTHX)
 	    PL_expect = XTERMORDORDOR;
 	return THING;
     }
-    else if (op_type == OP_BACKTICK && PL_lex_op) {
-	/* readpipe() was overridden */
-	cSVOPx(cLISTOPx(cUNOPx(PL_lex_op)->op_first)->op_first->op_sibling)->op_sv = tokeq(PL_lex_stuff);
-	pl_yylval.opval = PL_lex_op;
-	PL_lex_op = NULL;
-	PL_lex_stuff = NULL;
-	return THING;
-    }
 
     PL_sublex_info.super_state = PL_lex_state;
     PL_sublex_info.sub_inwhat = (U16)op_type;
@@ -4472,27 +4464,6 @@ S_find_in_my_stash(pTHX_ const char *pkgname, STRLEN len)
     return gv_stashpvn(pkgname, len, UTF ? SVf_UTF8 : 0);
 }
 
-/*
- * S_readpipe_override
- * Check whether readpipe() is overridden, and generates the appropriate
- * optree, provided sublex_start() is called afterwards.
- */
-STATIC void
-S_readpipe_override(pTHX)
-{
-    GV **gvp;
-    GV *gv_readpipe = gv_fetchpvs("readpipe", GV_NOTQUAL, SVt_PVCV);
-    pl_yylval.ival = OP_BACKTICK;
-    if ((gv_readpipe = gv_override("readpipe",8)))
-    {
-	COPLINE_SET_FROM_MULTI_END;
-	PL_lex_op = (OP*)newUNOP(OP_ENTERSUB, OPf_STACKED,
-	    op_append_elem(OP_LIST,
-		newSVOP(OP_CONST, 0, &PL_sv_undef), /* value will be read later */
-		newCVREF(0, newGVOP(OP_GV, 0, gv_readpipe))));
-    }
-}
-
 #ifdef PERL_MAD 
  /*
  * Perl_madlex
@@ -6933,7 +6904,7 @@ Perl_yylex(pTHX)
 	    no_op("Backticks",s);
 	if (!s)
 	    missingterm(NULL);
-	readpipe_override();
+	pl_yylval.ival = OP_BACKTICK;
 	TERM(sublex_start());
 
     case '\\':
@@ -8489,7 +8460,7 @@ Perl_yylex(pTHX)
 	    s = scan_str(s,!!PL_madskills,FALSE,FALSE, FALSE);
 	    if (!s)
 		missingterm(NULL);
-	    readpipe_override();
+	    pl_yylval.ival = OP_BACKTICK;
 	    TERM(sublex_start());
 
 	case KEY_return: