RC_STACK asserts without DEBUG_LEAKING_SCALARS

An earlier commit added some asserts to the old-style and new-style
stack push/pop functions such as PUSHs() or rpp_popfree_1().  These
assert that the stack is reference-counted or not as appropriate.

These asserts were enabled only if perl was built with all of

    DEBUGGING && PERL_RC_STACK && DEBUG_LEAKING_SCALARS.

This commit makes the asserts available under just

    DEBUGGING && PERL_RC_STACK

Initially  I was worried about the performance implications (you expect
DEBUGGING builds to be slow, but not *too* slow), but they don't seem
too bad. So by making them more likely to be enabled, they're more
likely to help people spot code that needs fixing (e.g. code still doing
POPs when the stack is reference counted and the function hasn't been
wrapped).

Author: iabyn

inline.h

@@ -439,9 +439,7 @@ Perl_rpp_popfree_to(pTHX_ SV **sp)
 
     assert(sp <= PL_stack_sp);
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     while (PL_stack_sp > sp) {
         SV *sv = *PL_stack_sp--;
         SvREFCNT_dec(sv);
@@ -466,9 +464,7 @@ Perl_rpp_popfree_1(pTHX)
     PERL_ARGS_ASSERT_RPP_POPFREE_1;
 
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     SV *sv = *PL_stack_sp--;
     SvREFCNT_dec(sv);
 #else
@@ -493,9 +489,7 @@ Perl_rpp_popfree_2(pTHX)
     PERL_ARGS_ASSERT_RPP_POPFREE_2;
 
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     for (int i = 0; i < 2; i++) {
         SV *sv = *PL_stack_sp--;
         SvREFCNT_dec(sv);
@@ -534,9 +528,7 @@ Perl_rpp_pop_1_norc(pTHX)
 #ifndef PERL_RC_STACK
     SvREFCNT_inc(sv);
 #else
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
 #endif
     return sv;
 }
@@ -563,9 +555,7 @@ Perl_rpp_push_1(pTHX_ SV *sv)
 
     *++PL_stack_sp = sv;
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     SvREFCNT_inc_simple_void_NN(sv);
 #endif
 }
@@ -578,9 +568,7 @@ Perl_rpp_push_2(pTHX_ SV *sv1, SV *sv2)
     *++PL_stack_sp = sv1;
     *++PL_stack_sp = sv2;
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     SvREFCNT_inc_simple_void_NN(sv1);
     SvREFCNT_inc_simple_void_NN(sv2);
 #endif
@@ -624,9 +612,7 @@ Perl_rpp_push_1_norc(pTHX_ SV *sv)
 
     *++PL_stack_sp = sv;
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
 #else
     sv_2mortal(sv);
 #endif
@@ -649,9 +635,7 @@ Perl_rpp_replace_1_1(pTHX_ SV *sv)
     PERL_ARGS_ASSERT_RPP_REPLACE_1_1;
 
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     SV *oldsv = *PL_stack_sp;
     *PL_stack_sp = sv;
     SvREFCNT_inc_simple_void_NN(sv);
@@ -678,9 +662,7 @@ Perl_rpp_replace_2_1(pTHX_ SV *sv)
     PERL_ARGS_ASSERT_RPP_REPLACE_2_1;
 
 #ifdef PERL_RC_STACK
-#  ifdef DEBUG_LEAKING_SCALARS
     assert(rpp_stack_is_rc());
-#  endif
     /* replace PL_stack_sp[-1] first; leave PL_stack_sp[0] in place while
      * we free [-1], so if an exception occurs, [0] will still be freed.
      */
@@ -767,14 +749,14 @@ context.
 PERL_STATIC_INLINE bool
 Perl_rpp_is_lone(pTHX_ SV *sv)
 {
-#if defined(PERL_RC_STACK) && defined(DEBUG_LEAKING_SCALARS)
+#ifdef PERL_RC_STACK
     /* note that rpp_is_lone() can be used in wrapped pp functions,
      * where technically the stack is no longer ref-counted; but because
      * the args are non-RC copies of RC args further down the stack, we
      * can't be in a *completely* non-ref stack.
      */
     assert(AvREAL(PL_curstack));
-#  endif
+#endif
 
     return SvREFCNT(sv) <= cBOOL(SvTEMP(sv))
 #ifdef PERL_RC_STACK

pod/perlguts.pod

@@ -4477,8 +4477,7 @@ API.
 A reference-counted perl can be built using the PERL_RC_STACK define.
 For development and debugging purposes, it is best to enable leaking
 scalar debugging too, as that displays extra information about scalars
-that have leaked or been prematurely freed, and it also enables extra
-assertions in the macros and functions which manipulate the stack:
+that have leaked or been prematurely freed.
 
     Configure -DDEBUGGING \
       -Accflags='-DPERL_RC_STACK -DDEBUG_LEAKING_SCALARS'
@@ -4896,9 +4895,9 @@ call_sv() is called from a standard PP function (rpp_stack_is_rc() is
 true) or from a wrapped PP or XS function (rpp_stack_is_rc() is false).
 Note that you're unlikely to need to use this function, as in most places,
 such as PP or XS functions, it is always RC or non-RC respectively. In
-fact, under C<DEBUG_LEAKING_SCALARS>, PUSHs() and similar macros include
-an C<assert(!rpp_stack_is_rc())>, while rpp_push_1() and similar functions
-have C<assert(rpp_stack_is_rc())>.
+fact on debugging builds under C<PERL_RC_STACK>, PUSHs() and similar
+macros include an C<assert(!rpp_stack_is_rc())>, while rpp_push_1() and
+similar functions have C<assert(rpp_stack_is_rc())>.
 
 The macros for pushing new stackinfos have been replaced with inline
 functions which don't rely on C<dSP> being in scope, and which have less

pp.h

@@ -210,7 +210,7 @@ Pops an unsigned long off the stack.
 #define RETURNOP(o)	return (PUTBACK, o)
 #define RETURNX(x)	return (x, PUTBACK, NORMAL)
 
-#if defined(PERL_RC_STACK) && defined(DEBUG_LEAKING_SCALARS)
+#ifdef PERL_RC_STACK
 #  define POPs		(assert(!rpp_stack_is_rc()), *sp--)
 #else
 #  define POPs		(*sp--)
@@ -543,7 +543,7 @@ Does not use C<TARG>.  See also C<L</XPUSHu>>, C<L</mPUSHu>> and C<L</PUSHu>>.
             sv_setnv_mg(targ, TARGn_nv);                                \
     } STMT_END
 
-#if defined(PERL_RC_STACK) && defined(DEBUG_LEAKING_SCALARS)
+#ifdef PERL_RC_STACK
 #  define PUSHs(s)	(assert(!rpp_stack_is_rc()), *++sp = (s))
 #else
 #  define PUSHs(s)	(*++sp = (s))