[perl #119797] Fix if/else in lvalue sub

When if/else/unless is the last thing in an lvalue sub, the lvalue
context is not always propagated properly and scope exit tries to
copy things, including arrays, resulting in ‘Bizarre copy of ARRAY’.

This commit fixes the bizarre copy by flagging any leave op that is
part of an lvalue sub’s return sequence, using the OPpLEAVE flag added
for this purpose in the previous commit.  Then pp_leave uses that flag
to avoid copying return values, but protects them via the mortals
stack just like pp_leavesublv (actually pp_ctl.c:S_return_lvalues).

For ‘if’ and ‘unless’ without ‘else’, the lvalue context was not being
propagated, resulting in arrays’ getting flattened despite the lvalue
context.  op_lvalue_flags in op.c needed to handle AND and OR ops,
which ‘if’ and ‘unless’ compile to, to make this work.

1 files changed, 23 insertions, 9 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index ded6c9038f..4be2b194f9 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -2033,8 +2033,13 @@ PP(pp_dbstate)
 	return NORMAL;
 }
 
+/* SVs on the stack that have any of the flags passed in are left as is.
+   Other SVs are protected via the mortals stack if lvalue is true, and
+   copied otherwise. */
+
 STATIC SV **
-S_adjust_stack_on_leave(pTHX_ SV **newsp, SV **sp, SV **mark, I32 gimme, U32 flags)
+S_adjust_stack_on_leave(pTHX_ SV **newsp, SV **sp, SV **mark, I32 gimme,
+			      U32 flags, bool lvalue)
 {
     bool padtmp = 0;
     PERL_ARGS_ASSERT_ADJUST_STACK_ON_LEAVE;
@@ -2046,7 +2051,10 @@ S_adjust_stack_on_leave(pTHX_ SV **newsp, SV **sp, SV **mark, I32 gimme, U32 fla
     if (gimme == G_SCALAR) {
 	if (MARK < SP)
 	    *++newsp = ((SvFLAGS(*SP) & flags) || (padtmp && SvPADTMP(*SP)))
-			    ? *SP : sv_mortalcopy(*SP);
+			    ? *SP
+			    : lvalue
+				? sv_2mortal(SvREFCNT_inc_simple_NN(*SP))
+				: sv_mortalcopy(*SP);
 	else {
 	    /* MEXTEND() only updates MARK, so reuse it instead of newsp. */
 	    MARK = newsp;
@@ -2061,7 +2069,9 @@ S_adjust_stack_on_leave(pTHX_ SV **newsp, SV **sp, SV **mark, I32 gimme, U32 fla
 	    if ((SvFLAGS(*MARK) & flags) || (padtmp && SvPADTMP(*MARK)))
 		*++newsp = *MARK;
 	    else {
-		*++newsp = sv_mortalcopy(*MARK);
+		*++newsp = lvalue
+			    ? sv_2mortal(SvREFCNT_inc_simple_NN(*MARK))
+			    : sv_mortalcopy(*MARK);
 		TAINT_NOT;	/* Each item is independent */
 	    }
 	}
@@ -2104,7 +2114,8 @@ PP(pp_leave)
     gimme = OP_GIMME(PL_op, (cxstack_ix >= 0) ? gimme : G_SCALAR);
 
     TAINT_NOT;
-    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme, SVs_PADTMP|SVs_TEMP);
+    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme, SVs_PADTMP|SVs_TEMP,
+			       PL_op->op_private & OPpLVALUE);
     PL_curpm = newpm;	/* Don't pop $1 et al till now */
 
     LEAVE_with_name("block");
@@ -2266,7 +2277,7 @@ PP(pp_leaveloop)
     newsp = PL_stack_base + cx->blk_loop.resetsp;
 
     TAINT_NOT;
-    SP = adjust_stack_on_leave(newsp, SP, MARK, gimme, 0);
+    SP = adjust_stack_on_leave(newsp, SP, MARK, gimme, 0, FALSE);
     PUTBACK;
 
     POPLOOP(cx);	/* Stack values are safe: release loop vars ... */
@@ -4315,7 +4326,7 @@ PP(pp_leaveeval)
 
     TAINT_NOT;
     SP = adjust_stack_on_leave((gimme == G_VOID) ? SP : newsp, SP, newsp,
-				gimme, SVs_TEMP);
+				gimme, SVs_TEMP, FALSE);
     PL_curpm = newpm;	/* Don't pop $1 et al till now */
 
 #ifdef DEBUGGING
@@ -4413,7 +4424,8 @@ PP(pp_leavetry)
     PERL_UNUSED_VAR(optype);
 
     TAINT_NOT;
-    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme, SVs_PADTMP|SVs_TEMP);
+    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme,
+			       SVs_PADTMP|SVs_TEMP, FALSE);
     PL_curpm = newpm;	/* Don't pop $1 et al till now */
 
     LEAVE_with_name("eval_scope");
@@ -4459,7 +4471,8 @@ PP(pp_leavegiven)
     assert(CxTYPE(cx) == CXt_GIVEN);
 
     TAINT_NOT;
-    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme, SVs_PADTMP|SVs_TEMP);
+    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme,
+			       SVs_PADTMP|SVs_TEMP, FALSE);
     PL_curpm = newpm;	/* Don't pop $1 et al till now */
 
     LEAVE_with_name("given");
@@ -5037,7 +5050,8 @@ PP(pp_leavewhen)
     assert(CxTYPE(cx) == CXt_WHEN);
 
     TAINT_NOT;
-    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme, SVs_PADTMP|SVs_TEMP);
+    SP = adjust_stack_on_leave(newsp, SP, newsp, gimme,
+			       SVs_PADTMP|SVs_TEMP, FALSE);
     PL_curpm = newpm;   /* pop $1 et al */
 
     LEAVE_with_name("when");