[Bug #22002] Never pop when compiling branch predicate

The value is always needed. Now prism emits the same instructions as parse.y for the added test case.

`defined?`/`flip-flop` caused `argument stack underflow`, `and`/`or` segfaulted during runtime.

Author: Earlopain

prism_compile.c

@@ -964,10 +964,10 @@ pm_code_location(pm_scope_node_t *scope_node, const pm_node_t *node)
 
 static void
 pm_compile_branch_condition(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const pm_node_t *cond,
-                         LABEL *then_label, LABEL *else_label, bool popped, pm_scope_node_t *scope_node);
+                         LABEL *then_label, LABEL *else_label, pm_scope_node_t *scope_node);
 
 static void
-pm_compile_logical(rb_iseq_t *iseq, LINK_ANCHOR *const ret, pm_node_t *cond, LABEL *then_label, LABEL *else_label, bool popped, pm_scope_node_t *scope_node)
+pm_compile_logical(rb_iseq_t *iseq, LINK_ANCHOR *const ret, pm_node_t *cond, LABEL *then_label, LABEL *else_label, pm_scope_node_t *scope_node)
 {
     const pm_node_location_t location = PM_NODE_START_LOCATION(cond);
 
@@ -977,17 +977,14 @@ pm_compile_logical(rb_iseq_t *iseq, LINK_ANCHOR *const ret, pm_node_t *cond, LAB
     if (!then_label) then_label = label;
     else if (!else_label) else_label = label;
 
-    pm_compile_branch_condition(iseq, seq, cond, then_label, else_label, popped, scope_node);
+    pm_compile_branch_condition(iseq, seq, cond, then_label, else_label, scope_node);
 
     if (LIST_INSN_SIZE_ONE(seq)) {
         INSN *insn = (INSN *) ELEM_FIRST_INSN(FIRST_ELEMENT(seq));
         if (insn->insn_id == BIN(jump) && (LABEL *)(insn->operands[0]) == label) return;
     }
 
-    if (!label->refcnt) {
-        if (popped) PUSH_INSN(ret, location, putnil);
-    }
-    else {
+    if (label->refcnt) {
         PUSH_LABEL(seq, label);
     }
 
@@ -1059,22 +1056,22 @@ pm_compile_flip_flop(const pm_flip_flop_node_t *flip_flop_node, LABEL *else_labe
 static void pm_compile_defined_expr(rb_iseq_t *iseq, const pm_node_t *node, const pm_node_location_t *node_location, LINK_ANCHOR *const ret, bool popped, pm_scope_node_t *scope_node, bool in_condition);
 
 static void
-pm_compile_branch_condition(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const pm_node_t *cond, LABEL *then_label, LABEL *else_label, bool popped, pm_scope_node_t *scope_node)
+pm_compile_branch_condition(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const pm_node_t *cond, LABEL *then_label, LABEL *else_label, pm_scope_node_t *scope_node)
 {
     const pm_node_location_t location = PM_NODE_START_LOCATION(cond);
 
 again:
     switch (PM_NODE_TYPE(cond)) {
       case PM_AND_NODE: {
         const pm_and_node_t *cast = (const pm_and_node_t *) cond;
-        pm_compile_logical(iseq, ret, cast->left, NULL, else_label, popped, scope_node);
+        pm_compile_logical(iseq, ret, cast->left, NULL, else_label, scope_node);
 
         cond = cast->right;
         goto again;
       }
       case PM_OR_NODE: {
         const pm_or_node_t *cast = (const pm_or_node_t *) cond;
-        pm_compile_logical(iseq, ret, cast->left, then_label, NULL, popped, scope_node);
+        pm_compile_logical(iseq, ret, cast->left, then_label, NULL, scope_node);
 
         cond = cast->right;
         goto again;
@@ -1095,11 +1092,11 @@ pm_compile_branch_condition(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const pm_no
         PUSH_INSNL(ret, location, jump, then_label);
         return;
       case PM_FLIP_FLOP_NODE:
-        pm_compile_flip_flop((const pm_flip_flop_node_t *) cond, else_label, then_label, iseq, location.line, ret, popped, scope_node);
+        pm_compile_flip_flop((const pm_flip_flop_node_t *) cond, else_label, then_label, iseq, location.line, ret, false, scope_node);
         return;
       case PM_DEFINED_NODE: {
         const pm_defined_node_t *cast = (const pm_defined_node_t *) cond;
-        pm_compile_defined_expr(iseq, cast->value, &location, ret, popped, scope_node, true);
+        pm_compile_defined_expr(iseq, cast->value, &location, ret, false, scope_node, true);
         break;
       }
       default: {
@@ -1143,7 +1140,7 @@ pm_compile_conditional(rb_iseq_t *iseq, const pm_node_location_t *node_location,
     LABEL *end_label = NULL;
 
     DECL_ANCHOR(cond_seq);
-    pm_compile_branch_condition(iseq, cond_seq, predicate, then_label, else_label, false, scope_node);
+    pm_compile_branch_condition(iseq, cond_seq, predicate, then_label, else_label, scope_node);
     PUSH_SEQ(ret, cond_seq);
 
     rb_code_location_t conditional_location = { 0 };
@@ -1291,10 +1288,10 @@ pm_compile_loop(rb_iseq_t *iseq, const pm_node_location_t *node_location, pm_nod
     PUSH_LABEL(ret, next_label);
 
     if (type == PM_WHILE_NODE) {
-        pm_compile_branch_condition(iseq, ret, predicate, redo_label, end_label, popped, scope_node);
+        pm_compile_branch_condition(iseq, ret, predicate, redo_label, end_label, scope_node);
     }
     else if (type == PM_UNTIL_NODE) {
-        pm_compile_branch_condition(iseq, ret, predicate, end_label, redo_label, popped, scope_node);
+        pm_compile_branch_condition(iseq, ret, predicate, end_label, redo_label, scope_node);
     }
 
     PUSH_LABEL(ret, end_label);
@@ -7693,7 +7690,7 @@ pm_compile_case_node(rb_iseq_t *iseq, const pm_case_node_t *cast, const pm_node_
                 }
                 else {
                     LABEL *next_label = NEW_LABEL(pm_node_line_number_cached(condition, scope_node));
-                    pm_compile_branch_condition(iseq, cond_seq, condition, label, next_label, false, scope_node);
+                    pm_compile_branch_condition(iseq, cond_seq, condition, label, next_label, scope_node);
                     PUSH_LABEL(cond_seq, next_label);
                 }
             }

test/ruby/test_syntax.rb

@@ -1911,6 +1911,24 @@ def test_classdef_in_cond
     assert_valid_syntax('while class Foo a = tap do end; end; break; end')
   end
 
+  def test_while_until_conditional_bug_22002
+    @foo = 123 until defined?(@foo)
+    assert_equal(123, @foo)
+
+    @bar = 456 while @bar==nil..true
+    assert_equal(456, @bar)
+
+    while false and @baz
+      @baz = 789
+    end
+    assert_equal(nil, @baz)
+
+    until true || @baz
+      @baz = 789
+    end
+    assert_equal(nil, @baz)
+  end
+
   def test_command_with_cmd_brace_block
     assert_valid_syntax('obj.foo (1) {}')
     assert_valid_syntax('obj::foo (1) {}')