From e3331d8cb3b0e99a2fd5ef003bc9f7363aceb84a Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Sun, 18 Aug 2019 16:11:11 +0900
Subject: [PATCH] Initialize excess array elements with zero

---
 parse.c | 35 +++++++++++++++++++++++++++++------
 tests   |  8 ++++++++
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/parse.c b/parse.c
index 0699f9f..8f83690 100644
--- a/parse.c
+++ b/parse.c
@@ -700,8 +700,21 @@ static Node *new_desg_node(Var *var, Designator *desg, Node *rhs) {
   return new_unary(ND_EXPR_STMT, node, rhs->tok);
 }
 
+static Node *lvar_init_zero(Node *cur, Var *var, Type *ty, Designator *desg) {
+  if (ty->kind == TY_ARRAY) {
+    for (int i = 0; i < ty->array_len; i++) {
+      Designator desg2 = {desg, i++};
+      cur = lvar_init_zero(cur, var, ty->base, &desg2);
+    }
+    return cur;
+  }
+
+  cur->next = new_desg_node(var, desg, new_num(0, token));
+  return cur->next;
+}
+
 // lvar-initializer2 = assign
-//                   | "{" lvar-initializer2 ("," lvar-initializer2)* ","? "}"
+//                   | "{" (lvar-initializer2 ("," lvar-initializer2)* ","?)? "}"
 //
 // An initializer for a local variable is expanded to multiple
 // assignments. For example, this function creates the following
@@ -713,17 +726,27 @@ static Node *new_desg_node(Var *var, Designator *desg, Node *rhs) {
 //   x[1][0]=4;
 //   x[1][1]=5;
 //   x[1][2]=6;
+//
+// If an initializer list is shorter than an array, excess array
+// elements are initialized with 0.
 static Node *lvar_initializer2(Node *cur, Var *var, Type *ty, Designator *desg) {
   if (ty->kind == TY_ARRAY) {
     expect("{");
     int i = 0;
 
-    do {
-      Designator desg2 = {desg, i++};
-      cur = lvar_initializer2(cur, var, ty->base, &desg2);
-    } while (!peek_end() && consume(","));
-
+    if (!peek("}")) {
+      do {
+        Designator desg2 = {desg, i++};
+        cur = lvar_initializer2(cur, var, ty->base, &desg2);
+      } while (!peek_end() && consume(","));
+    }
     expect_end();
+
+    // Set excess array elements to zero.
+    while (i < ty->array_len) {
+      Designator desg2 = {desg, i++};
+      cur = lvar_init_zero(cur, var, ty->base, &desg2);
+    }
     return cur;
   }
 
diff --git a/tests b/tests
index 748803b..1bdd9aa 100644
--- a/tests
+++ b/tests
@@ -482,10 +482,18 @@ int main() {
   assert(3, ({ int x[3]={1,2,3}; x[2]; }), "int x[3]={1,2,3}; x[0];");
   assert(3, ({ int x[3]={1,2,3,}; x[2]; }), "int x[3]={1,2,3}; x[0];");
 
+  assert(0, ({ int x[3]={}; x[0]; }), "int x[3]={}; x[0];");
+  assert(0, ({ int x[3]={}; x[1]; }), "int x[3]={}; x[1];");
+  assert(0, ({ int x[3]={}; x[2]; }), "int x[3]={}; x[2];");
+
   assert(2, ({ int x[2][3]={{1,2,3},{4,5,6}}; x[0][1]; }), "int x[2][3]={{1,2,3},{4,5,6}}; x[0][1];");
   assert(4, ({ int x[2][3]={{1,2,3},{4,5,6}}; x[1][0]; }), "int x[2][3]={{1,2,3},{4,5,6}}; x[1][0];");
   assert(6, ({ int x[2][3]={{1,2,3},{4,5,6}}; x[1][2]; }), "int x[2][3]={{1,2,3},{4,5,6}}; x[1][2];");
 
+  assert(2, ({ int x[2][3]={{1,2}}; x[0][1]; }), "int x[2][3]={{1,2}}; x[0][1];");
+  assert(0, ({ int x[2][3]={{1,2}}; x[1][0]; }), "int x[2][3]={{1,2}}; x[1][0];");
+  assert(0, ({ int x[2][3]={{1,2}}; x[1][2]; }), "int x[2][3]={{1,2}}; x[1][2];");
+
   printf("OK\n");
   return 0;
 }
-- 
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