Handle struct initializers for local variables

parse.c

@@ -682,7 +682,8 @@ static void global_var(void) {
 typedef struct Designator Designator;
 struct Designator {
   Designator *next;
-  int idx;
+  int idx;     // array
+  Member *mem; // struct
 };
 
 // Creates a node for an array access. For example, if var represents
@@ -693,6 +694,13 @@ static Node *new_desg_node2(Var *var, Designator *desg, Token *tok) {
     return new_var_node(var, tok);
 
   Node *node = new_desg_node2(var, desg->next, tok);
+
+  if (desg->mem) {
+    node = new_unary(ND_MEMBER, node, desg->mem->tok);
+    node->member = desg->mem;
+    return node;
+  }
+
   node = new_add(node, new_num(desg->idx, tok), tok);
   return new_unary(ND_DEREF, node, tok);
 }
@@ -730,6 +738,9 @@ static Node *lvar_init_zero(Node *cur, Var *var, Type *ty, Designator *desg) {
 //   x[1][1]=5;
 //   x[1][2]=6;
 //
+// Struct members are initialized in declaration order. For example,
+// `struct { int a; int b; } x = {1, 2}` sets x.a to 1 and x.b to 2.
+//
 // There are a few special rules for ambiguous initializers and
 // shorthand notations:
 //
@@ -799,6 +810,27 @@ static Node *lvar_initializer2(Node *cur, Var *var, Type *ty, Designator *desg)
     return cur;
   }
 
+  if (ty->kind == TY_STRUCT) {
+    expect("{");
+    Member *mem = ty->members;
+
+    if (!peek("}")) {
+      do {
+        Designator desg2 = {desg, 0, mem};
+        cur = lvar_initializer2(cur, var, mem->ty, &desg2);
+        mem = mem->next;
+      } while (!peek_end() && consume(","));
+    }
+    expect_end();
+
+    // Set excess struct elements to zero.
+    for (; mem; mem = mem->next) {
+      Designator desg2 = {desg, 0, mem};
+      cur = lvar_init_zero(cur, var, mem->ty, &desg2);
+    }
+    return cur;
+  }
+
   cur->next = new_desg_node(var, desg, assign());
   return cur->next;
 }

tests

@@ -506,6 +506,23 @@ int main() {
   assert(16, ({ int x[]={1,2,3,4}; sizeof(x); }), "int x[]={1,2,3,4}; sizeof(x);");
   assert(4, ({ char x[]="foo"; sizeof(x); }), "char x[]=\"foo\"; sizeof(x); }");
 
+  assert(1, ({ struct {int a; int b; int c;} x={1,2,3}; x.a; }), "struct {int a; int b; int c;} x={1,2,3}; x.a;");
+  assert(2, ({ struct {int a; int b; int c;} x={1,2,3}; x.b; }), "struct {int a; int b; int c;} x={1,2,3}; x.b;");
+  assert(3, ({ struct {int a; int b; int c;} x={1,2,3}; x.c; }), "struct {int a; int b; int c;} x={1,2,3}; x.c;");
+  assert(1, ({ struct {int a; int b; int c;} x={1}; x.a; }), "struct {int a; int b; int c;} x={1}; x.a;");
+  assert(0, ({ struct {int a; int b; int c;} x={1}; x.b; }), "struct {int a; int b; int c;} x={1}; x.b;");
+  assert(0, ({ struct {int a; int b; int c;} x={1}; x.c; }), "struct {int a; int b; int c;} x={1}; x.c;");
+
+  assert(1, ({ struct {int a; int b;} x[2]={{1,2},{3,4}}; x[0].a; }), "struct {int a; int b;} x[2]={{1,2},{3,4}}; x[0].a;");
+  assert(2, ({ struct {int a; int b;} x[2]={{1,2},{3,4}}; x[0].b; }), "struct {int a; int b;} x[2]={{1,2},{3,4}}; x[0].b;");
+  assert(3, ({ struct {int a; int b;} x[2]={{1,2},{3,4}}; x[1].a; }), "struct {int a; int b;} x[2]={{1,2},{3,4}}; x[1].a;");
+  assert(4, ({ struct {int a; int b;} x[2]={{1,2},{3,4}}; x[1].b; }), "struct {int a; int b;} x[2]={{1,2},{3,4}}; x[1].b;");
+
+  assert(0, ({ struct {int a; int b;} x[2]={{1,2}}; x[1].b; }), "struct {int a; int b;} x[2]={{1,2}}; x[1].b;");
+
+  assert(0, ({ struct {int a; int b;} x={}; x.a; }), "struct {int a; int b;} x={}; x.a;");
+  assert(0, ({ struct {int a; int b;} x={}; x.b; }), "struct {int a; int b;} x={}; x.b;");
+
   printf("OK\n");
   return 0;
 }