#74 add support for structs with flexible array member

dibyendumajumdar · Nov 12, 2021 · ae566b2 · ae566b2
1 parent 2d1cc9b
commit ae566b2
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Showing 2 changed files with 50 additions and 19 deletions.
diff --git a/src/codegen.c b/src/codegen.c
@@ -2967,6 +2967,45 @@ static int emit_op_C__unsafe(Function *fn, Instruction *insn)
 	return 0;
 }
 
+static C_Type *get_typeof(Function *fn, C_Scope *global_scope, Pseudo *tagname) {
+	C_Type *ty = hashmap_get(&global_scope->tags, tagname->constant->s->str);
+	if (ty == NULL) {
+		C_VarScope *vc = hashmap_get(&global_scope->vars, tagname->constant->s->str);
+		if (vc && vc->type_def) {
+			ty = vc->type_def;
+		} else {
+			TextBuffer message;
+			raviX_buffer_init(&message, 128);
+			raviX_buffer_add_fstring(&message, "Unknown type '%s'", tagname->constant->s->str);
+			fn->api->error_message(fn->api->context, message.buf);
+			raviX_buffer_free(&message);
+			return NULL;
+		}
+	}
+	return ty;
+}
+
+static C_Member *get_flexible_member(C_Type *type) {
+	if (type->kind != TY_STRUCT)
+		return NULL;
+	C_Member *last_member = NULL;
+	for (C_Member *m = type->members; m != NULL; m = m->next)
+		last_member = m;
+	if (last_member->ty->kind == TY_ARRAY && last_member->ty->array_len == 0) {
+		return last_member;
+	}
+	return NULL;
+}
+
+static void emit_sizeof_expression(Function *fn, const char *main_type, C_Member *flexible_member) {
+	raviX_buffer_add_fstring(&fn->body, "sizeof(%s)", main_type);
+	if (flexible_member != NULL) {
+		raviX_buffer_add_fstring(&fn->body, " + (sizeof ((%s *)0)->%.*s[0])", main_type,
+					 flexible_member->name->len,
+					 flexible_member->name->loc);
+	}
+}
+
 static int emit_op_C__new(Function *fn, Instruction *insn)
 {
 	LinearizerState *linearizer = fn->proc->linearizer;
@@ -2999,23 +3038,10 @@ static int emit_op_C__new(Function *fn, Instruction *insn)
 	Pseudo *size = get_operand(insn, 1);
 	Pseudo *target = get_target(insn, 0);
 	// Add utility in chibicc to find a type
-	C_Type *ty = hashmap_get(&global_scope->tags, tagname->constant->s->str);
-	size_t tagsz = 0;
-	if (ty != NULL) {
-		tagsz = ty->size;
-	} else {
-		C_VarScope *vc = hashmap_get(&global_scope->vars, tagname->constant->s->str);
-		if (vc && vc->type_def) {
-			tagsz = vc->type_def->size;
-		} else {
-			TextBuffer message;
-			raviX_buffer_init(&message, 128);
-			raviX_buffer_add_fstring(&message, "Unknown type '%s'", tagname->constant->s->str);
-			fn->api->error_message(fn->api->context, message.buf);
-			raviX_buffer_free(&message);
-			goto Lexit;
-		}
-	}
+	C_Type *ty = get_typeof(fn, global_scope, tagname);
+	if (ty == NULL)
+		goto Lexit;
+	C_Member *flexible_member = get_flexible_member(ty);
 
 	raviX_buffer_add_string(&fn->body, "{\n");
 	raviX_buffer_add_string(&fn->body, "  TValue *raviX__elements = ");
@@ -3027,7 +3053,10 @@ static int emit_op_C__new(Function *fn, Instruction *insn)
 
 	raviX_buffer_add_string(&fn->body, "  if (ttisinteger(raviX__elements)) {\n");
 	raviX_buffer_add_string(&fn->body, "   lua_Integer n = ivalue(raviX__elements);\n");
-	raviX_buffer_add_fstring(&fn->body, "   Udata *u = luaS_newudata(L, %d * n);\n", (int)tagsz);
+	raviX_buffer_add_fstring(&fn->body, "   size_t raviX__size = ");
+	emit_sizeof_expression(fn, tagname->constant->s->str, flexible_member);
+	raviX_buffer_add_fstring(&fn->body, "* n;\n");
+	raviX_buffer_add_fstring(&fn->body, "   Udata *u = luaS_newudata(L, raviX__size);\n");
 	raviX_buffer_add_string(&fn->body, "   setuvalue(L, raviX__target, u);\n");
 	raviX_buffer_add_string(&fn->body, "  }\n");
 	raviX_buffer_add_string(&fn->body, "  else {\n");

diff --git a/tests/input/t10_embed_C.in b/tests/input/t10_embed_C.in
@@ -1,6 +1,7 @@
 C__decl [[
 typedef struct MyStruct {
-    int a;
+    long a;
+    int variable_length[];
 } MyStruct;
 ]]
 
@@ -9,6 +10,7 @@ function demo(u: Userdata)
     C__unsafe(u) [[
         MyStruct *s = (MyStruct *) u.ptr;
     ]]
+    local u1 = C__new('MyStruct',1)
 
 end
 #