Implement vararg, verify arguments to parameters

14 files changed, 256 insertions, 102 deletions

diff --git a/include/ast.h b/include/ast.h
index 0c34d0b..c45d4aa 100644
--- a/include/ast.h
+++ b/include/ast.h
@@ -132,6 +132,12 @@ struct Scope {
     FunctionSignature *function_signature; /* Borrowed from FunctionDecl. Only used if the scope belongs to FunctionDecl */
 };
 
+typedef enum {
+    VARIABLE_TYPE_FLAG_NONE      = 0,
+    VARIABLE_TYPE_FLAG_OPTIONAL  = 1 << 0,
+    VARIABLE_TYPE_FLAG_BORROW    = 1 << 1
+} VariableTypeFlag;
+
 typedef struct {
     enum {
         VARIABLE_TYPE_NONE,
@@ -143,6 +149,7 @@ typedef struct {
         Variable *variable;
         FunctionSignature *signature;
     } value;
+    VariableTypeFlag variable_type_flags;
 } VariableType;
 
 struct FileScopeReference {
diff --git a/include/bytecode/bytecode.h b/include/bytecode/bytecode.h
index 8f786a2..23bc4cf 100644
--- a/include/bytecode/bytecode.h
+++ b/include/bytecode/bytecode.h
@@ -77,7 +77,8 @@ typedef enum {
 
 typedef enum {
     FUNC_FLAG_NONE       = 0,
-    FUNC_FLAG_EXPORTED   = 1 << 0
+    FUNC_FLAG_EXPORTED   = 1 << 0,
+    FUNC_FLAG_VARARGS    = 1 << 1
 } amal_func_flag;
 
 typedef u8 AmalOpcodeType;
@@ -110,10 +111,13 @@ typedef struct {
 #pragma pack(push, 1)
 typedef struct {
     u8 num_params;
+    u8 num_return_types;
+    u8 name_len;
+    u8 flags;
+
     u32 params_num_pointers;
     u32 params_fixed_size;
 
-    u8 num_return_types;
     u32 return_types_num_pointers;
     u32 return_types_fixed_size;
 } BytecodeHeaderExternFunction;
diff --git a/include/compiler.h b/include/compiler.h
index f6599a1..164cf4e 100644
--- a/include/compiler.h
+++ b/include/compiler.h
@@ -15,7 +15,7 @@
 #define AMAL_COMPILER_ERR -1
 #define AMAL_COMPILER_WORK_FAIL_ABORT -2
 
-#define NUM_ARITHMETIC_TYPES 10
+#define NUM_ARITHMETIC_TYPES 14
 
 typedef struct {
     LhsExpr lhs_expr;
@@ -42,6 +42,7 @@ typedef struct {
     amal_default_type *c_int;
     amal_default_type *c_long;
     amal_default_type *c_void;
+    amal_default_type *c_varargs;
 
     amal_default_type *str;
 
diff --git a/include/program.h b/include/program.h
index aa318d9..dc65cb7 100644
--- a/include/program.h
+++ b/include/program.h
@@ -38,13 +38,11 @@
 #define AMAL_PROGRAM_INVALID_IMPORTS -26
 #define AMAL_PROGRAM_SECTION_ERROR -27
 
-#define AMAL_PROGRAM_ARGS_SIZE_VARARGS -1
-
 #define AMAL_PROGRAM_MAX_RETURN_VALUES 128
 
 typedef struct {
     void *func;
-    int args_byte_size; /* -1 if varargs (AMAL_PROGRAM_ARGS_SIZE_VARARGS) */
+    u32 args_byte_size;
 } ProgramExternFunc;
 
 typedef struct {
@@ -81,9 +79,10 @@ void amal_program_deinit(amal_program *self);
 
 /*
     returns @AMAL_PROGRAM_EXTERN_FUNC_ALREADY_EXISTS if a function with the name @name already exists
-    in the program
+    in the program.
+    If the function has a vararg parameter, then @args_byte_size should be the minimum parameters size excluding the varargs.
 */
-CHECK_RESULT int amal_program_register_extern_func(amal_program *self, BufferView name, void *func_ptr, int args_byte_size);
+CHECK_RESULT int amal_program_register_extern_func(amal_program *self, BufferView name, void *func_ptr, u32 args_byte_size);
 
 CHECK_RESULT int amal_program_append_bytecode(amal_program *self, Bytecode *bytecode);
 CHECK_RESULT int amal_program_run(amal_program *self);
diff --git a/include/tokenizer.h b/include/tokenizer.h
index b6b401b..53351a4 100644
--- a/include/tokenizer.h
+++ b/include/tokenizer.h
@@ -40,7 +40,9 @@ typedef enum {
     TOK_WHILE,
     TOK_EXTERN,
     TOK_EXPORT,
-    TOK_RETURN
+    TOK_RETURN,
+    TOK_QUESTION_MARK,
+    TOK_C_VARARGS
 } Token;
 
 struct Tokenizer {
diff --git a/src/ast.c b/src/ast.c
index 0008785..90af981 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -5,6 +5,7 @@
 #include "../include/std/hash.h"
 #include <assert.h>
 #include <stdarg.h>
+#include <stdio.h>
 
 #define throw(result) do { throw_debug_msg; longjmp(context->env, (result)); } while(0)
 #define throw_if_error(result) \
@@ -446,6 +447,8 @@ static void compiler_print_error(amal_compiler *compiler, const char *ref, const
     tokenizer = amal_compiler_find_tokenizer_by_code_reference(compiler, ref);
     if(!tokenizer) {
         amal_log_error("Failed to find tokenizer for code reference %p. Is it an invalid reference?", ref ? ref : "(null)");
+        vfprintf(stderr, fmt, args);
+        fputc('\n', stderr);
         return;
     }
     tokenizer_print_error_args(tokenizer, tokenizer_get_code_reference_index(tokenizer, ref), fmt, args);
@@ -726,9 +729,60 @@ static void funcdecl_resolve(Ast *self, AstCompilerContext *context) {
     self->resolve_data.type.value.func_sig = self->value.func_decl->signature;
 }
 
+static usize min(usize a, usize b) {
+    return a < b ? a : b;
+}
+
+static bool resolve_data_type_equals(AstResolvedType *self, AstResolvedType *other) {
+    return self->type == other->type && self->value.data == other->value.data;
+}
+
+static bool function_parameter_is_vararg(FunctionParameter *self, AstCompilerContext *context) {
+    amal_default_type *vararg_type = context->compiler->default_types.c_varargs;
+    return self->resolve_data.type.value.data == &vararg_type->lhs_expr;
+}
+
+static void verify_func_call_matches_func_signature(FunctionCall *func_call, FunctionSignature *func_sig, AstCompilerContext *context) {
+    Ast **arg = buffer_begin(&func_call->args);
+    Ast **arg_end = buffer_end(&func_call->args);
+
+    FunctionParameter *func_param = buffer_begin(&func_sig->parameters);
+    FunctionParameter *func_param_end = buffer_end(&func_sig->parameters);
+    
+    usize num_args = arg_end - arg;
+    usize num_params = func_param_end - func_param;
+    isize num_missing_args = (isize)num_params - (isize)num_args;
+    usize num_check = min(num_args, num_params);
+    usize i = 0;
+    for(; i < num_check; ++i) {
+        if(!resolve_data_type_equals(&(*arg)->resolve_data.type, &func_param->resolve_data.type) && !function_parameter_is_vararg(func_param, context)) {
+            BufferView arg_name = ast_resolved_type_get_name(&(*arg)->resolve_data.type);
+            BufferView param_name = ast_resolved_type_get_name(&func_param->resolve_data.type);
+            compiler_print_error(context->compiler, func_call->func.name.data,
+                "Can't cast argument of type \"%.*s\" to parameter of type \"%.*s\"", arg_name.size, arg_name.data, param_name.size, param_name.data);
+            throw(AST_ERR);
+        }
+        ++arg;
+        ++func_param;
+    }
+
+    if(num_missing_args > 0) {
+        FunctionParameter *vararg_param = buffer_begin(&func_sig->parameters);
+        bool has_vararg = num_params > 0 && function_parameter_is_vararg(&vararg_param[num_params - 1], context);
+        if (has_vararg)
+            num_missing_args -= 1;
+        if(num_missing_args > 0) {
+            compiler_print_error(context->compiler, func_call->func.name.data,
+                "Missing %d argument(s) to closure \"%.*s\"", num_missing_args, func_call->func.name.size, func_call->func.name.data);
+            throw(AST_ERR);
+        }
+    }
+}
+
 static void funccall_resolve(Ast *self, AstCompilerContext *context) {
     Ast **ast;
     Ast **ast_end;
+    FunctionSignature *func_sig;
 
     FunctionCall *func_call = self->value.func_call;
     variable_resolve(&func_call->func, context, &self->resolve_data.type);
@@ -744,7 +798,7 @@ static void funccall_resolve(Ast *self, AstCompilerContext *context) {
     }
 
     {
-        FunctionSignature *func_sig = self->resolve_data.type.value.func_sig;
+        func_sig = self->resolve_data.type.value.func_sig;
         FunctionReturnType *return_type = buffer_begin(&func_sig->return_types);
         assert(buffer_get_size(&func_sig->return_types, FunctionReturnType) == 1);
         self->resolve_data.type.type = RESOLVED_TYPE_LHS_EXPR;
@@ -756,6 +810,8 @@ static void funccall_resolve(Ast *self, AstCompilerContext *context) {
     for(; ast != ast_end; ++ast) {
         ast_resolve(*ast, context);
     }
+
+    verify_func_call_matches_func_signature(func_call, func_sig, context);
 }
 
 static TypeSize variable_type_get_byte_size(VariableType *self) {
@@ -766,9 +822,13 @@ static TypeSize variable_type_get_byte_size(VariableType *self) {
         case VARIABLE_TYPE_NONE:
             assert(bool_false && "Variable type not resolved!");
             break;
-        case VARIABLE_TYPE_VARIABLE:
-            type_size = resolved_type_get_byte_size(&self->value.variable->resolved_var.resolve_data->type);
+        case VARIABLE_TYPE_VARIABLE: {
+            if(self->variable_type_flags & VARIABLE_TYPE_FLAG_BORROW)
+                type_size.num_pointers = 1;
+            else
+                type_size = resolved_type_get_byte_size(&self->value.variable->resolved_var.resolve_data->type);
             break;
+        }
         case VARIABLE_TYPE_SIGNATURE:
             type_size.num_pointers = 1;
             break;
@@ -790,7 +850,8 @@ static void structdecl_resolve(Ast *self, AstCompilerContext *context) {
         Ast **ast = buffer_begin(&body->ast_objects);
         Ast **ast_end = buffer_end(&body->ast_objects);
         for(; ast != ast_end; ++ast) {
-            TypeSize type_size = variable_type_get_byte_size(&(*ast)->value.struct_field->type);
+            StructField *struct_field = (*ast)->value.struct_field;
+            TypeSize type_size = variable_type_get_byte_size(&struct_field->type);
             struct_decl->fields_num_pointers += type_size.num_pointers;
             struct_decl->fields_fixed_size_bytes += type_size.fixed_size;
         }
@@ -1020,9 +1081,9 @@ void ast_resolve(Ast *self, AstCompilerContext *context) {
             /* TODO: Support other number types */
             self->resolve_data.type.type = RESOLVED_TYPE_LHS_EXPR;
             if(number->is_integer)
-                self->resolve_data.type.value.lhs_expr = (LhsExpr*)context->compiler->default_types.i64;
+                self->resolve_data.type.value.lhs_expr = &context->compiler->default_types.i64->lhs_expr;
             else
-                self->resolve_data.type.value.lhs_expr = (LhsExpr*)context->compiler->default_types.f64;
+                self->resolve_data.type.value.lhs_expr = &context->compiler->default_types.f64->lhs_expr;
             break;
         }
         case AST_FUNCTION_DECL:
@@ -1050,7 +1111,7 @@ void ast_resolve(Ast *self, AstCompilerContext *context) {
         case AST_STRING:
             /* TODO: Convert special combinations. For example \n to newline */
             self->resolve_data.type.type = RESOLVED_TYPE_LHS_EXPR;
-            self->resolve_data.type.value.lhs_expr = (LhsExpr*)context->compiler->default_types.str;
+            self->resolve_data.type.value.lhs_expr = &context->compiler->default_types.str->lhs_expr;
             break;
         case AST_VARIABLE:
             variable_resolve(self->value.variable, context, &self->resolve_data.type);
diff --git a/src/bytecode/bytecode.c b/src/bytecode/bytecode.c
index 7dbc305..a5e3abc 100644
--- a/src/bytecode/bytecode.c
+++ b/src/bytecode/bytecode.c
@@ -142,9 +142,13 @@ static TypeSize function_signature_get_params_size(FunctionSignature *self) {
     params_total_size.num_pointers = 0;
     params_total_size.fixed_size = 0;
     for(; param != param_end; ++param) {
-        TypeSize param_size = resolved_type_get_byte_size(&param->resolve_data.type);
-        params_total_size.num_pointers += param_size.num_pointers;
-        params_total_size.fixed_size += param_size.fixed_size;
+        if(param->type.variable_type_flags & VARIABLE_TYPE_FLAG_BORROW)
+            params_total_size.num_pointers += 1;
+        else {
+            TypeSize param_size = resolved_type_get_byte_size(&param->resolve_data.type);
+            params_total_size.num_pointers += param_size.num_pointers;
+            params_total_size.fixed_size += param_size.fixed_size;
+        }
     }
     return params_total_size;
 }
@@ -228,20 +232,21 @@ static void add_extern_functions(BytecodeCompilerContext *self) {
         |Type|Field                    |Description                                                                                          |
         |----|-------------------------|-----------------------------------------------------------------------------------------------------|
         |u8  |num_params               |The number of parameters.                                                                            |
+        |u8  |num_return_types         |The number of return values.                                                                         |
+        |u8  |name_len                 |The length of the external function name, in bytes. Excluding the null-terminate character.          |
+        |u8  |flags                    |The flags for the external function. The values are defined in @amal_func_flag.                      |
         |u32 |params_num_pointers      |The number of pointers in the parameters.                                                            |
         |u32 |params_fixed_size        |The size of all non-pointer type parameters, in bytes.                                               |
-        |u8  |num_return_types         |The number of return values.                                                                         |
         |u32 |return_types_num_pointers|The number of pointers in the return types.                                                          |
         |u32 |return_types_fixed_size  |The size of all non-pointer type return types, in bytes.                                             |
-        |u8  |name_len                 |The length of the external function name, in bytes. Excluding the null-terminate character.          |
         |u8[]|name                     |The name of the external function, where the size is defined by @name_len. Names are null-terminated.|
     */
     Ssa *ssa = self->parser->ssa;
     Buffer *instructions = &self->bytecode->data;
     SsaExternFunc *extern_func = buffer_begin(&ssa->extern_funcs);
     SsaExternFunc *extern_func_end = buffer_end(&ssa->extern_funcs);
-    u32 extern_funcs_size = (u32)ssa->extern_func_counter * (sizeof(BytecodeHeaderExternFunction) + sizeof(u8));
-    assert(sizeof(BytecodeHeaderExternFunction) == 18);
+    u32 extern_funcs_size = (u32)ssa->extern_func_counter * sizeof(BytecodeHeaderExternFunction);
+    assert(sizeof(BytecodeHeaderExternFunction) == 20);
 
     for(; extern_func != extern_func_end; ++extern_func) {
         extern_funcs_size += extern_func->name.size + 1; /* +1 for null-termination of string */
@@ -259,17 +264,26 @@ static void add_extern_functions(BytecodeCompilerContext *self) {
         BytecodeHeaderExternFunction header_func;
 
         header_func.num_params = buffer_get_size(&extern_func->func_sig->parameters, FunctionParameter);
+        header_func.num_return_types = buffer_get_size(&extern_func->func_sig->return_types, FunctionReturnType);
+        header_func.name_len = extern_func->name.size;
+        header_func.flags = 0;
+        if(header_func.num_params > 0) {
+            amal_default_type *vararg_type = self->parser->compiler->default_types.c_varargs;
+            FunctionParameter *last_param = buffer_begin(&extern_func->func_sig->parameters);
+            last_param += (header_func.num_params - 1);
+            if(last_param->resolve_data.type.value.data == &vararg_type->lhs_expr)
+                header_func.flags |= FUNC_FLAG_VARARGS;
+        }
+
         header_func.params_num_pointers = params_total_size.num_pointers;
         header_func.params_fixed_size = params_total_size.fixed_size;
 
-        header_func.num_return_types = buffer_get_size(&extern_func->func_sig->return_types, FunctionReturnType);
         header_func.return_types_num_pointers = return_types_total_size.num_pointers;
         header_func.return_types_fixed_size = return_types_total_size.fixed_size;
         throw_if_error(buffer_append(instructions, &header_func, sizeof(header_func)));
 
         /* TODO: Add namespace to the function name */
         /* u8 is fine, because the max length of a variable is 255 */
-        throw_if_error(buffer_append(instructions, &extern_func->name.size, sizeof(u8)));
         throw_if_error(buffer_append(instructions, extern_func->name.data, extern_func->name.size));
         throw_if_error(buffer_append(instructions, &null_s, sizeof(char)));
     }
@@ -435,10 +449,10 @@ static void add_ins6(BytecodeCompilerContext *self, AmalOpcode opcode, i8 dst_re
 static void add_instructions(BytecodeCompilerContext *self) {
     /*doc(Bytecode instructions)
         # Instructions layout
-        |Type       |Field            |Description                                                                |
-        |-----------|-----------------|---------------------------------------------------------------------------|
-        |u32        |Instructions size|The size of the instructions section, in bytes.                            |
-        |Instruction|Instructions data|The instructions data. Each instructions begins with an opcode, see #Opcode|
+        |Type         |Field            |Description                                                                |
+        |-------------|-----------------|---------------------------------------------------------------------------|
+        |u32          |Instructions size|The size of the instructions section, in bytes.                            |
+        |Instruction[]|Instructions data|The instructions data. Each instructions begins with an opcode, see #Opcode|
     */
 
     SsaInsForm1 ssa_ins_form1;
diff --git a/src/compiler.c b/src/compiler.c
index 4d43329..5b48aaf 100644
--- a/src/compiler.c
+++ b/src/compiler.c
@@ -82,6 +82,7 @@ static CHECK_RESULT int init_default_types(amal_compiler *compiler) {
     return_if_error(create_default_type_fixed_size(compiler, "c_int", sizeof(int), &compiler->default_types.c_int));
     return_if_error(create_default_type_fixed_size(compiler, "c_long", sizeof(long), &compiler->default_types.c_long));
     return_if_error(create_default_type_num_pointers(compiler, "c_void", 0, &compiler->default_types.c_void));
+    return_if_error(create_default_type_num_pointers(compiler, "...", 0, &compiler->default_types.c_varargs));
 
     compiler->default_types.arithmetic_types[0] = compiler->default_types.i8;
     compiler->default_types.arithmetic_types[1] = compiler->default_types.u8;
@@ -94,6 +95,11 @@ static CHECK_RESULT int init_default_types(amal_compiler *compiler) {
     compiler->default_types.arithmetic_types[8] = compiler->default_types.isize;
     compiler->default_types.arithmetic_types[9] = compiler->default_types.usize;
 
+    compiler->default_types.arithmetic_types[10] = compiler->default_types.c_char;
+    compiler->default_types.arithmetic_types[11] = compiler->default_types.c_short;
+    compiler->default_types.arithmetic_types[12] = compiler->default_types.c_int;
+    compiler->default_types.arithmetic_types[13] = compiler->default_types.c_long;
+
     compiler->default_types.i8->is_signed = bool_true;
     compiler->default_types.u8->is_signed = bool_false;
     compiler->default_types.i16->is_signed = bool_true;
@@ -106,7 +112,15 @@ static CHECK_RESULT int init_default_types(amal_compiler *compiler) {
     compiler->default_types.usize->is_signed = bool_false;
     compiler->default_types.f32->is_signed = bool_true;
     compiler->default_types.f64->is_signed = bool_true;
+    compiler->default_types.bool->is_signed = bool_false;
     compiler->default_types.str->is_signed = bool_false;
+
+    compiler->default_types.c_char->is_signed = bool_true;
+    compiler->default_types.c_short->is_signed = bool_true;
+    compiler->default_types.c_int->is_signed = bool_true;
+    compiler->default_types.c_long->is_signed = bool_true;
+    compiler->default_types.c_void->is_signed = bool_false;
+    compiler->default_types.c_varargs->is_signed = bool_false;
     return 0;
 }
 
@@ -199,8 +213,10 @@ static CHECK_RESULT int amal_compiler_load_in_this_thread(amal_compiler *compile
     parser_allocator = NULL;
     result = AMAL_COMPILER_ERR;
 
-    return_if_error(arena_allocator_alloc(&compiler->allocator, sizeof(ArenaAllocator), (void**)&parser_allocator));
+    cleanup_if_error(amal_mutex_lock(&compiler->mutex, "amal_compiler_load_in_this_thread, create allocator for parser"));
+    cleanup_if_error(arena_allocator_alloc(&compiler->allocator, sizeof(ArenaAllocator), (void**)&parser_allocator));
     cleanup_if_error(arena_allocator_init(parser_allocator));
+    amal_mutex_tryunlock(&compiler->mutex);
 
     filepath = create_buffer_view(file_scope->canonical_path.data, file_scope->canonical_path.size);
     amal_log_info("Started parsing %.*s", filepath.size, filepath.data);
diff --git a/src/parser.c b/src/parser.c
index 9da9147..dc39a6a 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -119,31 +119,45 @@ static void parser_parse_struct_body_loop(Parser *self, StructDecl *struct_decl)
 }
 
 /*
-FUNC_PARAM = TOK_IDENTIFIER VAR_TYPE_DEF
+FUNC_PARAM = (TOK_IDENTIFIER VAR_TYPE_DEF)|'...'
 */
 static CHECK_RESULT bool parser_parse_function_parameter(Parser *self, FunctionParameter *result) {
     bool match;
 
     throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_IDENTIFIER, &match));
-    if(!match)
-        return bool_false;
+    if(match) {
+        result->name = self->tokenizer.value.identifier;
+        parser_parse_var_type_def(self, &result->type);
+        if(result->type.type == VARIABLE_TYPE_NONE) {
+            self->error = tokenizer_create_error(&self->tokenizer,
+                                                 tokenizer_get_error_index(&self->tokenizer),
+                                                 "Expected ':' after parameter name");
+            throw(PARSER_UNEXPECTED_TOKEN);
+        }
+        return bool_true;
+    }
 
-    result->name = self->tokenizer.value.identifier;
-    parser_parse_var_type_def(self, &result->type);
-    if(result->type.type == VARIABLE_TYPE_NONE) {
-        self->error = tokenizer_create_error(&self->tokenizer,
-                                             tokenizer_get_error_index(&self->tokenizer),
-                                             "Expected ':' after parameter name");
-        throw(PARSER_UNEXPECTED_TOKEN);
+    throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_C_VARARGS, &match));
+    if(match) {
+        result->name = self->tokenizer.value.identifier;
+        result->type.variable_type_flags = VARIABLE_TYPE_FLAG_NONE;
+        result->type.type = VARIABLE_TYPE_VARIABLE;
+        throw_if_error(arena_allocator_alloc(self->allocator, sizeof(Variable), (void**)&result->type.value.variable));
+        variable_init(result->type.value.variable, result->name);
+        return bool_true;
     }
 
-    return bool_true;
+    return bool_false;
 }
 
 /*
 FUNC_PARAMS = FUNC_PARAM (',' FUNC_PARAM)*
 */
 static void parser_parse_function_parameters(Parser *self, FunctionSignature *func_sig) {
+    amal_default_type *vararg_type = self->compiler->default_types.c_varargs;
+    int vararg_index = -1;
+    int index = 0;
+
     for(;;) {
         FunctionParameter func_param;
         bool match;
@@ -157,6 +171,13 @@ static void parser_parse_function_parameters(Parser *self, FunctionSignature *fu
             throw(PARSER_UNEXPECTED_TOKEN);
         }
 
+        if(vararg_index != -1) {
+            self->error = tokenizer_create_error(&self->tokenizer,
+                                                 tokenizer_get_error_index(&self->tokenizer),
+                                                 "A closure can't have parameters after a vararg");
+            throw(PARSER_UNEXPECTED_TOKEN);
+        }
+
         result = function_signature_add_parameter(func_sig, &func_param);
         if(result == AST_ERR_DEF_DUP) {
             self->error = tokenizer_create_error(&self->tokenizer, 
@@ -169,7 +190,19 @@ static void parser_parse_function_parameters(Parser *self, FunctionSignature *fu
         }
         throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_COMMA, &match));
         if(!match)
-            return;
+            break;
+
+        if (vararg_index == -1 && buffer_view_equals(&func_param.name, &vararg_type->lhs_expr.var_name))
+            vararg_index = index;
+
+        ++index;
+    }
+
+    if (index > FUNC_MAX_PARAMS) {
+        self->error = tokenizer_create_error(&self->tokenizer,
+                                             tokenizer_get_error_index(&self->tokenizer),
+                                             "A closure can't have more than %d parameters", FUNC_MAX_PARAMS);
+        throw(PARSER_ERR);
     }
 }
 
@@ -192,19 +225,19 @@ static void parser_parse_function_return_types(Parser *self, FunctionSignature *
                                                  tokenizer_get_error_index(&self->tokenizer),
                                                  "Expected type or closure signature");
             throw(PARSER_UNEXPECTED_TOKEN);
+        } else if(var_type.variable_type_flags & VARIABLE_TYPE_FLAG_BORROW) {
+            self->error = tokenizer_create_error(&self->tokenizer,
+                                                 tokenizer_get_error_index(&self->tokenizer),
+                                                 "A closure can't return a value as borrowed");
+            throw(PARSER_ERR);
         }
+
         throw_if_error(function_signature_add_return_type(func_sig, &var_type));
         throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_COMMA, &match));
         if(!match)
             break;
-        ++return_type_index;
-    }
 
-    if (buffer_get_size(&func_sig->parameters, FunctionParameter) > FUNC_MAX_PARAMS) {
-        self->error = tokenizer_create_error(&self->tokenizer,
-                                             tokenizer_get_error_index(&self->tokenizer),
-                                             "A closure can't have more than %d parameters", FUNC_MAX_PARAMS);
-        throw(PARSER_ERR);
+        ++return_type_index;
     }
 
     if (buffer_get_size(&func_sig->return_types, FunctionReturnType) > FUNC_MAX_RETURN_TYPES) {
@@ -244,13 +277,27 @@ static CHECK_RESULT FunctionSignature* parser_parse_function_signature(Parser *s
 }
 
 /*
-VAR_TYPE = TOK_IDENTIFIER|FUNC_SIGNATURE
+VAR_TYPE = '?'? TOK_IDENTIFIER|FUNC_SIGNATURE
 */
 void parser_parse_var_type(Parser *self, VariableType *result) {
     bool match;
 
     result->type = VARIABLE_TYPE_NONE;
     result->value.variable = NULL;
+    result->variable_type_flags = VARIABLE_TYPE_FLAG_NONE;
+
+    throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_QUESTION_MARK, &match));
+    if(match) 
+        result->variable_type_flags |= VARIABLE_TYPE_FLAG_OPTIONAL;
+
+    throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_BINOP, &match));
+    if(match) {
+        if(self->tokenizer.value.binop_type != BINOP_MUL) {
+            self->error = tokenizer_create_error(&self->tokenizer, tokenizer_get_error_index(&self->tokenizer), "Expected '*', type or closure signature");
+            throw(PARSER_UNEXPECTED_TOKEN);
+        }
+        result->variable_type_flags |= VARIABLE_TYPE_FLAG_BORROW;
+    }
 
     throw_if_error(tokenizer_consume_if(&self->tokenizer, TOK_IDENTIFIER, &match));
     if(match) {
diff --git a/src/program.c b/src/program.c
index 128f0f9..4c0f1a2 100644
--- a/src/program.c
+++ b/src/program.c
@@ -78,7 +78,7 @@ void amal_program_deinit(amal_program *self) {
         buffer_deinit(&self->data);
 }
 
-int amal_program_register_extern_func(amal_program *self, BufferView name, void *func_ptr, int args_byte_size) {
+int amal_program_register_extern_func(amal_program *self, BufferView name, void *func_ptr, u32 args_byte_size) {
     ProgramExternFunc extern_func;
     extern_func.func = func_ptr;
     extern_func.args_byte_size = args_byte_size;
@@ -112,15 +112,16 @@ static void amal_program_get_header_extern_function_by_index(amal_program *self,
     u32 i;
     u8 *extern_funcs_start = amal_program_get_extern_funcs_start_by_import_index(self, import_index);
     extern_funcs_start += sizeof(u16) + sizeof(u32);
+
     for(i = 0; i < (u32)index; ++i) {
-        u8 name_len;
+        BytecodeHeaderExternFunction *extern_func = (BytecodeHeaderExternFunction*)extern_funcs_start;
         extern_funcs_start += sizeof(BytecodeHeaderExternFunction);
-        name_len = *extern_funcs_start;
-        extern_funcs_start += 1 + name_len + 1; /* +1 for skipping length byte and the null-terminated character */
+        extern_funcs_start += extern_func->name_len + 1; /* +1 for skipping the null-terminated character */
     }
+
     am_memcpy(&result->extern_func, extern_funcs_start, sizeof(result->extern_func));
-    result->name.size = *(extern_funcs_start + sizeof(result->extern_func));
-    result->name.data = (const char*)extern_funcs_start + sizeof(result->extern_func) + sizeof(u8);
+    result->name.size = result->extern_func.name_len;
+    result->name.data = (const char*)extern_funcs_start + sizeof(result->extern_func);
 }
 
 
@@ -133,10 +134,15 @@ static CHECK_RESULT int amal_program_get_extern_func_by_index(amal_program *self
         return AMAL_PROGRAM_NO_SUCH_EXTERNAL_FUNCTION;
     }
     
-    /* TODO: This assumes all arguments are of size sizeof(isize) */
-    if(result->args_byte_size != -1 && result->args_byte_size != (int)extern_func_get_total_param_size(&extern_func.extern_func)) {
-        amal_log_error("Extern function %.*s was registered to take %d byte(s), but the program says it takes %d byte(s)",
-            extern_func.name.size, extern_func.name.data, result->args_byte_size, (int)extern_func_get_total_param_size(&extern_func.extern_func));
+    if(extern_func.extern_func.flags & FUNC_FLAG_VARARGS) {
+        if(extern_func_get_total_param_size(&extern_func.extern_func) < result->args_byte_size) {
+            amal_log_error("Extern function %.*s was registered to take at least %u byte(s), but the program says it takes at least %u byte(s)",
+                extern_func.name.size, extern_func.name.data, result->args_byte_size, extern_func_get_total_param_size(&extern_func.extern_func));
+            return AMAL_PROGRAM_NO_SUCH_EXTERNAL_FUNCTION;
+        }
+    } else if(extern_func_get_total_param_size(&extern_func.extern_func) != result->args_byte_size) {
+        amal_log_error("Extern function %.*s was registered to take %u byte(s), but the program says it takes %u byte(s)",
+            extern_func.name.size, extern_func.name.data, result->args_byte_size, extern_func_get_total_param_size(&extern_func.extern_func));
         return AMAL_PROGRAM_NO_SUCH_EXTERNAL_FUNCTION;
     }
     return 0;
diff --git a/src/tokenizer.c b/src/tokenizer.c
index 9ce1bba..d753b20 100644
--- a/src/tokenizer.c
+++ b/src/tokenizer.c
@@ -235,19 +235,6 @@ static CHECK_RESULT int __tokenizer_next(Tokenizer *self, Token *token) {
             }
         }
         *token = TOK_IDENTIFIER;
-    } else if(c == '"') {
-        int string_end;
-        ++self->index;
-        string_end = find_end_of_string(self->code, self->index);
-        if(string_end == -1) {
-            tokenizer_print_error(self, self->prev_index, "String end not found. Did you forget '\"' or did you have a mismatch of number of '\"'?");
-            return TOKENIZER_ERR;
-        }
-
-        self->value.string.data = &self->code.data[self->index];
-        self->value.string.size = string_end - self->index;
-        self->index = string_end + 1;
-        *token = TOK_STRING;
     } else if(isDigit(c)) {
         int number_start;
         int dot_index;
@@ -290,9 +277,31 @@ static CHECK_RESULT int __tokenizer_next(Tokenizer *self, Token *token) {
             self->number_is_integer = bool_false;
         }
         *token = TOK_NUMBER;
+    } else if(c == '"') {
+        int string_end;
+        ++self->index;
+        string_end = find_end_of_string(self->code, self->index);
+        if(string_end == -1) {
+            tokenizer_print_error(self, self->prev_index, "String end not found. Did you forget '\"' or did you have a mismatch of number of '\"'?");
+            return TOKENIZER_ERR;
+        }
+
+        self->value.string.data = &self->code.data[self->index];
+        self->value.string.size = string_end - self->index;
+        self->index = string_end + 1;
+        *token = TOK_STRING;
     } else if(c == '.') {
+        const char *start = self->code.data + self->index;
         ++self->index;
-        SET_BINOP(BINOP_DOT);
+        /* ... */
+        if((usize)self->index + 2 < self->code.size && am_memcmp(self->code.data + self->index, "..", 2) == 0) {
+            self->index += 2;
+            self->value.identifier.data = start;
+            self->value.identifier.size = 3;
+            *token = TOK_C_VARARGS;
+        } else {
+            SET_BINOP(BINOP_DOT);
+        }
     } else if(c == '+') {
         ++self->index;
         SET_BINOP(BINOP_ADD);
@@ -351,6 +360,9 @@ static CHECK_RESULT int __tokenizer_next(Tokenizer *self, Token *token) {
     } else if(c == ':') {
         ++self->index;
         *token = TOK_COLON;
+    } else if(c == '?') {
+        ++self->index;
+        *token = TOK_QUESTION_MARK;
     } else if(c == '@') {
         const char *err_msg;
         ++self->index;
@@ -502,6 +514,12 @@ static BufferView tokenizer_expected_token_as_string(Token token) {
         case TOK_RETURN:
             str = "return";
             break;
+        case TOK_QUESTION_MARK:
+            str = "?";
+            break;
+        case TOK_C_VARARGS:
+            str = "...";
+            break;
     }
     return create_buffer_view(str, strlen(str));
 }
diff --git a/tests/bytecode.amal b/tests/bytecode.amal
index 6941bc8..d27a240 100644
--- a/tests/bytecode.amal
+++ b/tests/bytecode.amal
@@ -1,31 +1,5 @@
-/*
-extern const print_extern: fn() i32;
-extern const print_extern_num: fn(num: i32) i32;
+extern const printf: fn(fmt: ?*c_char, ...) c_int;
 
-const print = fn() i32 {
-    return 0;
-}
-
-const main = fn {
-    var value = 23;
-    value = 34;
-    const value2: i64 = 54;
-    const value3 = 2 + 5 - 1 * 10 / 2;
-    const str_value = "hello, world";
-    print();
-    if value2 == 54
-        const result = print_num(1337);
-}
-
-const print_num = fn(num: i32) i32 {
-    print_extern();
-    print_extern_num(num);
-    print_extern_num(8080);
-    return num;
-}
-*/
-
-const io = @import("../std/io.amal");
 const main = fn {
-    io.print();
+    printf("hello, world!\n");
 }
diff --git a/tests/errors/return_borrow.amal b/tests/errors/return_borrow.amal
new file mode 100644
index 0000000..ed1a043
--- /dev/null
+++ b/tests/errors/return_borrow.amal
@@ -0,0 +1 @@
+const func = fn() *str {}
\ No newline at end of file
diff --git a/tests/main.c b/tests/main.c
index 019f8d9..0b3a744 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -251,6 +251,10 @@ static void test_load(const char *filepath) {
         fprintf(stderr, "Unexpected error (alloc failure)\n");
         FAIL_TEST_CLEANUP(full_path);
     }
+    if(amal_program_register_extern_func(&program, create_buffer_view_auto("printf"), printf, sizeof(const char*)) != 0) {
+        fprintf(stderr, "Unexpected error (alloc failure)\n");
+        FAIL_TEST_CLEANUP(full_path);
+    }
 
     result = amal_compiler_load_file(&options, &program, filepath);
     if(result != AMAL_COMPILER_OK) {