c variadic calls

LANGUAGE.md

@@ -34,6 +34,7 @@
 - file-local relative imports, aliases, and qualified member access
 - relative `.h` imports as synthetic package namespaces
 - transitive external C function prototypes, typedef chains, C scalars, and pointers to opaque C records
+- bodyless manual and imported C variadic declarations with target-aware default argument promotions
 - reference-time diagnostics for unsupported imported C declarations
 
 ### compiler behavior
@@ -50,7 +51,6 @@
 
 ### foreign functions and linking
 
-- c variadic calls with default argument promotions
 - exporting brolang functions to c
 
 ### scalar and compound types

README.md

@@ -45,6 +45,18 @@ pointers to opaque records. They never add linker inputs; implementations must
 still be supplied explicitly with the C-prefixed linking options. Set
 `BROLANG_LIBCLANG_PATH` when libclang is not installed in a standard location.
 
+Bodyless manual and imported C functions may be variadic:
+
+```bro
+log_values :: c_func(tag c_int, ...) c_int
+```
+
+Arguments after `...` accept concrete scalars, pointers, and nullable pointers.
+Narrow integers are promoted to the target C `int` or `unsigned int`, and
+`f32`/`c_float` are promoted to `c_double`. Arrays, slices, structs, and other
+compound values must be converted to an explicit C-compatible representation
+before the call.
+
 Compilation phases are isolated under `compiler/`:
 
 ```text
@@ -83,6 +95,7 @@ Current prototype features:
 - Qualified imported globals and functions with package-aware symbol mangling
 - Demand-monomorphized Brolang and C-ABI functions
 - Bodyless concrete C function declarations with exact external symbol names
+- Bodyless manual and imported C variadic declarations with default argument promotions
 - Ordered linking of additional C sources, objects, archives, and libraries
 - Checked signed addition and unary negation
 - Static, eager runtime, and deferred problematic globals

TODO.md

@@ -38,7 +38,7 @@
    - diagnose unsupported declarations when referenced
    - dynamically load libclang behind a replaceable c importer boundary
 
-3. c variadic calls
+3. c variadic calls (implemented)
    - represent c variadics as a fixed parameter count plus a variadic flag
    - apply c default argument promotions at call sites
    - emit LLVM c-variadic declarations and calls

compiler/ast/ast.odin

@@ -130,6 +130,7 @@ Function :: struct {
 	c_abi:      bool,
 	imported:   bool,
 	has_body:   bool,
+	variadic:   bool,
 	params:     []Param,
 	result:     Type_Syntax,
 	body:       []Stmt_Id,

compiler/checker/checker.odin

@@ -454,7 +454,7 @@ add_unsupported_type_diagnostic :: proc(
 }
 
 function_signatures_equal :: proc(left, right: ast.Function) -> bool {
-	if left.result != right.result || len(left.params) != len(right.params) {
+	if left.result != right.result || left.variadic != right.variadic || len(left.params) != len(right.params) {
 		return false
 	}
 	for param, index in left.params {
@@ -465,6 +465,17 @@ function_signatures_equal :: proc(left, right: ast.Function) -> bool {
 	return true
 }
 
+valid_call_arity :: proc(function: ast.Function, count: int) -> bool {
+	return count >= len(function.params) if function.variadic else count == len(function.params)
+}
+
+call_arg_expected :: proc(function: ast.Function, index: int) -> types.Type {
+	if index < 0 || index >= len(function.params) {
+		return types.INVALID
+	}
+	return type_from_syntax(function.params[index].type)
+}
+
 contains_name :: proc(names: []symbol.Id, name: symbol.Id) -> bool {
 	for existing in names {
 		if existing == name {
@@ -566,6 +577,14 @@ validate_declarations :: proc(checker: ^Checker) {
 				symbol_text(checker, function.name),
 			)
 		}
+		if function.variadic && (!function.c_abi || function.has_body) {
+			checker.template_diagnostics[function_id] = source.addf(
+				checker.diagnostics,
+				function.span,
+				"variadic function '%s' must be a bodyless 'c_func' declaration",
+				symbol_text(checker, function.name),
+			)
+		}
 		if !function.has_body && function.c_abi {
 			for param in function.params {
 				if add_unsupported_type_diagnostic(checker, param.span, type_from_syntax(param.type)) !=
@@ -1029,11 +1048,12 @@ infer_expr :: proc(
 				}
 			}
 			function := checker.ast_module.functions[frame.template]
-			if can_specialize(checker, function, stack[frame_index].args) {
+			if valid_call_arity(function, len(expr.args)) &&
+			   can_specialize(checker, function, stack[frame_index].args) {
 				spec := INVALID_SPEC
 				if demanded == nil {
 					spec = ensure_spec(checker, frame.template, stack[frame_index].args)
-				} else if len(expr.args) == len(function.params) {
+				} else {
 					spec = find_spec(checker, frame.template, stack[frame_index].args)
 					mark_spec_demanded(checker, spec, demanded)
 				}
@@ -1317,6 +1337,32 @@ coerce_expr :: proc(
 	return invalid_hir_expr(checker, span, id, expected)
 }
 
+promote_c_vararg_expr :: proc(checker: ^Checker, expr_id: hir.Expr_Id, span: source.Span) -> hir.Expr_Id {
+	actual := checker.module.exprs[expr_id].type
+	if !types.is_c_vararg_type(actual, &checker.module.types) {
+		id := source.addf(
+			checker.diagnostics,
+			span,
+			"C variadic argument must be a concrete scalar or pointer, got %s",
+			types.name(actual),
+		)
+		return invalid_hir_expr(checker, span, id, types.C_INT)
+	}
+	promoted := types.c_vararg_promotion(actual, checker.target)
+	if types.equal(actual, promoted) {
+		return expr_id
+	}
+	return add_hir_expr(checker, hir.Expr{
+		kind=.C_Vararg_Promote,
+		span=span,
+		type=promoted,
+		left=expr_id,
+		target=hir.INVALID_REF,
+		right=hir.INVALID_EXPR,
+		diagnostic=source.INVALID_DIAGNOSTIC,
+	})
+}
+
 build_constant_expr :: proc(
 	checker: ^Checker,
 	expr: ast.Expr,
@@ -1891,13 +1937,16 @@ build_expr :: proc(
 					_ = pop(&stack)
 					continue
 				}
-				if len(expr.args) != len(checker.ast_module.functions[template].params) {
+				function := checker.ast_module.functions[template]
+				if !valid_call_arity(function, len(expr.args)) {
+					message := "function '%s' expects at least %d arguments, got %d" if function.variadic else
+					           "function '%s' expects %d arguments, got %d"
 					id := source.addf(
 						checker.diagnostics,
 						expr.span,
-						"function '%s' expects %d arguments, got %d",
+						message,
 						symbol_text(checker, expr.name),
-						len(checker.ast_module.functions[template].params),
+						len(function.params),
 						len(expr.args),
 					)
 					last = invalid_hir_expr(checker, expr.span, id)
@@ -1909,7 +1958,7 @@ build_expr :: proc(
 				stack[frame_index].arg_types = make([]types.Type, len(expr.args), checker.allocator)
 				stack[frame_index].stage = 3
 				if len(expr.args) > 0 {
-					arg_expected := type_from_syntax(checker.ast_module.functions[template].params[0].type)
+					arg_expected := call_arg_expected(function, 0)
 					if !is_runtime_type(checker, arg_expected) {
 						arg_expected = types.INVALID
 					}
@@ -1980,7 +2029,7 @@ build_expr :: proc(
 				stack[frame_index].arg_index += 1
 				if frame.arg_index+1 < len(expr.args) {
 					next := frame.arg_index+1
-					arg_expected := type_from_syntax(checker.ast_module.functions[frame.template].params[next].type)
+					arg_expected := call_arg_expected(checker.ast_module.functions[frame.template], next)
 					if !is_runtime_type(checker, arg_expected) {
 						arg_expected = types.INVALID
 					}
@@ -2004,7 +2053,8 @@ build_expr :: proc(
 				_ = pop(&stack)
 				continue
 			}
-			for _, index in stack[frame_index].built_args {
+			fixed_count := len(checker.ast_module.functions[frame.template].params)
+			for index in 0..<fixed_count {
 				stack[frame_index].built_args[index] = coerce_expr(
 					checker,
 					stack[frame_index].built_args[index],
@@ -2012,6 +2062,14 @@ build_expr :: proc(
 					checker.module.exprs[stack[frame_index].built_args[index]].span,
 				)
 			}
+			for index in fixed_count..<len(stack[frame_index].built_args) {
+				arg := stack[frame_index].built_args[index]
+				stack[frame_index].built_args[index] = promote_c_vararg_expr(
+					checker,
+					arg,
+					checker.module.exprs[arg].span,
+				)
+			}
 			function_id := checker.specs[spec].hir_id
 			assert(function_id != hir.INVALID_FUNCTION)
 			add_unique_function(calls, function_id)
@@ -2128,6 +2186,7 @@ build_function :: proc(checker: ^Checker, id: Spec_Id) {
 				implementation = .Declaration,
 				linkage = .External if function.c_abi else .Internal,
 				is_main = function.pkg == 0 && function.name == checker.main_symbol,
+				variadic = function.variadic,
 				params = params[:],
 				result = spec.result,
 				locals = hir_locals[:],
@@ -2524,6 +2583,7 @@ build_function :: proc(checker: ^Checker, id: Spec_Id) {
 			implementation = .Definition,
 			linkage = .External if function.c_abi || (function.pkg == 0 && function.name == checker.main_symbol) else .Internal,
 			is_main = function.pkg == 0 && function.name == checker.main_symbol,
+			variadic = function.variadic,
 			params = params[:],
 			result = spec.result,
 			locals = hir_locals[:],

compiler/cimport/cimport.odin

@@ -46,10 +46,11 @@ Alias :: struct {
 }
 
 Function :: struct {
-	name:   string,
-	params: []Type_Id,
-	result: Type_Id,
-	reason: string,
+	name:     string,
+	params:   []Type_Id,
+	result:   Type_Id,
+	variadic: bool,
+	reason:   string,
 }
 
 Unsupported :: struct {

compiler/cimport/libclang.odin

@@ -338,9 +338,8 @@ visit_cursor :: proc "c"(cursor, parent: CXCursor, client_data: rawptr) -> i32 {
 		linkage := ctx.api.get_cursor_linkage(cursor)
 		if linkage != CXLinkage_External {
 			reason = "static and non-external C functions are not supported"
-		} else if ctx.api.cursor_is_variadic(cursor) != 0 {
-			reason = "C variadic functions are not supported"
 		}
+		variadic := ctx.api.cursor_is_variadic(cursor) != 0
 		function_type := ctx.api.get_cursor_type(cursor)
 		result_type := translate_type(ctx, ctx.api.get_result_type(function_type))
 		if result_type == INVALID_TYPE && len(reason) == 0 {
@@ -364,6 +363,7 @@ visit_cursor :: proc "c"(cursor, parent: CXCursor, client_data: rawptr) -> i32 {
 			name=fmt.aprintf("%s", name, allocator=ctx.allocator),
 			params=params[:],
 			result=result_type,
+			variadic=variadic,
 			reason=fmt.aprintf("%s", reason, allocator=ctx.allocator),
 		})
 	case CXCursor_TypedefDecl:

compiler/hir/hir.odin

@@ -93,6 +93,7 @@ Expr_Kind :: enum u8 {
 	Unwrap,
 	Orelse,
 	Widen,
+	C_Vararg_Promote,
 	Weaken_Pointer,
 	Negate,
 	Add,
@@ -144,6 +145,7 @@ Function :: struct {
 	implementation:      Implementation,
 	linkage:             Linkage,
 	is_main:             bool,
+	variadic:            bool,
 	params:              []Local_Id,
 	result:              types.Type,
 	locals:              []Local,

compiler/ir/ir.odin

@@ -87,6 +87,7 @@ Opcode :: enum u8 {
 	Orelse_Begin,
 	Orelse,
 	Widen,
+	C_Vararg_Promote,
 	Weaken_Pointer,
 	Neg_Checked,
 	Add_Checked,
@@ -115,6 +116,7 @@ Function :: struct {
 	implementation:     Implementation,
 	linkage:            Linkage,
 	is_main:            bool,
+	variadic:           bool,
 	param_types:        []types.Type,
 	result:             types.Type,
 	instructions:       []Instruction,

compiler/lexer/lexer.odin

@@ -119,7 +119,12 @@ lex :: proc(
 			cursor += 1
 			if cursor < len(bytes) && bytes[cursor] == '.' {
 				cursor += 1
-				append_token(&stream, source_file, .Range, start, cursor)
+				if cursor < len(bytes) && bytes[cursor] == '.' {
+					cursor += 1
+					append_token(&stream, source_file, .Ellipsis, start, cursor)
+				} else {
+					append_token(&stream, source_file, .Range, start, cursor)
+				}
 			} else {
 				append_token(&stream, source_file, .Dot, start, cursor)
 			}

compiler/llvm/llvm.odin

@@ -112,7 +112,7 @@ valid_value :: proc(
 	switch instructions[value_id].op {
 	case .Param, .Const, .String, .Aggregate, .None, .Optional_Some,
 	     .Load_Global, .Address_Of, .Load, .Slice, .Length, .Slice_Ptr, .Unwrap, .Orelse,
-	     .Widen, .Weaken_Pointer, .Neg_Checked, .Add_Checked, .Pointer_Add, .Call:
+	     .Widen, .C_Vararg_Promote, .Weaken_Pointer, .Neg_Checked, .Add_Checked, .Pointer_Add, .Call:
 		return true
 	case .Address_Global, .Alloca, .Index_Address, .Field_Address, .Orelse_Begin,
 	     .Store, .Trap, .Return, .Return_Void:
@@ -275,14 +275,16 @@ emit_call_args :: proc(
 		if index > 0 {
 			strings.write_string(builder, ", ")
 		}
-		fmt.sbprintf(builder, "%s ", llvm_type(param_types[index], store))
-		if c_abi {
-			extension := c_abi_extension(param_types[index], store.selected)
+		arg_type := param_types[index] if index < len(param_types) && valid_instruction(instructions, arg) else
+		            (instructions[arg].type if valid_instruction(instructions, arg) else types.INVALID)
+		fmt.sbprintf(builder, "%s ", llvm_type(arg_type, store))
+		if c_abi && index < len(param_types) {
+			extension := c_abi_extension(arg_type, store.selected)
 			if len(extension) > 0 {
 				fmt.sbprintf(builder, "%s ", extension)
 			}
 		}
-		write_operand(builder, instructions, arg, param_types[index], store)
+		write_operand(builder, instructions, arg, arg_type, store)
 	}
 }
 
@@ -707,6 +709,31 @@ emit_instruction_stream :: proc(
 			fmt.sbprintf(&emitter.builder, "  %%v%d = %s %s ", instruction_index, operation, llvm_type(from_type, &emitter.module.types))
 			write_operand(&emitter.builder, instructions, instruction.a, from_type, &emitter.module.types)
 			fmt.sbprintf(&emitter.builder, " to %s\n", llvm_type(instruction.type, &emitter.module.types))
+		case .C_Vararg_Promote:
+			if !valid_instruction(instructions, instruction.a) {
+				emit_recovery_value(emitter, instruction_index, instruction, "invalid C variadic promotion operand")
+				continue
+			}
+			from_type := instructions[instruction.a].type
+			if types.equal(from_type, instruction.type) ||
+			   !types.equal(types.c_vararg_promotion(from_type, emitter.module.target), instruction.type) {
+				emit_recovery_value(emitter, instruction_index, instruction, "invalid C variadic promotion operand")
+				continue
+			}
+			if types.bits(from_type, emitter.module.target) == types.bits(instruction.type, emitter.module.target) {
+				type_name := llvm_type(instruction.type, &emitter.module.types)
+				fmt.sbprintf(&emitter.builder, "  %%v%d = select i1 true, %s ", instruction_index, type_name)
+				write_operand(&emitter.builder, instructions, instruction.a, from_type, &emitter.module.types)
+				fmt.sbprintf(&emitter.builder, ", %s ", type_name)
+				write_operand(&emitter.builder, instructions, instruction.a, from_type, &emitter.module.types)
+				strings.write_string(&emitter.builder, "\n")
+				continue
+			}
+			operation := "fpext" if types.is_float(from_type, emitter.module.target) else
+			             ("sext" if types.is_signed(from_type, emitter.module.target) else "zext")
+			fmt.sbprintf(&emitter.builder, "  %%v%d = %s %s ", instruction_index, operation, llvm_type(from_type, &emitter.module.types))
+			write_operand(&emitter.builder, instructions, instruction.a, from_type, &emitter.module.types)
+			fmt.sbprintf(&emitter.builder, " to %s\n", llvm_type(instruction.type, &emitter.module.types))
 		case .Weaken_Pointer:
 			if !valid_instruction(instructions, instruction.a) ||
 			   !types.can_weaken_pointer(instructions[instruction.a].type, instruction.type, &emitter.module.types) {
@@ -806,10 +833,20 @@ emit_instruction_stream :: proc(
 				continue
 			}
 			target := emitter.module.functions[function_id]
-			valid_args := len(instruction.args) == len(target.param_types)
+			valid_args := (len(instruction.args) >= len(target.param_types) if target.variadic else
+			               len(instruction.args) == len(target.param_types)) &&
+			              (!target.variadic || target.calling_convention == .C)
 			if valid_args {
 				for arg, index in instruction.args {
-					if !valid_value(instructions, arg, target.param_types[index], &emitter.module.types) {
+					expected := target.param_types[index] if index < len(target.param_types) && valid_instruction(instructions, arg) else
+					            (instructions[arg].type if valid_instruction(instructions, arg) else types.INVALID)
+					if index >= len(target.param_types) &&
+					   (!types.is_c_vararg_type(expected, &emitter.module.types) ||
+					    !types.equal(types.c_vararg_promotion(expected, emitter.module.target), expected)) {
+						valid_args = false
+						break
+					}
+					if !valid_value(instructions, arg, expected, &emitter.module.types) {
 						valid_args = false
 						break
 					}
@@ -833,6 +870,19 @@ emit_instruction_stream :: proc(
 				strings.write_string(&emitter.builder, "fastcc ")
 			}
 			emit_function_result(&emitter.builder, target, &emitter.module.types)
+			if target.variadic {
+				strings.write_string(&emitter.builder, " (")
+				for param_type, index in target.param_types {
+					if index > 0 {
+						strings.write_string(&emitter.builder, ", ")
+					}
+					strings.write_string(&emitter.builder, llvm_type(param_type, &emitter.module.types))
+				}
+				if len(target.param_types) > 0 {
+					strings.write_string(&emitter.builder, ", ")
+				}
+				strings.write_string(&emitter.builder, "...)")
+			}
 			fmt.sbprintf(&emitter.builder, " @%s(", target.link_name)
 			emit_call_args(
 				&emitter.builder, instructions, instruction.args, target.param_types,
@@ -1037,6 +1087,12 @@ emit_functions :: proc(emitter: ^Emitter) {
 				fmt.sbprintf(&emitter.builder, " %%v%d", index)
 			}
 		}
+		if function.variadic {
+			if len(function.param_types) > 0 {
+				strings.write_string(&emitter.builder, ", ")
+			}
+			strings.write_string(&emitter.builder, "...")
+		}
 		if function.implementation == .Declaration {
 			strings.write_string(&emitter.builder, ")\n\n")
 			continue

compiler/loader/loader.odin

@@ -177,8 +177,8 @@ translate_c_type :: proc(
 	return translated
 }
 
-function_signatures_equal :: proc(left: ast.Function, params: []ast.Param, result: types.Type) -> bool {
-	if left.result != result || len(left.params) != len(params) {
+function_signatures_equal :: proc(left: ast.Function, params: []ast.Param, result: types.Type, variadic: bool) -> bool {
+	if left.result != result || left.variadic != variadic || len(left.params) != len(params) {
 		return false
 	}
 	for param, index in params {
@@ -282,7 +282,7 @@ load_header :: proc(state: ^State, path: string, import_span: source.Span) -> as
 				continue
 			}
 			duplicate = true
-			if !function_signatures_equal(existing, params, function_result) && len(existing.unsupported_reason) == 0 {
+			if !function_signatures_equal(existing, params, function_result, function.variadic) && len(existing.unsupported_reason) == 0 {
 				existing.unsupported_reason = fmt.aprintf(
 					"conflicting C declarations for '%s'",
 					function.name,
@@ -303,6 +303,7 @@ load_header :: proc(state: ^State, path: string, import_span: source.Span) -> as
 			c_abi=true,
 			imported=true,
 			has_body=false,
+			variadic=function.variadic,
 			params=params,
 			result=function_result,
 			unsupported_reason=strings.clone(unsupported_reason, state.allocator),

compiler/lower/lower.odin

@@ -324,7 +324,7 @@ lower_expr :: proc(state: ^State, expr_id: hir.Expr_Id) -> ir.Instruction_Id {
 					})
 				}
 				_ = pop(&stack)
-			case .Widen, .Weaken_Pointer:
+			case .Widen, .C_Vararg_Promote, .Weaken_Pointer:
 				stack[frame_index].stage = 1
 				append(&stack, Lower_Expr_Frame{expr=expr.left})
 			case .Negate:
@@ -358,7 +358,8 @@ lower_expr :: proc(state: ^State, expr_id: hir.Expr_Id) -> ir.Instruction_Id {
 		}
 		if frame.stage == 1 {
 			last = append_instruction(state, ir.Instruction{
-				op=.Weaken_Pointer if expr.kind == .Weaken_Pointer else .Widen,
+				op=.Weaken_Pointer if expr.kind == .Weaken_Pointer else
+				   (.C_Vararg_Promote if expr.kind == .C_Vararg_Promote else .Widen),
 				span=expr.span, type=expr.type, target=ir.INVALID_REF,
 				a=last, b=ir.INVALID_INSTRUCTION, diagnostic=source.INVALID_DIAGNOSTIC,
 			})
@@ -611,6 +612,7 @@ lower :: proc(hir_module: ^hir.Module, allocator := context.allocator) -> ir.Mod
 			implementation=.Declaration if function.implementation == .Declaration else .Definition,
 			linkage=.External if function.linkage == .External else .Internal,
 			is_main=function.is_main,
+			variadic=function.variadic,
 			param_types=param_types,
 			result=function.result,
 			instructions=nil if function.implementation == .Declaration else lower_body(hir_module, function, allocator),

compiler/parser/parser.odin

@@ -889,11 +889,27 @@ parse_statement :: proc(parser: ^Parser) -> ast.Stmt_Id {
 	return id
 }
 
-parse_params :: proc(parser: ^Parser) -> []ast.Param {
+parse_params :: proc(parser: ^Parser) -> ([]ast.Param, bool) {
 	params: [dynamic]ast.Param
 	params.allocator = parser.module.allocator
+	variadic := false
 	skip_newlines(parser)
 	for current(parser).kind != .Right_Paren && current(parser).kind != .Eof {
+		if current(parser).kind == .Ellipsis {
+			marker := advance(parser)
+			if variadic {
+				source.add(parser.diagnostics, marker.span, "duplicate variadic marker")
+			}
+			variadic = true
+			skip_newlines(parser)
+			if _, ok := allow(parser, .Comma); ok {
+				skip_newlines(parser)
+			}
+			if current(parser).kind != .Right_Paren {
+				source.add(parser.diagnostics, current(parser).span, "variadic marker must be the final parameter")
+			}
+			continue
+		}
 		names: [dynamic]token.Token
 		names.allocator = parser.module.allocator
 		for {
@@ -923,7 +939,7 @@ parse_params :: proc(parser: ^Parser) -> []ast.Param {
 		}
 		break
 	}
-	return params[:]
+	return params[:], variadic
 }
 
 parse_function :: proc(parser: ^Parser, name: token.Token, c_abi: bool) {
@@ -931,7 +947,7 @@ parse_function :: proc(parser: ^Parser, name: token.Token, c_abi: bool) {
 	if _, ok := allow(parser, .Left_Paren); !ok {
 		source.add(parser.diagnostics, current(parser).span, "expected '(' after 'func'")
 	}
-	params := parse_params(parser)
+	params, variadic := parse_params(parser)
 	if _, ok := allow(parser, .Right_Paren); !ok {
 		source.add(parser.diagnostics, current(parser).span, "expected ')' after parameters")
 	}
@@ -954,6 +970,7 @@ parse_function :: proc(parser: ^Parser, name: token.Token, c_abi: bool) {
 			file=parser.file,
 			c_abi=c_abi,
 			has_body=false,
+			variadic=variadic,
 			params=params,
 			result=result,
 			diagnostic=source.INVALID_DIAGNOSTIC,
@@ -991,6 +1008,7 @@ parse_function :: proc(parser: ^Parser, name: token.Token, c_abi: bool) {
 		file=parser.file,
 		c_abi=c_abi,
 		has_body=true,
+		variadic=variadic,
 		params=params,
 		result=result,
 		body=body[:],

compiler/token/token.odin

@@ -19,6 +19,7 @@ Kind :: enum u8 {
 	Minus,
 	Dot,
 	Range,
+	Ellipsis,
 	At,
 	Star,
 	Ampersand,

compiler/types/types.odin

@@ -432,6 +432,34 @@ is_c_signature_type :: proc(value: Type, store: ^Store, allow_void := false) ->
 	return is_concrete_scalar(value) || is_pointer(value, store) || is_optional_pointer(value, store)
 }
 
+is_c_integer_promotion_candidate :: proc(value: Type) -> bool {
+	return value >= C_CHAR && value <= C_USHORT
+}
+
+c_vararg_promotion :: proc(value: Type, selected := target.DEFAULT) -> Type {
+	if !is_concrete_scalar(value) {
+		return value
+	}
+	if is_float(value, selected) && bits(value, selected) < bits(C_DOUBLE, selected) {
+		return C_DOUBLE
+	}
+	if is_concrete_integer(value) {
+		value_bits := bits(value, selected)
+		int_bits := bits(C_INT, selected)
+		if value_bits < int_bits {
+			return C_INT
+		}
+		if is_c_integer_promotion_candidate(value) && value_bits == int_bits {
+			return C_INT if is_signed(value, selected) else C_UINT
+		}
+	}
+	return value
+}
+
+is_c_vararg_type :: proc(value: Type, store: ^Store) -> bool {
+	return is_concrete_scalar(value) || is_pointer(value, store) || is_optional_pointer(value, store)
+}
+
 child_type :: proc(value: Type, store: ^Store) -> Type {
 	item, ok := node(store, value)
 	return item.child if ok else INVALID

compiler_tests.odin

@@ -229,6 +229,38 @@ main :: func() void {}
 	testing.expect(t, module.functions[3].has_body)
 }
 
+@(test)
+parser_accepts_terminal_c_variadic_markers_and_recovers_nonterminal_markers :: proc(t: ^testing.T) {
+	text := `fixed :: c_func(value c_int, ...) c_int
+zero :: c_func(...) void
+bad :: c_func(..., value c_int) c_int
+main :: func() void {}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&module)
+
+	found_ellipsis := false
+	for tok in stream.items {
+		found_ellipsis = found_ellipsis || tok.kind == .Ellipsis
+	}
+	testing.expect(t, found_ellipsis)
+	testing.expect(t, module.functions[0].variadic)
+	testing.expect_value(t, len(module.functions[0].params), 1)
+	testing.expect(t, module.functions[1].variadic)
+	testing.expect_value(t, len(module.functions[1].params), 0)
+	testing.expect(t, module.functions[2].variadic)
+	testing.expect_value(t, len(module.functions[2].params), 1)
+	testing.expect_value(t, len(diagnostics.items), 1)
+	testing.expect(t, strings.contains(diagnostics.items[0].message, "final parameter"))
+}
+
 @(test)
 parser_treats_c_as_contextual_only_before_func :: proc(t: ^testing.T) {
 	text := `c :: 5
@@ -680,6 +712,14 @@ c_primitives_remain_distinct_with_apple_silicon_representations :: proc(t: ^test
 	testing.expect_value(t, types.representation(types.C_FLOAT), types.F32)
 	testing.expect_value(t, types.representation(types.C_DOUBLE), types.F64)
 	testing.expect_value(t, types.representation(types.C_LONGDOUBLE), types.F64)
+	testing.expect_value(t, types.c_vararg_promotion(types.I8), types.C_INT)
+	testing.expect_value(t, types.c_vararg_promotion(types.U16), types.C_INT)
+	testing.expect_value(t, types.c_vararg_promotion(types.C_CHAR), types.C_INT)
+	testing.expect_value(t, types.c_vararg_promotion(types.C_USHORT), types.C_INT)
+	testing.expect_value(t, types.c_vararg_promotion(types.F32), types.C_DOUBLE)
+	testing.expect_value(t, types.c_vararg_promotion(types.C_FLOAT), types.C_DOUBLE)
+	testing.expect_value(t, types.c_vararg_promotion(types.U32), types.U32)
+	testing.expect_value(t, types.c_vararg_promotion(types.C_DOUBLE), types.C_DOUBLE)
 	testing.expect_value(t, target.llvm_triple(target.DEFAULT), "arm64-apple-macosx13.0.0")
 }
 
@@ -744,6 +784,113 @@ main :: func() void {
 	testing.expect(t, strings.contains(llvm_text, "orelse_some"))
 }
 
+@(test)
+c_variadic_calls_promote_extras_and_emit_variadic_llvm :: proc(t: ^testing.T) {
+text := `variadic :: c_func(tag c_int, ...) c_int
+zero :: c_func(...) void
+main :: func() void {
+	narrow i8 :: -2
+	unsigned u16 :: 3
+	float_value f32 :: 4.0
+	c_float_value c_float :: 5.0
+	pointer *u8 :: "ok".ptr
+	nullable ?*u8 :: pointer
+	zero(pointer)
+	_ = variadic(7, narrow, unsigned, float_value, c_float_value, pointer, nullable)
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+	ir_module := lower.lower(&hir_module)
+	defer ir.destroy_module(&ir_module)
+	llvm_text := llvm.emit(&ir_module, &diagnostics, &symbols)
+	defer delete(llvm_text)
+
+	promotions := 0
+	for expr in hir_module.exprs {
+		if expr.kind == .C_Vararg_Promote {
+			promotions += 1
+		}
+	}
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect_value(t, promotions, 4)
+	found_hir_variadic := false
+	for function in hir_module.functions {
+		found_hir_variadic = found_hir_variadic || function.variadic
+	}
+	found_ir_variadic := false
+	for function in ir_module.functions {
+		found_ir_variadic = found_ir_variadic || function.variadic
+	}
+	testing.expect(t, found_hir_variadic)
+	testing.expect(t, found_ir_variadic)
+	testing.expect(t, strings.contains(llvm_text, "declare i32 @variadic(i32, ...)"))
+	testing.expect(t, strings.contains(llvm_text, "declare void @zero(...)"))
+	testing.expect(t, strings.contains(llvm_text, "sext i8"))
+	testing.expect(t, strings.contains(llvm_text, "zext i16"))
+	testing.expect(t, strings.contains(llvm_text, "fpext float"))
+	testing.expect(t, strings.contains(llvm_text, "call void (...) @zero(ptr"))
+	testing.expect(t, strings.contains(llvm_text, "call i32 (i32, ...) @variadic(i32 7, i32"))
+	testing.expect(t, strings.contains(llvm_text, "double"))
+	testing.expect(t, strings.contains(llvm_text, "ptr"))
+}
+
+@(test)
+c_variadic_restrictions_and_extra_argument_types_are_diagnosed :: proc(t: ^testing.T) {
+	text := `foreign :: c_func(...) void
+requires :: c_func(value c_int, ...) void
+native :: func(...) void
+bodyful :: c_func(...) void {}
+main :: func() void {
+	values [1]u8 :: [1]
+	foreign(values)
+	requires()
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	restricted := 0
+	found_extra := false
+	found_arity := false
+	for diagnostic in diagnostics.items {
+		if strings.contains(diagnostic.message, "must be a bodyless 'c_func' declaration") {
+			restricted += 1
+		}
+		found_extra = found_extra || strings.contains(diagnostic.message, "C variadic argument must be a concrete scalar or pointer")
+		found_arity = found_arity || strings.contains(diagnostic.message, "expects at least 1 arguments")
+	}
+	testing.expect_value(t, restricted, 2)
+	testing.expect(t, found_extra)
+	testing.expect(t, found_arity)
+}
+
+@(test)
+variadicness_is_part_of_c_function_signature_compatibility :: proc(t: ^testing.T) {
+	fixed := ast.Function{result=types.C_INT}
+	variadic := ast.Function{result=types.C_INT, variadic=true}
+	testing.expect(t, !checker.function_signatures_equal(fixed, variadic))
+	testing.expect(t, !loader.function_signatures_equal(fixed, nil, types.C_INT, true))
+}
+
 @(test)
 c_structs_are_pointer_only_and_may_be_opaque :: proc(t: ^testing.T) {
 	text := `Defined :: c_struct {
@@ -1683,6 +1830,7 @@ fake_cimport_backend :: proc(user_data: rawptr, request: cimport.Request, alloca
 	append(&result.functions, cimport.Function{
 		name=fmt.aprintf("fake_value", allocator=allocator),
 		result=cimport.Type_Id(0),
+		variadic=true,
 		reason=fmt.aprintf("", allocator=allocator),
 	})
 	result.available = true
@@ -1700,6 +1848,7 @@ cimport_backend_is_replaceable :: proc(t: ^testing.T) {
 	testing.expect_value(t, state.calls, 1)
 	testing.expect_value(t, len(result.functions), 1)
 	testing.expect_value(t, result.functions[0].name, "fake_value")
+	testing.expect(t, result.functions[0].variadic)
 }
 
 @(test)
@@ -1732,6 +1881,11 @@ loader_injects_and_caches_cimport_backend_per_compilation :: proc(t: ^testing.T)
 	testing.expect_value(t, len(module.imports), 2)
 	testing.expect_value(t, module.imports[0].target, module.imports[1].target)
 	testing.expect_value(t, len(module.functions), 2)
+	found_variadic := false
+	for function in module.functions {
+		found_variadic = found_variadic || function.variadic
+	}
+	testing.expect(t, found_variadic)
 }
 
 @(test)

examples/interop/header/app/main.bro

@@ -10,4 +10,11 @@ main :: func() void {
 	_ = native.child_value(7)
 	_ = native.imported_read(native.imported_handle()?)
 	_ = native.configured_value(9)
+	signed i8 :: -2
+	unsigned u16 :: 3
+	float_value f32 :: 4.0
+	c_float_value c_float :: 5.0
+	pointer *u8 :: "ok".ptr
+	nullable ?*u8 :: pointer
+	_ = native.imported_variadic(7, signed, unsigned, float_value, c_float_value, pointer, nullable)
 }

examples/interop/header/include/native.h

@@ -35,6 +35,6 @@ int configured_value(int value);
 #endif
 
 #define IMPORTED_MACRO 42
-int imported_variadic(const char *format, ...);
+int imported_variadic(int marker, ...);
 
 #endif

examples/interop/header/native.c

@@ -1,4 +1,6 @@
 #include "include/native.h"
+#include <stdarg.h>
+#include <stdlib.h>
 
 struct Imported_Handle {
 	int value;
@@ -26,6 +28,28 @@ int imported_read(const Imported_Handle *value) {
 	return value->value;
 }
 
+int imported_variadic(int marker, ...) {
+	va_list args;
+	va_start(args, marker);
+	int narrow_signed = va_arg(args, int);
+	int narrow_unsigned = va_arg(args, int);
+	double float_value = va_arg(args, double);
+	double c_float_value = va_arg(args, double);
+	const unsigned char *pointer = va_arg(args, const unsigned char *);
+	const unsigned char *nullable = va_arg(args, const unsigned char *);
+	va_end(args);
+	if (!(marker == 7 &&
+	      narrow_signed == -2 &&
+	      narrow_unsigned == 3 &&
+	      float_value == 4.0 &&
+	      c_float_value == 5.0 &&
+	      pointer[0] == 'o' &&
+	      nullable == pointer)) {
+		abort();
+	}
+	return 0;
+}
+
 #ifdef BROLANG_FEATURE
 int configured_value(int value) {
 	return value;

examples/interop/header_unsupported/main.bro

@@ -5,7 +5,6 @@ use_union :: c_func(value native.Imported_Union) void
 use_enum :: c_func(value native.Imported_Enum) void
 
 main :: func() void {
-	_ = native.imported_variadic("value")
 	_ = native.IMPORTED_MACRO
 	_ = native.imported_by_value()
 	_ = native.imported_volatile()