c bool support and c-integer coercion

compiler/checker/checker.odin

@@ -1882,6 +1882,20 @@ coerce_expr :: proc(
 			},
 		)
 	}
+	if types.can_coerce_c_integer(actual, expected) {
+		return add_hir_expr(
+			checker,
+			hir.Expr {
+				kind = .C_Coerce,
+				span = span,
+				type = expected,
+				left = expr_id,
+				target = hir.INVALID_REF,
+				right = hir.INVALID_EXPR,
+				diagnostic = source.INVALID_DIAGNOSTIC,
+			},
+		)
+	}
 	id := source.addf(
 		checker.diagnostics,
 		span,

compiler/cimport/cimport.odin

@@ -9,6 +9,7 @@ INVALID_TYPE :: Type_Id(0xffff_ffff)
 Type_Kind :: enum u8 {
 	Invalid,
 	Void,
+	C_Bool,
 	C_Char,
 	C_Schar,
 	C_Uchar,

compiler/cimport/libclang.odin

@@ -132,6 +132,7 @@ CXTLS_None :: i32(0)
 CXType_Invalid :: i32(0)
 CXType_Unexposed :: i32(1)
 CXType_Void :: i32(2)
+CXType_Bool :: i32(3)
 CXType_Char_U :: i32(4)
 CXType_UChar :: i32(5)
 CXType_UShort :: i32(8)
@@ -435,6 +436,7 @@ translate_type :: proc(ctx: ^Context, value: CXType, preferred_record_name := ""
 	}
 	switch value.kind {
 	case CXType_Void:       return add_type(ctx, Type{kind=.Void, child=INVALID_TYPE})
+	case CXType_Bool:       return add_type(ctx, Type{kind=.C_Bool, child=INVALID_TYPE})
 	case CXType_Char_U:     return add_type(ctx, Type{kind=.C_Char, child=INVALID_TYPE})
 	case CXType_Char_S:     return add_type(ctx, Type{kind=.C_Char, child=INVALID_TYPE})
 	case CXType_SChar:      return add_type(ctx, Type{kind=.C_Schar, child=INVALID_TYPE})

compiler/hir/hir.odin

@@ -95,6 +95,7 @@ Expr_Kind :: enum u8 {
 	Unwrap,
 	Orelse,
 	Widen,
+	C_Coerce,
 	C_Vararg_Promote,
 	Retype,
 	Weaken_Pointer,

compiler/ir/ir.odin

@@ -92,6 +92,7 @@ Opcode :: enum u8 {
 	Orelse_Begin,
 	Orelse,
 	Widen,
+	C_Coerce,
 	C_Vararg_Promote,
 	Retype,
 	Weaken_Pointer,

compiler/llvm/llvm.odin

@@ -191,6 +191,10 @@ function_result_type :: proc(function: ir.Function, store: ^types.Store) -> stri
 
 c_abi_extension :: proc(value: types.Type, store: ^types.Store) -> string {
 	resolved := types.runtime_representation(value, store)
+	if types.is_bool(resolved) {
+		// clang lowers C `_Bool` as `zeroext i1` across the ABI boundary.
+		return "zeroext"
+	}
 	if !types.is_concrete_integer(resolved) {
 		return ""
 	}
@@ -252,7 +256,7 @@ valid_value :: proc(
 	     .Load_Global, .Function_Address, .Address_Of, .Load, .Slice, .Length, .Slice_Ptr,
 	     .Extract, .Select, .Unwrap,
 	     .Optional_Is_Some, .Optional_Value, .Orelse,
-	     .Widen, .C_Vararg_Promote, .Retype, .Weaken_Pointer, .Weaken_Slice, .Decay_Array_Pointer,
+	     .Widen, .C_Coerce, .C_Vararg_Promote, .Retype, .Weaken_Pointer, .Weaken_Slice, .Decay_Array_Pointer,
 	     .Neg_Checked, .Add_Checked, .Sub_Checked, .Mul_Checked, .Div_Checked, .Pointer_Add, .Not, .Compare, .Call:
 		return true
 	case .Address_Global, .Alloca, .Index_Address, .Field_Address, .Orelse_Begin,
@@ -297,19 +301,15 @@ write_constant :: proc(builder: ^strings.Builder, value: i64, value_type: types.
 	}
 	selected := store.selected if store != nil else target.DEFAULT
 	if types.is_float(resolved, selected) {
-		text := ""
+		// LLVM rejects decimal float literals that don't round-trip exactly, so
+		// emit the IEEE-754 double bit pattern as a hex literal (`0x...`), which
+		// always parses. For `float` we widen the f32 to f64 first — exact, and
+		// LLVM requires the value be representable as float, which it is.
+		number := transmute(f64)value
 		if types.bits(resolved, selected) == 32 {
-			bits := u32(value)
-			number := transmute(f32)bits
-			text = fmt.tprintf("%.9g", number)
-		} else {
-			number := transmute(f64)value
-			text = fmt.tprintf("%.17g", number)
-		}
-		strings.write_string(builder, text)
-		if !strings.contains(text, ".") && !strings.contains(text, "e") && !strings.contains(text, "E") {
-			strings.write_string(builder, ".0")
+			number = f64(transmute(f32)u32(value))
 		}
+		fmt.sbprintf(builder, "0x%016X", transmute(u64)number)
 		return
 	}
 	fmt.sbprintf(builder, "%d", value)
@@ -1198,6 +1198,30 @@ 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_Coerce:
+			if !valid_instruction(instructions, instruction.a) ||
+			   !types.can_coerce_c_integer(instructions[instruction.a].type, instruction.type) {
+				emit_recovery_value(emitter, instruction_index, instruction, "invalid C integer coercion operand")
+				continue
+			}
+			from_type := instructions[instruction.a].type
+			from_bits := types.bits(from_type, emitter.module.target)
+			to_bits := types.bits(instruction.type, emitter.module.target)
+			if from_bits == to_bits {
+				// Same-width signedness change: c_uint and c_int both lower to the
+				// identical `iN`, so this is a pure reinterpret (no-op `select`).
+				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 := "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 .C_Vararg_Promote:
 			if !valid_instruction(instructions, instruction.a) {
 				emit_recovery_value(emitter, instruction_index, instruction, "invalid C variadic promotion operand")

compiler/loader/loader.odin

@@ -149,6 +149,7 @@ translate_c_type :: proc(
 	switch item.kind {
 	case .Invalid:      translated = types.INVALID
 	case .Void:         translated = types.VOID
+	case .C_Bool:       translated = types.BOOL
 	case .C_Char:       translated = types.C_CHAR
 	case .C_Schar:      translated = types.C_SCHAR
 	case .C_Uchar:      translated = types.C_UCHAR

compiler/lower/lower.odin

@@ -490,7 +490,7 @@ lower_expr :: proc(state: ^State, expr_id: hir.Expr_Id) -> ir.Instruction_Id {
 					})
 				}
 				_ = pop(&stack)
-			case .Widen, .C_Vararg_Promote, .Retype, .Weaken_Pointer, .Weaken_Slice, .Decay_Array_Pointer:
+			case .Widen, .C_Coerce, .C_Vararg_Promote, .Retype, .Weaken_Pointer, .Weaken_Slice, .Decay_Array_Pointer:
 				stack[frame_index].stage = 1
 				append(&stack, Lower_Expr_Frame{expr=expr.left})
 			case .Negate:
@@ -547,6 +547,7 @@ lower_expr :: proc(state: ^State, expr_id: hir.Expr_Id) -> ir.Instruction_Id {
 			case .Weaken_Pointer:      op = .Weaken_Pointer
 			case .Weaken_Slice:        op = .Weaken_Slice
 			case .Decay_Array_Pointer: op = .Decay_Array_Pointer
+			case .C_Coerce:            op = .C_Coerce
 			case .C_Vararg_Promote:    op = .C_Vararg_Promote
 			case .Retype:              op = .Retype
 			case:                      op = .Widen

compiler/translatec/translatec.odin

@@ -77,6 +77,7 @@ render_type :: proc(b: ^strings.Builder, result: ^cimport.Result, id: cimport.Ty
 	switch item.kind {
 	case .Invalid:      strings.write_string(b, "void")
 	case .Void:         strings.write_string(b, "void")
+	case .C_Bool:       strings.write_string(b, "bool")
 	case .C_Char:       strings.write_string(b, "c_char")
 	case .C_Schar:      strings.write_string(b, "c_schar")
 	case .C_Uchar:      strings.write_string(b, "c_uchar")
@@ -210,6 +211,13 @@ emit_macros :: proc(b: ^strings.Builder, result: ^cimport.Result, record_names:
 			wrote = true
 			continue
 		}
+		// A macro whose name collides with a brolang keyword (e.g. `true`/`false`
+		// from <stdbool.h>) can't be a binding name; emitting it is a parse error.
+		if lexer.keyword_kind(macro.name) != .Identifier {
+			fmt.sbprintf(b, "# unsupported in bindings: macro '%s' — name is a brolang keyword\n", macro.name)
+			wrote = true
+			continue
+		}
 		if macro.aggregate {
 			emit_aggregate_macro(b, result, macro, record_names)
 			wrote = true

compiler/types/types.odin

@@ -1094,6 +1094,20 @@ can_widen :: proc(from, to: Type) -> bool {
 	       bits(from) < bits(to)
 }
 
+// can_coerce_c_integer reports whether `from` may implicitly convert to `to`
+// under C's integer conversion rules. Brolang keeps its own exact-width scalars
+// strict (`u32 -> i32` is rejected), but C interop types deliberately follow C:
+// virtually every C library relies on it — e.g. an unsigned-backed enum constant
+// (`c_uint`) passed to an `int` (`c_int`) parameter — so disallowing it would
+// make C interop cumbersome. Scope: widening (sext/zext) and same-width
+// signedness changes (no-op reinterpret); narrowing is intentionally excluded so
+// lossy conversions stay an error, matching brolang's trap-on-narrow philosophy.
+can_coerce_c_integer :: proc(from, to: Type) -> bool {
+	return from != to && is_c(from) && is_c(to) &&
+	       is_concrete_integer(from) && is_concrete_integer(to) &&
+	       bits(from) <= bits(to)
+}
+
 widest :: proc(a, b: Type) -> Type {
 	if equal(a, b) && is_concrete_scalar(a) {
 		return a