From 0d7c4d105c7310b09201799bdb0141bc148f3c03 Mon Sep 17 00:00:00 2001
From: Richard Wheeler <Richard_Wheeler@rjew.info>
Date: Tue, 3 Mar 2026 11:20:45 -0500
Subject: [PATCH] cgen: use unsigned int for enum bit fields or unspecified
 size in @[minify] structs (#26678)

* cgen: use unsigned int for enum bit fields of unspecified size in @[minify] structs

In C, the signedness of a bit field declared with an enum type is
implementation-defined. Clang on Windows x64 treats it as signed, so
enum values >= 64 stored in a 7-bit field become negative, corrupting
token kinds, type kinds, operators, etc. TCC and GCC default to
unsigned, masking the bug.

Fix: when emitting a bit-field for an enum field in a @[minify] struct,
use `unsigned int` as the declared type unless the enum has an explicit
unsigned base type (e.g. `as u8`), in which case the typedef is already
unsigned and we keep it to preserve compact layout.

Also add a regression test with a 65-value enum (forces a 7-bit field)
to confirm values >= 64 are not corrupted, and update the existing
minify_option_field must_have file to match the new output.

Fixes #26658

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* ast, token: restore @[minify] on structs removed as workaround for #26658

PR #26661 removed @[minify] from ~50 structs across ast.v, attr.v,
types.v, and token.v as a workaround for enum bit-field signedness
corruption with Clang. PR #26678 fixes the root cause by emitting
`unsigned int` for default-typed enum bit fields, making the workaround
unnecessary. Restore all removed annotations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Richard Wheeler <18647491+PythonWillRule@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 vlib/v/ast/ast.v                              | 45 ++++++++++
 vlib/v/ast/attr.v                             |  1 +
 vlib/v/ast/types.v                            |  7 ++
 vlib/v/gen/c/struct.v                         | 19 +++-
 ...enum_unsigned_not_msvc_windows.c.must_have |  1 +
 .../minify_enum_unsigned_not_msvc_windows.out |  2 +
 .../minify_enum_unsigned_not_msvc_windows.vv  | 86 +++++++++++++++++++
 vlib/v/token/token.v                          |  1 +
 8 files changed, 161 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.out
 create mode 100644 vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.vv

diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 8f5956fb3..a7f1217ab 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -250,6 +250,7 @@ pub:
 	pos token.Pos
 }
 
+@[minify]
 pub struct StringLiteral {
 pub:
 	val      string
@@ -301,6 +302,7 @@ pub enum GenericKindField {
 }
 
 // `foo.bar`
+@[minify]
 pub struct SelectorExpr {
 pub:
 	pos        token.Pos
@@ -351,6 +353,7 @@ pub:
 	pos token.Pos
 }
 
+@[minify]
 pub struct StructField {
 pub:
 	pos              token.Pos
@@ -413,6 +416,7 @@ pub mut:
 }
 
 // const declaration
+@[minify]
 pub struct ConstDecl {
 pub:
 	is_pub bool
@@ -424,6 +428,7 @@ pub mut:
 	is_block     bool         // const() block
 }
 
+@[minify]
 pub struct StructDecl {
 pub:
 	pos           token.Pos
@@ -467,6 +472,7 @@ pub:
 	comments []Comment
 }
 
+@[minify]
 pub struct InterfaceDecl {
 pub:
 	name          string
@@ -510,6 +516,7 @@ pub mut:
 //    ...a
 //    field1: 'hello'
 // }`
+@[minify]
 pub struct StructInit {
 pub:
 	pos             token.Pos
@@ -574,6 +581,7 @@ pub mut:
 }
 
 // function or method declaration
+@[minify]
 pub struct FnDecl {
 pub:
 	name                  string // 'math.bits.normalize'
@@ -667,6 +675,7 @@ pub fn (f &FnDecl) new_method_with_receiver_type(new_type_ Type) FnDecl {
 	}
 }
 
+@[minify]
 pub struct FnTrace {
 pub mut:
 	name string
@@ -678,6 +687,7 @@ pub:
 	is_fn_var   bool
 }
 
+@[minify]
 pub struct Fn {
 pub:
 	is_variadic           bool
@@ -729,6 +739,7 @@ fn (f &Fn) method_equals(o &Fn) bool {
 		&& f.name == o.name
 }
 
+@[minify]
 pub struct Param {
 pub:
 	pos        token.Pos
@@ -794,6 +805,7 @@ fn (p []Param) equals(o []Param) bool {
 }
 
 // break, continue
+@[minify]
 pub struct BranchStmt {
 pub:
 	kind  token.Kind
@@ -869,6 +881,7 @@ pub enum CallKind {
 }
 
 // function or method call expr
+@[minify]
 pub struct CallExpr {
 pub:
 	pos      token.Pos
@@ -926,6 +939,7 @@ pub struct AutofreeArgVar {
 */
 
 // function call argument: `f(callarg)`
+@[minify]
 pub struct CallArg {
 pub:
 	is_mut   bool
@@ -963,6 +977,7 @@ pub enum ComptimeVarKind {
 	aggregate     // aggregate var
 }
 
+@[minify]
 pub struct Var {
 pub:
 	name            string
@@ -1001,6 +1016,7 @@ pub mut:
 
 // used for smartcasting only
 // struct fields change type in scopes
+@[minify]
 pub struct ScopeStructField {
 pub:
 	struct_type Type // type of struct
@@ -1015,6 +1031,7 @@ pub:
 	//        12 <- the current casted type (typ)
 }
 
+@[minify]
 pub struct GlobalField {
 pub:
 	name        string
@@ -1049,6 +1066,7 @@ pub mut:
 	end_comments []Comment
 }
 
+@[minify]
 pub struct EmbeddedFile {
 pub:
 	compression_type string
@@ -1136,6 +1154,7 @@ pub mut:
 
 // TODO: (joe) remove completely, use ident.obj
 // instead which points to the scope object
+@[minify]
 pub struct IdentVar {
 pub mut:
 	typ         Type
@@ -1158,6 +1177,7 @@ pub enum IdentKind {
 }
 
 // A single identifier
+@[minify]
 pub struct Ident {
 pub:
 	language Language
@@ -1219,6 +1239,7 @@ pub fn (i &Ident) var_info() IdentVar {
 
 // left op right
 // See: token.Kind.is_infix
+@[minify]
 pub struct InfixExpr {
 pub:
 	op      token.Kind
@@ -1257,6 +1278,7 @@ pub mut:
 }
 
 // See: token.Kind.is_prefix
+@[minify]
 pub struct PrefixExpr {
 pub:
 	op  token.Kind
@@ -1268,6 +1290,7 @@ pub mut:
 	is_option  bool // IfGuard
 }
 
+@[minify]
 pub struct IndexExpr {
 pub:
 	pos token.Pos
@@ -1286,6 +1309,7 @@ pub mut:
 	typ       Type
 }
 
+@[minify]
 pub struct IfExpr {
 pub:
 	is_comptime   bool
@@ -1333,6 +1357,7 @@ pub mut:
 	scope    &Scope = unsafe { nil }
 }
 
+@[minify]
 pub struct MatchExpr {
 pub:
 	is_comptime bool
@@ -1374,6 +1399,7 @@ pub mut:
 	expected_type Type // for debugging only
 }
 
+@[minify]
 pub struct SelectBranch {
 pub:
 	pos           token.Pos
@@ -1421,6 +1447,7 @@ pub mut:
 	scope &Scope = unsafe { nil }
 }
 
+@[minify]
 pub struct ForInStmt {
 pub:
 	key_var    string
@@ -1482,6 +1509,7 @@ pub mut:
 }
 
 // variable assign statement
+@[minify]
 pub struct AssignStmt {
 pub:
 	op           token.Kind // include: =,:=,+=,-=,*=,/= and so on; for a list of all the assign operators, see vlib/token/token.v
@@ -1538,6 +1566,7 @@ pub mut:
 }
 
 // enum declaration
+@[minify]
 pub struct EnumDecl {
 pub:
 	name             string
@@ -1607,6 +1636,7 @@ pub enum DeferMode {
 // TODO: handle this differently
 // v1 excludes non current os ifdefs so
 // the defer's never get added in the first place
+@[minify]
 pub struct DeferStmt {
 pub:
 	pos   token.Pos
@@ -1628,6 +1658,7 @@ pub mut:
 	comments []Comment
 }
 
+@[minify]
 pub struct GoExpr {
 pub:
 	pos token.Pos
@@ -1636,6 +1667,7 @@ pub mut:
 	is_expr   bool
 }
 
+@[minify]
 pub struct SpawnExpr {
 pub:
 	pos token.Pos
@@ -1658,6 +1690,7 @@ pub:
 	pos  token.Pos
 }
 
+@[minify]
 pub struct ArrayInit {
 pub:
 	pos           token.Pos   // `[]` in []Type{} position
@@ -1705,6 +1738,7 @@ pub mut:
 	elem_type Type
 }
 
+@[minify]
 pub struct MapInit {
 pub:
 	pos       token.Pos
@@ -1724,6 +1758,7 @@ pub mut:
 }
 
 // s[10..20]
+@[minify]
 pub struct RangeExpr {
 pub:
 	has_high bool
@@ -1736,6 +1771,7 @@ pub mut:
 	typ  Type // filled in by checker; the type of `0...1` is `int` for example, while `a`...`z` is `rune` etc
 }
 
+@[minify]
 pub struct CastExpr {
 pub mut:
 	arg       Expr   // `n` in `string(buf, n)`
@@ -1747,6 +1783,7 @@ pub mut:
 	pos       token.Pos
 }
 
+@[minify]
 pub struct AsmStmt {
 pub:
 	arch        pref.Arch
@@ -1764,6 +1801,7 @@ pub mut:
 	local_labels  []string // local to the assembly block
 }
 
+@[minify]
 pub struct AsmTemplate {
 pub mut:
 	name         string
@@ -1951,6 +1989,7 @@ pub:
 }
 
 // `assert a == 0, 'a is zero'`
+@[minify]
 pub struct AssertStmt {
 pub:
 	pos       token.Pos
@@ -2007,6 +2046,7 @@ pub:
 */
 
 // deprecated
+@[minify]
 pub struct Assoc {
 pub:
 	var_name string
@@ -2038,6 +2078,7 @@ pub mut:
 	typ  Type
 }
 
+@[minify]
 pub struct OffsetOf {
 pub:
 	struct_type Type
@@ -2068,6 +2109,7 @@ pub mut:
 	expr Expr
 }
 
+@[minify]
 pub struct TypeOf {
 pub:
 	is_type bool
@@ -2077,6 +2119,7 @@ pub mut:
 	typ  Type
 }
 
+@[minify]
 pub struct DumpExpr {
 pub:
 	pos token.Pos
@@ -2111,6 +2154,7 @@ pub mut:
 	val string
 }
 
+@[minify]
 pub struct ComptimeSelector {
 pub:
 	has_parens bool // if $() is used, for vfmt
@@ -2139,6 +2183,7 @@ pub enum ComptimeCallKind {
 	compile_error
 }
 
+@[minify]
 pub struct ComptimeCall {
 pub:
 	pos         token.Pos
diff --git a/vlib/v/ast/attr.v b/vlib/v/ast/attr.v
index ca8075aa3..445651994 100644
--- a/vlib/v/ast/attr.v
+++ b/vlib/v/ast/attr.v
@@ -14,6 +14,7 @@ pub enum AttrKind {
 }
 
 // e.g. `@[unsafe]`
+@[minify]
 pub struct Attr {
 pub:
 	name    string // [name]
diff --git a/vlib/v/ast/types.v b/vlib/v/ast/types.v
index baf9099b9..f356f9378 100644
--- a/vlib/v/ast/types.v
+++ b/vlib/v/ast/types.v
@@ -106,6 +106,7 @@ pub fn pref_arch_to_table_language(pref_arch pref.Arch) Language {
 // * Table.type_kind(typ) not TypeSymbol.kind.
 // Each TypeSymbol is entered into `Table.type_symbols`.
 // See also: Table.sym.
+@[minify]
 pub struct TypeSymbol {
 pub mut:
 	parent_idx    int
@@ -168,6 +169,7 @@ pub mut:
 	func     Fn
 }
 
+@[minify]
 pub struct Struct {
 pub:
 	attrs       []Attr
@@ -197,6 +199,7 @@ pub mut:
 	concrete_types []Type // concrete types, e.g. [int, string]
 }
 
+@[minify]
 pub struct Interface {
 pub mut:
 	types   []Type // all types that implement this interface
@@ -225,6 +228,7 @@ pub:
 	name_pos         token.Pos
 }
 
+@[minify]
 pub struct Alias {
 pub mut:
 	parent_type Type
@@ -249,6 +253,7 @@ pub mut:
 	elem_type Type
 }
 
+@[minify]
 pub struct ArrayFixed {
 pub:
 	size      int
@@ -276,6 +281,7 @@ pub mut:
 	name_pos   token.Pos
 }
 
+@[minify]
 pub struct SumType {
 pub mut:
 	fields       []StructField
@@ -1730,6 +1736,7 @@ fn (t &Table) shorten_user_defined_typenames(original_name string, import_aliase
 	return '${mod}.${typ}'
 }
 
+@[minify]
 pub struct FnSignatureOpts {
 pub:
 	skip_receiver bool
diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v
index aa809f496..68a367fa1 100644
--- a/vlib/v/gen/c/struct.v
+++ b/vlib/v/gen/c/struct.v
@@ -703,6 +703,7 @@ fn (mut g Gen) struct_decl(s ast.Struct, name string, is_anon bool, is_option bo
 			field_name := c_name(field.name)
 			volatile_prefix := if field.is_volatile { 'volatile ' } else { '' }
 			mut size_suffix := ''
+			mut is_enum_bitfield := false
 			if is_minify && !g.is_cc_msvc && !g.pref.output_cross_c && !field.typ.has_flag(.option)
 				&& !field.typ.has_flag(.result) {
 				if field.typ == ast.bool_type_idx {
@@ -718,6 +719,7 @@ fn (mut g Gen) struct_decl(s ast.Struct, name string, is_anon bool, is_option bo
 								l >>= 1
 							}
 							size_suffix = ' : ${bits_needed}'
+							is_enum_bitfield = true
 						}
 					}
 				}
@@ -734,7 +736,22 @@ fn (mut g Gen) struct_decl(s ast.Struct, name string, is_anon bool, is_option bo
 				}
 			}
 			if !field_is_anon {
-				g.type_definitions.writeln('\t${volatile_prefix}${type_name} ${field_name}${size_suffix};')
+				actual_type := if is_enum_bitfield {
+					enum_info := field_sym.info as ast.Enum
+					if enum_info.typ == ast.int_type {
+						// default enum base type (int): C bit-field signedness is
+						// implementation-defined; force unsigned to avoid Clang treating
+						// it as signed (which corrupts values >= 64 in a 7-bit field, etc.)
+						'unsigned int'
+					} else {
+						// explicit base type (as u8, as i8, as i32, …): the typedef
+						// already carries the correct signedness, so respect the user's choice
+						type_name
+					}
+				} else {
+					type_name
+				}
+				g.type_definitions.writeln('\t${volatile_prefix}${actual_type} ${field_name}${size_suffix};')
 			}
 		}
 	} else {
diff --git a/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.c.must_have b/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.c.must_have
new file mode 100644
index 000000000..0b308aef7
--- /dev/null
+++ b/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.c.must_have
@@ -0,0 +1 @@
+unsigned int kind : 7;
diff --git a/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.out b/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.out
new file mode 100644
index 000000000..c6ce294ea
--- /dev/null
+++ b/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.out
@@ -0,0 +1,2 @@
+true
+64
diff --git a/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.vv b/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.vv
new file mode 100644
index 000000000..814beaed6
--- /dev/null
+++ b/vlib/v/gen/c/testdata/minify_enum_unsigned_not_msvc_windows.vv
@@ -0,0 +1,86 @@
+// Test that enum bit fields in @[minify] structs use unsigned int,
+// so large enum values (>= 64) are not corrupted.
+module main
+
+// 65 values forces bits_needed = 7; value .a64 = 64 would overflow signed 7-bit
+enum LargeEnum {
+	a0
+	a1
+	a2
+	a3
+	a4
+	a5
+	a6
+	a7
+	a8
+	a9
+	a10
+	a11
+	a12
+	a13
+	a14
+	a15
+	a16
+	a17
+	a18
+	a19
+	a20
+	a21
+	a22
+	a23
+	a24
+	a25
+	a26
+	a27
+	a28
+	a29
+	a30
+	a31
+	a32
+	a33
+	a34
+	a35
+	a36
+	a37
+	a38
+	a39
+	a40
+	a41
+	a42
+	a43
+	a44
+	a45
+	a46
+	a47
+	a48
+	a49
+	a50
+	a51
+	a52
+	a53
+	a54
+	a55
+	a56
+	a57
+	a58
+	a59
+	a60
+	a61
+	a62
+	a63
+	a64
+}
+
+@[minify]
+struct Status {
+	kind LargeEnum
+	done bool
+}
+
+fn main() {
+	s := Status{
+		kind: .a64
+	}
+	println(s.kind == .a64)
+	println(int(s.kind))
+}
diff --git a/vlib/v/token/token.v b/vlib/v/token/token.v
index 1020f2d94..a7ae53c8b 100644
--- a/vlib/v/token/token.v
+++ b/vlib/v/token/token.v
@@ -5,6 +5,7 @@ module token
 
 const orm_custom_operators = ['like', 'ilike']
 
+@[minify]
 pub struct Token {
 pub:
 	kind     Kind   // the token number/enum; for quick comparisons
-- 
2.39.5