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Sema: forbid packed unions with mismatched field bit sizes

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This commit is contained in:
Andrew Kelley 2025-09-05 18:45:24 -07:00
parent 1d764c1fdf
commit 52c6d7a929
1 changed files with 55 additions and 21 deletions
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76
src/Sema.zig
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@ -35614,6 +35614,12 @@ fn unionFields(
if (small.any_aligned_fields)
try field_aligns.ensureTotalCapacityPrecise(sema.arena, fields_len);
var max_bits: u64 = 0;
var min_bits: u64 = std.math.maxInt(u64);
var max_bits_src: LazySrcLoc = undefined;
var min_bits_src: LazySrcLoc = undefined;
var max_bits_ty: Type = undefined;
var min_bits_ty: Type = undefined;
const bits_per_field = 4;
const fields_per_u32 = 32 / bits_per_field;
const bit_bags_count = std.math.divCeil(usize, fields_len, fields_per_u32) catch unreachable;
@ -35622,6 +35628,7 @@ fn unionFields(
var cur_bit_bag: u32 = undefined;
var field_i: u32 = 0;
var last_tag_val: ?Value = null;
const layout = union_type.flagsUnordered(ip).layout;
while (field_i < fields_len) : (field_i += 1) {
if (field_i % fields_per_u32 == 0) {
cur_bit_bag = zir.extra[bit_bag_index];
@ -35773,31 +35780,45 @@ fn unionFields(
};
return sema.failWithOwnedErrorMsg(&block_scope, msg);
}
const layout = union_type.flagsUnordered(ip).layout;
if (layout == .@"extern" and
!try sema.validateExternType(field_ty, .union_field))
{
const msg = msg: {
const msg = try sema.errMsg(type_src, "extern unions cannot contain fields of type '{f}'", .{field_ty.fmt(pt)});
errdefer msg.destroy(sema.gpa);
switch (layout) {
.@"extern" => if (!try sema.validateExternType(field_ty, .union_field)) {
const msg = msg: {
const msg = try sema.errMsg(type_src, "extern unions cannot contain fields of type '{f}'", .{field_ty.fmt(pt)});
errdefer msg.destroy(sema.gpa);
try sema.explainWhyTypeIsNotExtern(msg, type_src, field_ty, .union_field);
try sema.explainWhyTypeIsNotExtern(msg, type_src, field_ty, .union_field);
try sema.addDeclaredHereNote(msg, field_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(&block_scope, msg);
} else if (layout == .@"packed" and !try sema.validatePackedType(field_ty)) {
const msg = msg: {
const msg = try sema.errMsg(type_src, "packed unions cannot contain fields of type '{f}'", .{field_ty.fmt(pt)});
errdefer msg.destroy(sema.gpa);
try sema.addDeclaredHereNote(msg, field_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(&block_scope, msg);
},
.@"packed" => {
if (!try sema.validatePackedType(field_ty)) {
const msg = msg: {
const msg = try sema.errMsg(type_src, "packed unions cannot contain fields of type '{f}'", .{field_ty.fmt(pt)});
errdefer msg.destroy(sema.gpa);
try sema.explainWhyTypeIsNotPacked(msg, type_src, field_ty);
try sema.explainWhyTypeIsNotPacked(msg, type_src, field_ty);
try sema.addDeclaredHereNote(msg, field_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(&block_scope, msg);
try sema.addDeclaredHereNote(msg, field_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(&block_scope, msg);
}
const field_bits = try field_ty.bitSizeSema(pt);
if (field_bits >= max_bits) {
max_bits = field_bits;
max_bits_src = type_src;
max_bits_ty = field_ty;
}
if (field_bits <= min_bits) {
min_bits = field_bits;
min_bits_src = type_src;
min_bits_ty = field_ty;
}
},
.auto => {},
}
field_types.appendAssumeCapacity(field_ty.toIntern());
@ -35815,6 +35836,19 @@ fn unionFields(
union_type.setFieldTypes(ip, field_types.items);
union_type.setFieldAligns(ip, field_aligns.items);
if (layout == .@"packed" and fields_len != 0 and min_bits != max_bits) {
const msg = msg: {
const msg = try sema.errMsg(src, "packed union has fields with mismatching bit sizes", .{});
errdefer msg.destroy(sema.gpa);
try sema.errNote(min_bits_src, msg, "{d} bits here", .{min_bits});
try sema.addDeclaredHereNote(msg, min_bits_ty);
try sema.errNote(max_bits_src, msg, "{d} bits here", .{max_bits});
try sema.addDeclaredHereNote(msg, max_bits_ty);
break :msg msg;
};
return sema.failWithOwnedErrorMsg(&block_scope, msg);
}
if (explicit_tags_seen.len > 0) {
const tag_ty = union_type.tagTypeUnordered(ip);
const tag_info = ip.loadEnumType(tag_ty);