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Signed types for enum tags #2459

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merged 5 commits into from
May 12, 2019
Merged

Signed types for enum tags #2459

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917bd41
Validate enum tag for extern enum
LemonBoy May 9, 2019
c766f3f
Support signed types as enum tags
LemonBoy May 9, 2019
655794f
amend type_is_valid_extern_enum_tag
LemonBoy May 10, 2019
b05e8d4
Change the enum value allocation strategy
LemonBoy May 10, 2019
d210628
Amend the error messages
LemonBoy May 11, 2019
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108 changes: 61 additions & 47 deletions src/analyze.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1908,6 +1908,18 @@ static Error resolve_union_type(CodeGen *g, ZigType *union_type) {
return ErrorNone;
}

static bool type_is_valid_extern_enum_tag(CodeGen *g, ZigType *ty) {
// Only integer types are allowed by the C ABI
if(ty->id != ZigTypeIdInt)
return false;

// According to the ANSI C standard the enumeration type should be either a
// signed char, a signed integer or an unsigned one. But GCC/Clang allow
// other integral types as a compiler extension so let's accomodate them
// aswell.
return type_allowed_in_extern(g, ty);
}

static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
assert(enum_type->id == ZigTypeIdEnum);

Expand Down Expand Up @@ -1965,7 +1977,6 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
enum_type->abi_size = tag_int_type->abi_size;
enum_type->abi_align = tag_int_type->abi_align;

// TODO: Are extern enums allowed to have an init_arg_expr?
if (decl_node->data.container_decl.init_arg_expr != nullptr) {
ZigType *wanted_tag_int_type = analyze_type_expr(g, scope, decl_node->data.container_decl.init_arg_expr);
if (type_is_invalid(wanted_tag_int_type)) {
Expand All @@ -1974,24 +1985,29 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
enum_type->data.enumeration.is_invalid = true;
add_node_error(g, decl_node->data.container_decl.init_arg_expr,
buf_sprintf("expected integer, found '%s'", buf_ptr(&wanted_tag_int_type->name)));
} else if (wanted_tag_int_type->data.integral.is_signed) {
} else if (enum_type->data.enumeration.layout == ContainerLayoutExtern &&
!type_is_valid_extern_enum_tag(g, wanted_tag_int_type)) {
enum_type->data.enumeration.is_invalid = true;
add_node_error(g, decl_node->data.container_decl.init_arg_expr,
buf_sprintf("expected unsigned integer, found '%s'", buf_ptr(&wanted_tag_int_type->name)));
} else if (wanted_tag_int_type->data.integral.bit_count < tag_int_type->data.integral.bit_count) {
enum_type->data.enumeration.is_invalid = true;
add_node_error(g, decl_node->data.container_decl.init_arg_expr,
buf_sprintf("'%s' too small to hold all bits; must be at least '%s'",
buf_ptr(&wanted_tag_int_type->name), buf_ptr(&tag_int_type->name)));
ErrorMsg *msg = add_node_error(g, decl_node->data.container_decl.init_arg_expr,
buf_sprintf("'%s' is not a valid tag type for an extern enum",
buf_ptr(&wanted_tag_int_type->name)));
add_error_note(g, msg, decl_node->data.container_decl.init_arg_expr,
buf_sprintf("any integral type of size 8, 16, 32, 64 or 128 bit is valid"));
} else {
tag_int_type = wanted_tag_int_type;
}
}

enum_type->data.enumeration.tag_int_type = tag_int_type;
enum_type->size_in_bits = tag_int_type->size_in_bits;
enum_type->abi_size = tag_int_type->abi_size;
enum_type->abi_align = tag_int_type->abi_align;

BigInt bi_one;
bigint_init_unsigned(&bi_one, 1);

TypeEnumField *last_enum_field = nullptr;

for (uint32_t field_i = 0; field_i < field_count; field_i += 1) {
AstNode *field_node = decl_node->data.container_decl.fields.at(field_i);
TypeEnumField *type_enum_field = &enum_type->data.enumeration.fields[field_i];
Expand All @@ -2017,60 +2033,58 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {

AstNode *tag_value = field_node->data.struct_field.value;

// In this first pass we resolve explicit tag values.
// In a second pass we will fill in the unspecified ones.
if (tag_value != nullptr) {
// A user-specified value is available
ConstExprValue *result = analyze_const_value(g, scope, tag_value, tag_int_type, nullptr);
if (type_is_invalid(result->type)) {
enum_type->data.enumeration.is_invalid = true;
continue;
}

assert(result->special != ConstValSpecialRuntime);
assert(result->type->id == ZigTypeIdInt ||
result->type->id == ZigTypeIdComptimeInt);
auto entry = occupied_tag_values.put_unique(result->data.x_bigint, tag_value);
if (entry == nullptr) {
bigint_init_bigint(&type_enum_field->value, &result->data.x_bigint);
assert(result->type->id == ZigTypeIdInt || result->type->id == ZigTypeIdComptimeInt);

bigint_init_bigint(&type_enum_field->value, &result->data.x_bigint);
} else {
// No value was explicitly specified: allocate the last value + 1
// or, if this is the first element, zero
if (last_enum_field != nullptr) {
bigint_add(&type_enum_field->value, &last_enum_field->value, &bi_one);
} else {
Buf *val_buf = buf_alloc();
bigint_append_buf(val_buf, &result->data.x_bigint, 10);
bigint_init_unsigned(&type_enum_field->value, 0);
}

ErrorMsg *msg = add_node_error(g, tag_value,
buf_sprintf("enum tag value %s already taken", buf_ptr(val_buf)));
add_error_note(g, msg, entry->value,
buf_sprintf("other occurrence here"));
// Make sure we can represent this number with tag_int_type
if (!bigint_fits_in_bits(&type_enum_field->value,
tag_int_type->size_in_bits,
tag_int_type->data.integral.is_signed)) {
enum_type->data.enumeration.is_invalid = true;
continue;

Buf *val_buf = buf_alloc();
bigint_append_buf(val_buf, &type_enum_field->value, 10);
add_node_error(g, field_node,
buf_sprintf("enumeration value %s too large for type '%s'",
buf_ptr(val_buf), buf_ptr(&tag_int_type->name)));

break;
}
}
}

// Now iterate again and populate the unspecified tag values
uint32_t next_maybe_unoccupied_index = 0;
// Make sure the value is unique
auto entry = occupied_tag_values.put_unique(type_enum_field->value, field_node);
if (entry != nullptr) {
enum_type->data.enumeration.is_invalid = true;

for (uint32_t field_i = 0; field_i < field_count; field_i += 1) {
AstNode *field_node = decl_node->data.container_decl.fields.at(field_i);
TypeEnumField *type_enum_field = &enum_type->data.enumeration.fields[field_i];
AstNode *tag_value = field_node->data.struct_field.value;
Buf *val_buf = buf_alloc();
bigint_append_buf(val_buf, &type_enum_field->value, 10);

if (tag_value == nullptr) {
if (occupied_tag_values.size() == 0) {
bigint_init_unsigned(&type_enum_field->value, next_maybe_unoccupied_index);
next_maybe_unoccupied_index += 1;
} else {
BigInt proposed_value;
for (;;) {
bigint_init_unsigned(&proposed_value, next_maybe_unoccupied_index);
next_maybe_unoccupied_index += 1;
auto entry = occupied_tag_values.put_unique(proposed_value, field_node);
if (entry != nullptr) {
continue;
}
break;
}
bigint_init_bigint(&type_enum_field->value, &proposed_value);
}
ErrorMsg *msg = add_node_error(g, field_node,
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If you make this field_node->data.struct_field.value then the compile error test won't need updated, right? It seems better to point at the value than the field. Likewise with entry->value->data.struct_field.value.

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field_node->data.struct_field.value is null if the user didn't specify it, I've made it point to the field declaration because that's always present.

I can make it choose either of them based on whether value is null or not but I'm not very fond of this "asymmetry" in the error messages.

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Ahh, that makes sense!

buf_sprintf("enum tag value %s already taken", buf_ptr(val_buf)));
add_error_note(g, msg, entry->value,
buf_sprintf("other occurrence here"));
}

last_enum_field = type_enum_field;
}

enum_type->data.enumeration.zero_bits_loop_flag = false;
Expand Down
40 changes: 17 additions & 23 deletions test/compile_errors.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,19 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
"tmp.zig:3:32: error: cast discards const qualifier",
);

cases.add(
"overflow in enum value allocation",
\\const Moo = enum(u8) {
\\ Last = 255,
\\ Over,
\\};
\\pub fn main() void {
\\ var y = Moo.Last;
\\}
,
"tmp.zig:3:5: error: enumeration value 256 too large for type 'u8'",
);

cases.add(
"attempt to cast enum literal to error",
\\export fn entry() void {
Expand Down Expand Up @@ -5383,8 +5396,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
"tmp.zig:12:20: note: referenced here",
);

cases.add(
"specify enum tag type that is too small",
cases.add("specify enum tag type that is too small",
\\const Small = enum (u2) {
\\ One,
\\ Two,
Expand All @@ -5396,9 +5408,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
\\export fn entry() void {
\\ var x = Small.One;
\\}
,
"tmp.zig:1:21: error: 'u2' too small to hold all bits; must be at least 'u3'",
);
, "tmp.zig:6:5: error: enumeration value 4 too large for type 'u2'");

cases.add(
"specify non-integer enum tag type",
Expand Down Expand Up @@ -5448,22 +5458,6 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
"tmp.zig:10:31: error: expected type 'u2', found 'u3'",
);

cases.add(
"non unsigned integer enum tag type",
\\const Small = enum(i2) {
\\ One,
\\ Two,
\\ Three,
\\ Four,
\\};
\\
\\export fn entry() void {
\\ var y = Small.Two;
\\}
,
"tmp.zig:1:20: error: expected unsigned integer, found 'i2'",
);

cases.add(
"struct fields with value assignments",
\\const MultipleChoice = struct {
Expand Down Expand Up @@ -5522,8 +5516,8 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
\\ var x = MultipleChoice.C;
\\}
,
"tmp.zig:6:9: error: enum tag value 60 already taken",
"tmp.zig:4:9: note: other occurrence here",
"tmp.zig:6:5: error: enum tag value 60 already taken",
"tmp.zig:4:5: note: other occurrence here",
);

cases.add(
Expand Down
24 changes: 24 additions & 0 deletions test/stage1/behavior/enum.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -938,3 +938,27 @@ test "enum literal in array literal" {
expect(array[0] == .one);
expect(array[1] == .two);
}

test "signed integer as enum tag" {
const SignedEnum = enum(i2) {
A0 = -1,
A1 = 0,
A2 = 1,
};

expect(@enumToInt(SignedEnum.A0) == -1);
expect(@enumToInt(SignedEnum.A1) == 0);
expect(@enumToInt(SignedEnum.A2) == 1);
}

test "enum value allocation" {
const LargeEnum = enum(u32) {
A0 = 0x80000000,
A1,
A2,
};

expect(@enumToInt(LargeEnum.A0) == 0x80000000);
expect(@enumToInt(LargeEnum.A1) == 0x80000001);
expect(@enumToInt(LargeEnum.A2) == 0x80000002);
}