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* #1735: the values a static-storage initializer holds.
*
* A file-scope or scope variable is initialized before the program runs, so C
* requires each value in its initializer to be a constant expression (C99
* 6.7.8p4): a `const` object is not one, and neither is ADR-044's clamp helper
* call. Each is a value fixed at compile time (ADR-044, #1175), `mut` or not.
* One of a cnx number or bool type that is not written as a literal is
* folded here, at the type its position holds it at: the one answer 2.1
* rejects (E0909, E0910) and 2.2 spells. One of any other type (an enum, a
* struct) has no typed fold, but is asked the same question untyped, so one
* that reads a variable or calls a function is rejected too (#2018).
*/
import type IProgram from "../../../types/IProgram";
import type TValueBinding from "../../../types/TValueBinding";
import type ISourcePosition from "../../../utils/types/ISourcePosition";
import type IVariableSymbol from "../../../types/symbols/IVariableSymbol";
import type IValuePosition from "../../../types/IValuePosition";
import type TConstExpr from "../../../types/TConstExpr";
import type TSettledConst from "../../../types/TSettledConst";
import type IProgramSyntax from "../../../types/syntax/IProgramSyntax";
import type TMemberDeclaration from "../../../types/syntax/TMemberDeclaration";
import type TExpression from "../../../types/syntax/TExpression";
import ConstExprLowering from "../../../utils/ConstExprLowering";
import ConstExprPrinter from "../../../utils/ConstExprPrinter";
import ConstantEvaluator from "../../../utils/ConstantEvaluator";
import type IConstantEnvironment from "../../../utils/types/IConstantEnvironment";
import ConstantFold from "../../../utils/ConstantFold";
import LengthProperty from "../../../utils/LengthProperty";
import TypeCheckUtils from "../../../utils/TypeCheckUtils";
import TypeText from "../../../utils/TypeText";
import type IStaticValue from "../types/IStaticValue";
import ValuePositions from "./ValuePositions";
type TConstName = Extract<TConstExpr, { kind: "name" }>;
const WRAPPING_OPERATORS: ReadonlySet<string> = new Set(["+", "-", "*", "<<"]);
type TReason = Extract<TSettledConst, { kind: "notConstant" }>["reason"];
/** What a value of no number or bool type has no value for C by */
const UNTYPED_WITHOUT_VALUE: ReadonlySet<TReason> = new Set<TReason>([
"variable",
"parameter",
"call",
]);
class StaticInitializers {
/** Each value to fold in the file's static-storage initializers */
static values(
program: IProgramSyntax,
positions: ReadonlyMap<TExpression, IValuePosition>,
): IStaticValue[] {
return program.members
.flatMap(({ declaration }) =>
StaticInitializers.declarations(declaration),
)
.flatMap((declaration) =>
StaticInitializers.leaves(declaration.initializer!).flatMap((value) => {
return StaticInitializers.isLiteral(value)
? []
: [
{
declaration,
value,
typeName: StaticInitializers.typeAt(positions, value),
},
];
}),
);
}
/**
* The value, held at its type, by the fold every pass shares. One of no
* number or bool type is only asked whether it has a value: null when it
* does, why not when it does not. A header macro is left to C, as it is
* written (#1127).
*/
static settle(
value: IStaticValue,
program: IProgram,
sourceFile: string,
): TSettledConst | null {
return StaticInitializers.settleIn(
value,
ConstantFold.environment(program, sourceFile),
);
}
/**
* `settle`, reading each header macro cnx can: what 2.1 checks, so a
* macro's arithmetic clamps or wraps no more silently than a const's
* (#1735 review 2). C is still given the macro.
*/
static check(
value: IStaticValue,
program: IProgram,
sourceFile: string,
): TSettledConst | null {
return StaticInitializers.settleIn(
value,
ConstantFold.readingHeaderMacros(program, sourceFile),
);
}
private static settleIn(
value: IStaticValue,
env: IConstantEnvironment,
): TSettledConst | null {
const lowered = ConstExprLowering.lower(value.value);
if (value.typeName !== null) {
const settled = ConstantFold.primitiveValue(lowered, env, value.typeName);
// A float fold past its type's range is infinite, which C has no
// constant for (#1735 review 2)
return settled?.kind === "float" &&
!Number.isFinite(Number(settled.digits))
? { kind: "overflow", typeName: settled.typeName }
: settled;
}
const result = ConstantEvaluator.evaluate(lowered, env);
return result.kind === "value" ? null : result;
}
/**
* Whether the value has none C can be given, which 2.1 reports (E0909):
* one of a number or bool type that cnx cannot fold and C cannot
* evaluate; one of any other type that reads a variable or calls a function
*/
static lacksValue(value: IStaticValue, settled: TSettledConst): boolean {
Iif (settled.kind !== "notConstant") return false;
return value.typeName === null
? UNTYPED_WITHOUT_VALUE.has(settled.reason)
: !StaticInitializers.cHasValue(settled);
}
/**
* A value C evaluates that reads a cnx const, written as dimensions are
* (`ConstantFold.settled`): each cnx name as its value, each header name
* as C spells it -- since C cannot read the const object (#1735 review)
*/
static cText(
value: IStaticValue,
program: IProgram,
sourceFile: string,
): string {
return ConstExprPrinter.toC(
ConstExprLowering.lower(value.value),
ConstantFold.environment(program, sourceFile),
);
}
/**
* Whether the value does arithmetic that can clamp or wrap: what cnx
* must see every operand of to check (#1735 review 2)
*/
static wraps(value: IStaticValue): boolean {
const wraps = (expr: TConstExpr): boolean => {
switch (expr.kind) {
case "binary":
return (
WRAPPING_OPERATORS.has(expr.op) ||
wraps(expr.left) ||
wraps(expr.right)
);
case "unary":
return expr.op === "-" || wraps(expr.operand);
case "cast":
return wraps(expr.operand);
case "ternary":
return (
wraps(expr.condition) ||
wraps(expr.whenTrue) ||
wraps(expr.whenFalse)
);
default:
return false;
}
};
return wraps(ConstExprLowering.lower(value.value));
}
/** The value's outermost form, which says what does not fit */
static formOf(value: IStaticValue): TConstExpr["kind"] {
return ConstExprLowering.lower(value.value).kind;
}
/**
* Whether the value reads a variable, `const` or not: what C rejects in a
* static initializer, where an enum member or a length property is not
*/
static readsVariable(
value: TExpression,
program: IProgram,
sourceFile: string,
): boolean {
return StaticInitializers.bindings(value, program, sourceFile).some(
({ binding }) => binding.kind === "variable" || binding.kind === "local",
);
}
/**
* What each name the value reads binds to, and where it is written; a
* length property's subject is a size, which C is never asked to read
*/
static bindings(
value: TExpression,
program: IProgram,
sourceFile: string,
): { readonly binding: TValueBinding; readonly at: ISourcePosition }[] {
return StaticInitializers.names(ConstExprLowering.lower(value)).flatMap(
(name) => {
if (LengthProperty.isLength(name.path.at(-1) ?? "")) return [];
const target = program.constantTargetOf(sourceFile, name);
return target === null
? []
: [{ binding: target.binding, at: name.at }];
},
);
}
/**
* Whether C has a value cnx does not: a char literal, or a name only a
* header declares, reached directly or through the consts it is read from
*/
static cHasValue(settled: TSettledConst): boolean {
Iif (settled.kind === "foreign") return true;
if (settled.kind !== "notConstant") return false;
if (settled.reason === "character") return true;
return settled.reason === "unfolded" && settled.because !== undefined
? StaticInitializers.cHasValue(settled.because)
: false;
}
/**
* The const a value names alone, as `CH` or `S.LIMIT` -- what C is given
* when cnx has no value for it but C does (`cHasValue`) -- or null
*/
static namedConst(
value: TExpression,
program: IProgram,
sourceFile: string,
): IVariableSymbol | null {
const lowered = ConstExprLowering.lower(value);
if (lowered.kind !== "name") return null;
const target = program.constantTargetOf(sourceFile, lowered);
return target?.binding.kind === "variable" && target.rest.length === 0
? target.binding.symbol
: null;
}
/** Each bare name the value reads (`N`, not `this.N` or `S.N`) */
static bareNames(value: TExpression): TConstName[] {
return StaticInitializers.names(ConstExprLowering.lower(value)).filter(
(name) => name.root === null && name.path.length === 1,
);
}
private static names(expr: TConstExpr): TConstName[] {
switch (expr.kind) {
case "name":
return [expr];
case "cast":
case "unary":
return StaticInitializers.names(expr.operand);
case "binary":
return [
...StaticInitializers.names(expr.left),
...StaticInitializers.names(expr.right),
];
case "ternary":
return [expr.condition, expr.whenTrue, expr.whenFalse].flatMap(
StaticInitializers.names,
);
default:
return [];
}
}
/** The file's file-scope and scope variables that have an initializer */
private static declarations(
declaration: TMemberDeclaration,
): IStaticValue["declaration"][] {
return declaration.kind === "variableDeclaration" && declaration.initializer
? [declaration]
: [];
}
/** The values an initializer holds: an array's elements, a struct's fields */
private static leaves(expr: TExpression): TExpression[] {
switch (expr.kind) {
case "arrayInitializer":
return expr.fill === null
? expr.elements.flatMap(StaticInitializers.leaves)
: StaticInitializers.leaves(expr.fill);
case "structInitializer":
return expr.fields.flatMap((field) =>
StaticInitializers.leaves(field.value),
);
default:
return [expr];
}
}
/** The number or bool type the value's position holds it at, or null */
private static typeAt(
positions: ReadonlyMap<TExpression, IValuePosition>,
value: TExpression,
): string | null {
const typeText = ValuePositions.at(positions, value).typeText;
Iif (typeText === null) return null;
const typeName = TypeText.withoutDimensions(typeText);
return TypeCheckUtils.isInteger(typeName) ||
TypeCheckUtils.isFloat(typeName) ||
typeName === "bool"
? typeName
: null;
}
/** A literal is written as it stands, so it keeps its notation (`0xAB`) */
private static isLiteral(value: TExpression): boolean {
return (
value.kind === "literal" ||
(value.kind === "unary" &&
value.operator === "-" &&
value.operand.kind === "literal")
);
}
}
export default StaticInitializers;
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