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* Shift Analyzer: E0805 (signed operand) and E0873 (amount out of range).
*
* MISRA C:2012 Rule 10.1: Operands shall not be of an inappropriate essential type
* - Left-shifting negative signed values is undefined behavior in C
* - Right-shifting negative signed values is implementation-defined in C
*
* C-Next rejects all shift operations on signed types (i8, i16, i32, i64) at
* compile time to ensure defined, portable behavior.
*
* MISRA C:2012 Rule 12.2: the right operand of a shift shall lie in the range
* zero to one less than the essential width of the left operand. #1322 moved
* that rule here from `output/`. It reads the LEADING operand's type, as
* codegen did (`(a + 1) << 9` is a composite and stays untyped), and
* evaluates the amount when it is a literal or a named const. The compound
* forms (`a <<<- 9`) are checked the same way.
*
* The signed rule asks whether ANY value leaf of the shifted operand is
* signed, or is a negated literal (`-5`, signed in C, though an unsuffixed
* literal has no category of its own under ADR-052). The width rule asks the
* leading operand's type.
*
* Every operand is typed by the one operand typer, and every amount is
* evaluated by it, binding names through Program's lexical frames (#1668):
* a field, element, cast, call or C header operand is typed like a variable,
* and a const local shadows as it does everywhere else. Every assignment
* site is checked, `for` headers included (#1726).
*/
import { ParseTreeWalker, ParserRuleContext } from "antlr4ng";
import * as Parser from "../../PARSE/2-Parse/grammar/CNextParser";
import IShiftError from "./types/IShiftError";
import ParserUtils from "../../utils/ParserUtils";
import OperandTyper from "../../utils/OperandTyper";
import TypeCheckUtils from "../../utils/TypeCheckUtils";
import BinaryOperatorLevelListener from "./BinaryOperatorLevelListener";
import AssignmentSiteListener from "./AssignmentSiteListener";
import type IAnalysisContext from "./types/IAnalysisContext";
import type TAssignmentSite from "./types/TAssignmentSite";
import type IOperandType from "../../types/IOperandType";
class ShiftCheck {
constructor(
private readonly analyzer: ShiftAnalyzer,
private readonly context: IAnalysisContext,
) {}
/** Each `<<` / `>>` of one shift level, between adjacent operands */
public checkLevel(operands: ParserRuleContext[]): void {
const parent = operands[0]?.parent;
Iif (!parent) return;
for (let i = 0; i < operands.length - 1; i += 1) {
const operator = parent.getChild(i * 2 + 1)?.getText() ?? "";
Iif (operator !== "<<" && operator !== ">>") continue;
const left = operands[i];
if (this.isSigned(left)) {
const { line, column } = ParserUtils.getPosition(left);
this.analyzer.addError(line, column, operator);
continue;
}
// Rule 12.2: the amount against the width of the value shifted. For a
// composite that is ADR-044's composite type, the one codegen emits it
// by (#1668 review: this read the first leaf's, so `a + b << 9` with a
// u8 `a` and a u32 `b` was E0873 against 8 bits, while the C shifts
// `cnx_clamp_add_u32(a, b)`)
this.checkAmount(
ShiftCheck.shiftedType(left, this.context),
operands[i + 1],
parent,
);
}
}
/**
* `<<<-` and `>><-`: a signed target is E0805 (#1008), and the amount is
* checked against the target's width, which codegen never did -- `a <<<- 9`
* on a u8 emitted `a = (uint8_t)(a << 9U)` at exit 0.
*/
public checkAssignment(site: TAssignmentSite): void {
const operator = site.assignmentOperator();
const left = operator.LSHIFT_ASSIGN() !== null;
if (!left && operator.RSHIFT_ASSIGN() === null) return;
const target = site.assignmentTarget();
const targetType = OperandTyper.typeOfTarget(target, this.context);
if (targetType?.category === "signed") {
const { line, column } = ParserUtils.getPosition(target);
this.analyzer.addError(line, column, left ? "<<<-" : ">><-");
return;
}
this.checkAmount(targetType, site.expression(), site);
}
/**
* The type of the value a shift shifts: a composite's integer type, as the
* typer settled it, or the operand's own type.
*/
private static shiftedType(
left: ParserRuleContext,
context: IAnalysisContext,
): IOperandType | null {
const t = OperandTyper.typeOf(left, context);
if (t?.form.kind !== "composite") return t;
Iif (t.typeName === null || t.bitWidth === null) return null;
return {
...t,
category: TypeCheckUtils.isSigned(t.typeName) ? "signed" : "unsigned",
};
}
/** Any value leaf signed, or a negated literal */
private isSigned(operand: ParserRuleContext): boolean {
return OperandTyper.valueLeaves(operand, this.context).some(
(leaf) =>
leaf !== null &&
(leaf.category === "signed" ||
(leaf.form.kind === "literal" && leaf.form.negated)),
);
}
/**
* E0873: a compile-time shift amount that is negative or not below the
* width of the shifted operand's type. Silent when either side is unknown
* -- a runtime amount, or an operand with no integer width. A bit of a
* scalar is not an integer operand of its own (ADR-024).
*/
private checkAmount(
shifted: IOperandType | null,
amountExpr: ParserRuleContext,
at: ParserRuleContext,
): void {
Iif (shifted === null) return;
Iif (shifted.form.kind === "bitIndex" || shifted.form.kind === "bitRange") {
return;
}
const integer =
shifted.category === "signed" || shifted.category === "unsigned";
const width = shifted.bitWidth;
if (!integer || width === null || shifted.dimensions.length > 0) return;
const leftType = shifted.typeName ?? shifted.category;
const amount = OperandTyper.constantOf(amountExpr, this.context);
if (amount === null) return;
const { line, column } = ParserUtils.getPosition(amountExpr);
if (amount < 0) {
this.analyzer.addAmountError(
line,
column,
`Negative shift amount (${amount}) is undefined behavior (type: ${leftType}, expression: ${at.getText()})`,
"Shift amounts must be non-negative (MISRA C:2012 Rule 12.2).",
);
return;
}
if (amount >= width) {
this.analyzer.addAmountError(
line,
column,
`Shift amount (${amount}) exceeds type width (${width} bits) for type '${leftType}' (expression: ${at.getText()})`,
`Shift amount must be < ${width} for ${width}-bit types; shifting by the width or more is undefined behavior (MISRA C:2012 Rule 12.2).`,
);
}
}
}
/**
* Analyzer that detects shift operations on signed integer types, and shift
* amounts outside the shifted operand's width.
*/
class ShiftAnalyzer {
private errors: IShiftError[] = [];
/** #1456: handed in rather than read off shared state. */
// eslint-disable-next-line @typescript-eslint/lines-between-class-members
constructor(private readonly context: IAnalysisContext) {}
/**
* Analyze the parse tree for shift operations
*/
public analyze(tree: Parser.ProgramContext): IShiftError[] {
this.errors = [];
const check = new ShiftCheck(this, this.context);
ParseTreeWalker.DEFAULT.walk(
new BinaryOperatorLevelListener((operands, level) => {
if (level === "shift") check.checkLevel(operands);
}),
tree,
);
ParseTreeWalker.DEFAULT.walk(
new AssignmentSiteListener((site) => check.checkAssignment(site)),
tree,
);
// Two walks; report in source order, as the one walk they replace did
return this.errors.sort((a, b) => a.line - b.line || a.column - b.column);
}
/**
* Add a signed shift error
*/
public addError(line: number, column: number, operator: string): void {
this.errors.push({
code: "E0805",
line,
column,
message: `Shift operator '${operator}' not allowed on signed integer types`,
helpText:
"Shift operations on signed integers have undefined (<<) or implementation-defined (>>) behavior. Use unsigned types (u8, u16, u32, u64) for bit manipulation.",
});
}
/**
* Add a shift amount error (E0873)
*/
public addAmountError(
line: number,
column: number,
message: string,
helpText: string,
): void {
this.errors.push({ code: "E0873", line, column, message, helpText });
}
}
export default ShiftAnalyzer;
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