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* Null Check Analyzer
* Enforces NULL safety for C library interop (ADR-046)
*
* C-Next eliminates null bugs by design. This analyzer provides a controlled
* exception for C interop: Variables storing nullable C pointer returns must
* use the c_ prefix to indicate they hold C interop values.
*
* Rules:
* - C functions returning nullable pointers require c_ prefix for storage
* - NULL keyword only valid in equality comparison context (= or !=)
* - Dynamic allocation functions (malloc, etc.) remain forbidden (ADR-003)
*/
import { ParseTreeWalker } from "antlr4ng";
import { CNextListener } from "../parser/grammar/CNextListener";
import * as Parser from "../parser/grammar/CNextParser";
import INullCheckError from "./types/INullCheckError";
import ParserUtils from "../../../utils/ParserUtils";
/**
* Metadata for C library functions that can return NULL
*/
interface ICLibraryFunction {
header: string;
nullMeaning: string;
docsUrl: string;
}
/**
* C library functions that return nullable pointers
* These require the c_ prefix when stored in variables (ADR-046)
*/
const NULLABLE_C_FUNCTIONS: Map<string, ICLibraryFunction> = new Map([
// Stream I/O
[
"fgets",
{
header: "stdio.h",
nullMeaning: "EOF or error",
docsUrl: "https://en.cppreference.com/w/c/io/fgets",
},
],
[
"fputs",
{
header: "stdio.h",
nullMeaning: "Write error (EOF)",
docsUrl: "https://en.cppreference.com/w/c/io/fputs",
},
],
[
"fgetc",
{
header: "stdio.h",
nullMeaning: "EOF or error",
docsUrl: "https://en.cppreference.com/w/c/io/fgetc",
},
],
[
"fputc",
{
header: "stdio.h",
nullMeaning: "Write error (EOF)",
docsUrl: "https://en.cppreference.com/w/c/io/fputc",
},
],
[
"gets",
{
header: "stdio.h",
nullMeaning: "EOF or error (DEPRECATED)",
docsUrl: "https://en.cppreference.com/w/c/io/gets",
},
],
// File handling (now allowed with c_ prefix)
[
"fopen",
{
header: "stdio.h",
nullMeaning: "Failed to open file",
docsUrl: "https://en.cppreference.com/w/c/io/fopen",
},
],
[
"freopen",
{
header: "stdio.h",
nullMeaning: "Failed to reopen",
docsUrl: "https://en.cppreference.com/w/c/io/freopen",
},
],
[
"tmpfile",
{
header: "stdio.h",
nullMeaning: "Failed to create temp file",
docsUrl: "https://en.cppreference.com/w/c/io/tmpfile",
},
],
// String functions
[
"strstr",
{
header: "string.h",
nullMeaning: "Substring not found",
docsUrl: "https://en.cppreference.com/w/c/string/byte/strstr",
},
],
[
"strchr",
{
header: "string.h",
nullMeaning: "Character not found",
docsUrl: "https://en.cppreference.com/w/c/string/byte/strchr",
},
],
[
"strrchr",
{
header: "string.h",
nullMeaning: "Character not found",
docsUrl: "https://en.cppreference.com/w/c/string/byte/strrchr",
},
],
[
"memchr",
{
header: "string.h",
nullMeaning: "Byte not found",
docsUrl: "https://en.cppreference.com/w/c/string/byte/memchr",
},
],
// Environment
[
"getenv",
{
header: "stdlib.h",
nullMeaning: "Variable not found",
docsUrl: "https://en.cppreference.com/w/c/program/getenv",
},
],
]);
/**
* Functions that remain forbidden (dynamic allocation - ADR-003)
*/
const FORBIDDEN_FUNCTIONS: Set<string> = new Set([
"malloc",
"calloc",
"realloc",
"free",
]);
// ============================================================================
// Flow Analysis Data Structures (E0908)
// ============================================================================
/**
* State of a nullable variable with respect to NULL checking
*/
enum NullCheckState {
/** Variable has not been checked for NULL */
Unchecked = "unchecked",
/** Variable has been verified as not NULL */
CheckedNotNull = "checked_not_null",
}
/**
* Tracks the NULL check state of a single nullable variable
*/
interface INullableVariableState {
/** Variable name (with c_ prefix) */
name: string;
/** Line where the variable was declared */
declarationLine: number;
/** Type name (e.g., FILE, cstring) */
typeName: string;
/** Current NULL check state */
state: NullCheckState;
}
/**
* A scope for tracking nullable variable states.
* Scopes form a stack: function body -> if body -> nested if body, etc.
*/
interface INullCheckScope {
/** Map of variable name to state within this scope */
variables: Map<string, INullableVariableState>;
/** Parent scope (null for function-level scope) */
parent: INullCheckScope | null;
/** If this scope is from an if-statement, tracks if it's a guard clause */
isGuardClause: boolean;
/** Variable being checked in the if condition (for guard clause detection) */
guardVariable: string | null;
/** Whether the condition was == NULL (true) or != NULL (false) */
isNullEqualityCheck: boolean;
}
/**
* Listener that walks the parse tree and checks NULL usage
*/
class NullCheckListener extends CNextListener {
private readonly analyzer: NullCheckAnalyzer;
/** Whether we're currently inside an equality comparison (= or !=) */
private inEqualityComparison = false;
/** Track the function name in the current equality comparison (if any) */
private equalityComparisonFuncName: string | null = null;
/** Track if the current equality comparison contains NULL */
private equalityComparisonHasNull = false;
/** Track variable names in the current equality comparison */
private equalityComparisonVarNames: string[] = [];
/** Whether we're currently inside a variable declaration (with c_ prefix handling) */
private inVariableDeclarationWithNullable = false;
// ========================================================================
// Flow Analysis State (E0908)
// ========================================================================
/** Current scope for tracking nullable variable states */
private currentScope: INullCheckScope | null = null;
/** Stack of if-statement info for tracking nested conditions */
private readonly ifStack: Array<{
varName: string | null;
isNullCheck: boolean;
hasReturn: boolean;
}> = [];
/** Track if we're in the body of an if statement (first statement) */
private readonly inIfBody = false;
/** Track the current if-statement context for body detection */
private currentIfCtx: Parser.IfStatementContext | null = null;
/** Stack of while-statement info for tracking nested while conditions */
private readonly whileStack: Array<{
varName: string | null;
isNotNullCheck: boolean;
}> = [];
/** Track the current while-statement context for body detection */
private currentWhileCtx: Parser.WhileStatementContext | null = null;
constructor(analyzer: NullCheckAnalyzer) {
super();
this.analyzer = analyzer;
}
// ========================================================================
// Scope Management (E0908)
// ========================================================================
/**
* Create a new scope (e.g., entering a function or if-body)
*/
private pushScope(): void {
const newScope: INullCheckScope = {
variables: new Map(),
parent: this.currentScope,
isGuardClause: false,
guardVariable: null,
isNullEqualityCheck: false,
};
this.currentScope = newScope;
}
/**
* Exit the current scope and return to parent
*/
private popScope(): INullCheckScope | null {
const oldScope = this.currentScope;
Eif (this.currentScope) {
this.currentScope = this.currentScope.parent;
}
return oldScope;
}
/**
* Look up a variable's state in the current scope chain
*/
private lookupVariable(name: string): INullableVariableState | null {
let scope = this.currentScope;
while (scope) {
const state = scope.variables.get(name);
if (state) return state;
scope = scope.parent;
}
return null;
}
/**
* Update a variable's state in the scope where it's defined
*/
private updateVariableState(name: string, newState: NullCheckState): void {
let scope = this.currentScope;
while (scope) {
Eif (scope.variables.has(name)) {
const varState = scope.variables.get(name)!;
varState.state = newState;
return;
}
scope = scope.parent;
}
}
/**
* Register a c_ prefixed variable in the current scope
*/
private registerNullableVariable(
name: string,
typeName: string,
line: number,
): void {
if (!this.currentScope) return;
this.currentScope.variables.set(name, {
name,
declarationLine: line,
typeName,
state: NullCheckState.Unchecked,
});
}
// ========================================================================
// Function Scope Management (E0908)
// ========================================================================
override enterFunctionDeclaration = (
_ctx: Parser.FunctionDeclarationContext,
): void => {
// Create a new scope for the function body
this.pushScope();
};
override exitFunctionDeclaration = (
_ctx: Parser.FunctionDeclarationContext,
): void => {
// Exit the function scope
this.popScope();
};
// ========================================================================
// If-Statement Flow Analysis (E0908)
// ========================================================================
override enterIfStatement = (ctx: Parser.IfStatementContext): void => {
// Parse the condition to detect NULL checks
const condition = ctx.expression();
const conditionText = condition?.getText() ?? "";
// Check for patterns like "c_var != NULL" or "c_var = NULL"
const nullCheckMatch = /^(c_[a-zA-Z_]\w*)\s*(!?=)\s*NULL$/.exec(
conditionText,
);
if (nullCheckMatch) {
const varName = nullCheckMatch[1];
const operator = nullCheckMatch[2];
const isNotNullCheck = operator === "!=";
// Push info onto the if-stack for tracking
this.ifStack.push({
varName,
isNullCheck: !isNotNullCheck, // true if checking == NULL
hasReturn: false,
});
// For != NULL check, mark the variable as checked in the if-body
if (isNotNullCheck) {
// We'll set state to CheckedNotNull when entering the if-body
this.currentIfCtx = ctx;
}
} else {
// Not a null check, just track for nesting
this.ifStack.push({
varName: null,
isNullCheck: false,
hasReturn: false,
});
}
};
override exitIfStatement = (ctx: Parser.IfStatementContext): void => {
const ifInfo = this.ifStack.pop();
Iif (!ifInfo) return;
// Handle guard clause pattern: if (c_var == NULL) { return; }
// After such a guard, the variable is known to be not null
if (ifInfo.varName && ifInfo.isNullCheck && ifInfo.hasReturn) {
// This was a guard clause - the variable is checked after the if
const hasElse = ctx.ELSE() !== null;
if (!hasElse) {
this.updateVariableState(ifInfo.varName, NullCheckState.CheckedNotNull);
}
}
this.currentIfCtx = null;
};
/**
* Detect when we enter the body of an if or while statement
* For "if (c_var != NULL)" or "while (c_var != NULL)" the body has the variable checked
* SonarCloud S3776: Refactored to use helper methods.
*/
override enterStatement = (ctx: Parser.StatementContext): void => {
this.handleIfBranchNullCheck(ctx);
this.handleWhileBodyNullCheck(ctx);
};
/**
* Handle null-check for if statement "then" branch.
* SonarCloud S3776: Extracted from enterStatement().
*/
private handleIfBranchNullCheck(ctx: Parser.StatementContext): void {
if (!this.currentIfCtx || this.ifStack.length === 0) {
return;
}
const ifInfo = this.ifStack.at(-1)!;
if (ifInfo.isNullCheck || !ifInfo.varName) {
return;
}
const statements = this.currentIfCtx.statement();
if (statements.length > 0 && ctx === statements[0]) {
this.updateVariableState(ifInfo.varName, NullCheckState.CheckedNotNull);
}
}
/**
* Handle null-check for while statement body.
* SonarCloud S3776: Extracted from enterStatement().
*/
private handleWhileBodyNullCheck(ctx: Parser.StatementContext): void {
if (!this.currentWhileCtx || this.whileStack.length === 0) {
return;
}
const whileInfo = this.whileStack.at(-1)!;
if (!whileInfo.varName || !whileInfo.isNotNullCheck) {
return;
}
const whileBody = this.currentWhileCtx.statement();
if (whileBody === ctx) {
this.updateVariableState(
whileInfo.varName,
NullCheckState.CheckedNotNull,
);
}
}
override enterReturnStatement = (
_ctx: Parser.ReturnStatementContext,
): void => {
// Mark current if-statement (if any) as having a return
if (this.ifStack.length > 0) {
this.ifStack.at(-1)!.hasReturn = true;
}
};
// ========================================================================
// While-Statement Flow Analysis (E0908)
// ========================================================================
override enterWhileStatement = (ctx: Parser.WhileStatementContext): void => {
// Parse the condition to detect NULL checks
const condition = ctx.expression();
const conditionText = condition?.getText() ?? "";
// Check for patterns like "c_var != NULL"
const nullCheckMatch = /^(c_[a-zA-Z_]\w*)\s*!=\s*NULL$/.exec(conditionText);
if (nullCheckMatch) {
const varName = nullCheckMatch[1];
// Push info onto the while-stack for tracking
this.whileStack.push({
varName,
isNotNullCheck: true,
});
// For != NULL check, mark the variable as checked in the while-body
this.currentWhileCtx = ctx;
} else {
// Not a null check, just track for nesting
this.whileStack.push({
varName: null,
isNotNullCheck: false,
});
}
};
override exitWhileStatement = (_ctx: Parser.WhileStatementContext): void => {
this.whileStack.pop();
this.currentWhileCtx = null;
};
// ========================================================================
// Equality Comparison Context
// ========================================================================
override enterEqualityExpression = (
ctx: Parser.EqualityExpressionContext,
): void => {
// Check if this is actually a comparison (has = or !=)
// The grammar has equalityExpression : relationalExpression (('=' | '!=') relationalExpression)*
const children = ctx.children ?? [];
// Look for comparison operators
for (const child of children) {
const text = child.getText();
if (text === "=" || text === "!=") {
this.inEqualityComparison = true;
this.equalityComparisonFuncName = null;
this.equalityComparisonHasNull = false;
// Extract variable names from the comparison
this.equalityComparisonVarNames = this.extractVariableNames(ctx);
return;
}
}
};
/**
* Extract simple variable names from an equality expression
*/
private extractVariableNames(
ctx: Parser.EqualityExpressionContext,
): string[] {
const names: string[] = [];
// Get relational expressions (left and right sides of comparison)
const children = ctx.relationalExpression();
for (const child of children) {
const text = child.getText();
// Simple check: if it's a simple identifier and not NULL, add it
if (/^[a-zA-Z_]\w*$/.test(text) && text !== "NULL") {
names.push(text);
}
}
return names;
}
override exitEqualityExpression = (
ctx: Parser.EqualityExpressionContext,
): void => {
// Check if this was a comparison (has = or !=)
const children = ctx.children ?? [];
let isComparison = false;
for (const child of children) {
const text = child.getText();
if (text === "=" || text === "!=") {
isComparison = true;
break;
}
}
if (isComparison) {
// If we had a stream function in this comparison, it's OK
// (the function was used correctly in a NULL check)
this.inEqualityComparison = false;
this.equalityComparisonFuncName = null;
this.equalityComparisonHasNull = false;
this.equalityComparisonVarNames = [];
}
};
// ========================================================================
// Function Calls
// ========================================================================
override enterPostfixExpression = (
ctx: Parser.PostfixExpressionContext,
): void => {
const primary = ctx.primaryExpression();
if (!primary?.IDENTIFIER()) return;
const funcName = primary.IDENTIFIER()!.getText();
const ops = ctx.postfixOp();
// Check if it's a function call (has argument list or parens)
const isCall = ops.some((op) => {
const text = op.getText();
return text.startsWith("(");
});
if (!isCall) return;
const { line, column } = ParserUtils.getPosition(ctx);
// Check forbidden functions (always an error)
if (FORBIDDEN_FUNCTIONS.has(funcName)) {
this.analyzer.reportForbiddenFunction(funcName, line, column);
return;
}
// Check nullable C functions
if (NULLABLE_C_FUNCTIONS.has(funcName)) {
if (this.inEqualityComparison) {
// Track that we found a stream function in this comparison
this.equalityComparisonFuncName = funcName;
} else if (this.inVariableDeclarationWithNullable) {
// Inside a variable declaration - E0905 or valid c_ prefix already handled
// Don't also report E0901
} else {
// Stream function used outside of NULL comparison - error
this.analyzer.reportMissingNullCheck(funcName, line, column);
}
}
// E0908: Check for unchecked c_ variables passed as function arguments
this.checkFunctionArgumentsForUncheckedVariables(ctx, ops, line);
};
/**
* Check if any c_ prefixed variables in function arguments are unchecked (E0908)
*/
private checkFunctionArgumentsForUncheckedVariables(
ctx: Parser.PostfixExpressionContext,
ops: Parser.PostfixOpContext[],
line: number,
): void {
// Skip if we're in a NULL comparison context (the check itself)
if (this.inEqualityComparison) return;
for (const op of ops) {
const argList = op.argumentList();
if (!argList) continue;
// Get all expressions in the argument list
const args = argList.expression();
for (const arg of args) {
const argText = arg.getText();
// Check if argument is a simple c_ prefixed variable
if (/^c_[a-zA-Z_]\w*$/.test(argText)) {
const varState = this.lookupVariable(argText);
if (varState?.state === NullCheckState.Unchecked) {
const argLine = arg.start?.line ?? line;
const argColumn = arg.start?.column ?? 0;
this.analyzer.reportMissingNullCheckBeforeUse(
argText,
varState.typeName,
argLine,
argColumn,
);
}
}
}
}
}
// ========================================================================
// NULL Literal
// ========================================================================
override enterLiteral = (ctx: Parser.LiteralContext): void => {
const text = ctx.getText();
// Check for uppercase NULL (C library NULL)
if (text === "NULL") {
const { line, column } = ParserUtils.getPosition(ctx);
if (this.inEqualityComparison) {
// Check if any compared variable lacks c_ prefix and is not a nullable C function
for (const varName of this.equalityComparisonVarNames) {
if (
!NullCheckAnalyzer.hasNullablePrefix(varName) &&
!NULLABLE_C_FUNCTIONS.has(varName)
) {
this.analyzer.reportNullComparisonOnNonNullable(
varName,
line,
column,
);
}
}
// NULL in comparison context - OK (for c_ prefixed variables or functions)
this.equalityComparisonHasNull = true;
} else {
// NULL outside comparison - error
this.analyzer.reportInvalidNullUsage(line, column);
}
}
};
// ========================================================================
// Variable Assignment (check for storing stream function result)
// ========================================================================
override enterVariableDeclaration = (
ctx: Parser.VariableDeclarationContext,
): void => {
const expr = ctx.expression();
const varName = ctx.IDENTIFIER().getText();
const typeName = ctx.type()?.getText() ?? "unknown";
const identifierToken = ctx.IDENTIFIER().symbol;
const line = identifierToken.line;
const column = (identifierToken.column ?? 0) + 1; // 1-indexed column
// E0908: Register c_ prefixed variables for flow tracking
if (NullCheckAnalyzer.hasNullablePrefix(varName)) {
this.registerNullableVariable(varName, typeName, line);
}
if (!expr) return;
const funcName = this.extractFunctionCallName(expr);
// Check if assigning from a nullable C function
if (funcName && NULLABLE_C_FUNCTIONS.has(funcName)) {
// Set flag to suppress E0901 for the function call inside this declaration
this.inVariableDeclarationWithNullable = true;
// Must have c_ prefix
if (!NullCheckAnalyzer.hasNullablePrefix(varName)) {
this.analyzer.reportMissingCPrefix(
varName,
typeName,
funcName,
line,
column,
);
}
// If has c_ prefix, storage is allowed (don't report E0904 or E0901)
return;
}
// Check forbidden functions (malloc, etc.) - always error
if (funcName && FORBIDDEN_FUNCTIONS.has(funcName)) {
this.analyzer.reportForbiddenFunction(funcName, line, column);
return;
}
// Check for invalid c_ prefix on non-nullable types (E0906)
if (NullCheckAnalyzer.hasNullablePrefix(varName)) {
// If NOT assigning from nullable function AND type is NOT nullable, c_ prefix is invalid
Eif (!funcName || !NULLABLE_C_FUNCTIONS.has(funcName)) {
if (!NullCheckAnalyzer.isNullableCType(typeName)) {
this.analyzer.reportInvalidCPrefix(varName, typeName, line, column);
}
}
}
};
override exitVariableDeclaration = (): void => {
// Clear the flag when leaving variable declaration
this.inVariableDeclarationWithNullable = false;
};
override enterAssignmentStatement = (
ctx: Parser.AssignmentStatementContext,
): void => {
// Check if RHS contains a stream function call
const expr = ctx.expression();
const funcName = this.extractFunctionCallName(expr);
const target = ctx.assignmentTarget();
const varName = target.getText();
const { line, column } = ParserUtils.getPosition(ctx);
if (funcName && NULLABLE_C_FUNCTIONS.has(funcName)) {
// ADR-046: Allow reassignment to c_ prefixed variables (e.g., in while loops)
if (NullCheckAnalyzer.hasNullablePrefix(varName)) {
// Set flag to suppress E0901 for the function call inside this assignment
this.inVariableDeclarationWithNullable = true;
// E0908: Reset state to Unchecked on reassignment from nullable function
this.updateVariableState(varName, NullCheckState.Unchecked);
return;
}
this.analyzer.reportInvalidStorage(varName, funcName, line, column);
}
};
override exitAssignmentStatement = (): void => {
// Clear the flag when leaving assignment statement
this.inVariableDeclarationWithNullable = false;
};
/**
* Extract function call name from an expression (if it's a simple call)
*/
private extractFunctionCallName(
ctx: Parser.ExpressionContext,
): string | null {
// Simple heuristic: look for identifier followed by parens in text
// This could be improved with deeper AST analysis
const text = ctx.getText();
// Check nullable C functions
for (const funcName of NULLABLE_C_FUNCTIONS.keys()) {
if (text.includes(`${funcName}(`)) {
return funcName;
}
}
// Check forbidden functions
for (const funcName of FORBIDDEN_FUNCTIONS) {
if (text.includes(`${funcName}(`)) {
return funcName;
}
}
return null;
}
}
/**
* Analyzes C-Next AST for NULL safety violations
*/
class NullCheckAnalyzer {
private errors: INullCheckError[] = [];
/** Included headers (for context) */
private includedHeaders: Set<string> = new Set();
/**
* Analyze a parsed program for NULL safety errors
* @param tree The parsed program AST
* @returns Array of NULL check errors
*/
public analyze(tree: Parser.ProgramContext): INullCheckError[] {
this.errors = [];
this.includedHeaders = new Set();
// Collect included headers
this.collectIncludes(tree);
// Walk tree and check NULL usage
const listener = new NullCheckListener(this);
ParseTreeWalker.DEFAULT.walk(listener, tree);
return this.errors;
}
/**
* Collect included headers for context
*/
private collectIncludes(tree: Parser.ProgramContext): void {
for (const include of tree.includeDirective()) {
const text = include.getText();
const match = /#include\s*[<"]([^>"]+)[>"]/.exec(text);
Eif (match) {
this.includedHeaders.add(match[1]);
}
}
}
/**
* Check if stdio.h is included (required for stream functions)
*/
public hasStdioIncluded(): boolean {
return this.includedHeaders.has("stdio.h");
}
/**
* Report error: stream function used without NULL check
*/
public reportMissingNullCheck(
funcName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0901",
functionName: funcName,
line,
column,
message: `C library function '${funcName}' can return NULL - must check result`,
helpText: `Use: if (${funcName}(...) != NULL) { ... }`,
});
}
/**
* Report error: forbidden function (dynamic allocation - ADR-003)
*/
public reportForbiddenFunction(
funcName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0902",
functionName: funcName,
line,
column,
message: `Dynamic allocation function '${funcName}' is forbidden`,
helpText: "Dynamic allocation is forbidden by ADR-003",
});
}
/**
* Report error: NULL used outside comparison context
*/
public reportInvalidNullUsage(line: number, column: number): void {
this.errors.push({
code: "E0903",
functionName: "NULL",
line,
column,
message: "NULL can only be used in comparison context",
helpText: "Use: if (func(...) != NULL) or if (func(...) = NULL)",
});
}
/**
* Report error: trying to store stream function result in variable
*/
public reportInvalidStorage(
varName: string,
funcName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0904",
functionName: funcName,
line,
column,
message: `Cannot store '${funcName}' return value in variable '${varName}'`,
helpText: `C library pointer returns cannot be stored. Use direct comparison: if (${funcName}(...) != NULL)`,
});
}
/**
* Report error: missing c_ prefix for nullable C type (E0905)
*/
public reportMissingCPrefix(
varName: string,
typeName: string,
funcName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0905",
functionName: funcName,
line,
column,
message: `Missing 'c_' prefix for nullable C type '${typeName}'`,
helpText: `Variable '${varName}' stores nullable pointer from '${funcName}'. Use: ${typeName} c_${varName} <- ${funcName}(...)`,
});
}
/**
* Report error: c_ prefix on non-nullable type (E0906)
*/
public reportInvalidCPrefix(
varName: string,
typeName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0906",
functionName: varName,
line,
column,
message: `Invalid 'c_' prefix on non-nullable type '${typeName}'`,
helpText: `The 'c_' prefix is only for nullable C pointer types. Use: ${typeName} ${varName.substring(2)} <- ...`,
});
}
/**
* Report error: NULL comparison on non-nullable variable (E0907)
*/
public reportNullComparisonOnNonNullable(
varName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0907",
functionName: varName,
line,
column,
message: `NULL comparison on non-nullable variable '${varName}'`,
helpText: `Only variables with 'c_' prefix can be compared to NULL. C-Next variables are never null.`,
});
}
/**
* Report error: c_ variable used without prior NULL check (E0908)
*/
public reportMissingNullCheckBeforeUse(
varName: string,
typeName: string,
line: number,
column: number,
): void {
this.errors.push({
code: "E0908",
functionName: varName,
line,
column,
message: `Nullable variable '${varName}' used without NULL check`,
helpText: `Check for NULL before use: if (${varName} != NULL) { ... }`,
});
}
// ========================================================================
// c_ Prefix Validation Helpers (ADR-046)
// ========================================================================
/**
* Check if variable name has required c_ prefix for nullable C types
*/
public static hasNullablePrefix(varName: string): boolean {
return varName.startsWith("c_");
}
/**
* Check if a type is a nullable C pointer type
* Currently checks for FILE and pointer returns from NULLABLE_C_FUNCTIONS
*/
public static isNullableCType(typeName: string): boolean {
// FILE is always nullable
if (typeName === "FILE") return true;
// cstring (char*) from C functions is nullable
if (typeName === "cstring") return true;
// Pointer types from C headers
if (typeName.endsWith("*")) return true;
return false;
}
/**
* Get metadata for a nullable C function (for VS Code tooltips)
*/
public static getNullableFunctionInfo(
funcName: string,
): ICLibraryFunction | null {
return NULLABLE_C_FUNCTIONS.get(funcName) ?? null;
}
/**
* Check if a function is a nullable C function
*/
public static isNullableFunction(funcName: string): boolean {
return NULLABLE_C_FUNCTIONS.has(funcName);
}
/**
* Check if a function is forbidden (dynamic allocation - ADR-003)
*/
public static isForbiddenFunction(funcName: string): boolean {
return FORBIDDEN_FUNCTIONS.has(funcName);
}
/**
* Get nullable C functions that return struct pointers (FILE*, etc.)
* These need asterisk added to the type in code generation.
* Excludes char*-returning functions (fgets, strstr, etc.) which use cstring type.
*/
public static getStructPointerFunctions(): Set<string> {
return new Set(["fopen", "freopen", "tmpfile"]);
}
}
export default NullCheckAnalyzer;
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