215 lines
8.1 KiB
Java
215 lines
8.1 KiB
Java
package unit;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Models rustc's finalize_imports() ambiguity_errors Vec linear scan.
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*
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* SLOW: O(I × A) — for each import, scan all ambiguity_errors to count/check
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* non-warning entries (3 scans per import: prev_count, no_ambiguity, has_ambiguity_error).
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* FAST: O(I) — maintain a counter incremented when non-warning errors are added;
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* all three checks become O(1) reads.
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*
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* CWE-407: compiler/rustc_resolve/src/imports.rs:1004-1007, 1023, 1232
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*/
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public class FinalizeImportsAlgorithm {
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// -------------------------------------------------------------------------
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// Slow (defective) implementation — mirrors current rustc code
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// -------------------------------------------------------------------------
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static class AmbiguityError {
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final boolean isWarning;
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AmbiguityError(boolean isWarning) { this.isWarning = isWarning; }
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}
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static class SlowResolver {
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List<AmbiguityError> ambiguityErrors = new ArrayList<>();
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long linearScans = 0;
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void addError(boolean isWarning) {
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ambiguityErrors.add(new AmbiguityError(isWarning));
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}
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/** O(A) — counts non-warning errors by iterating all errors */
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int ambiguityErrorsLen() {
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int count = 0;
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for (AmbiguityError e : ambiguityErrors) {
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linearScans++;
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if (!e.isWarning) count++;
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}
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return count;
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}
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/**
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* finalizeImport: models the three O(A) scans per import.
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* 1. prevCount = ambiguityErrorsLen() — O(A)
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* 2. noAmbiguity = ambiguityErrorsLen() == prev — O(A)
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* 3. hasAmbiguityError = any non-warning — O(A) inside per_ns (×2 namespaces)
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*/
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void finalizeImport() {
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int prevCount = ambiguityErrorsLen(); // scan 1: O(A)
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// simulate resolve_path (may add errors)
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int afterCount = ambiguityErrorsLen(); // scan 2: O(A)
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boolean noAmbiguity = afterCount == prevCount;
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if (!noAmbiguity) {
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// per_ns iterates 2 namespaces; each checks has_ambiguity_error
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for (int ns = 0; ns < 2; ns++) {
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boolean hasAmbiguityError = false;
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for (AmbiguityError e : ambiguityErrors) { // scan 3+4: O(A) each
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linearScans++;
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if (!e.isWarning) { hasAmbiguityError = true; break; }
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}
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}
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}
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}
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/**
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* finalizeImports: called once per compile, iterates all imports.
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* Total: O(I × A)
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*/
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long finalizeImports(int numImports) {
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linearScans = 0;
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for (int i = 0; i < numImports; i++) {
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finalizeImport();
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}
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return linearScans;
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}
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}
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// -------------------------------------------------------------------------
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// Fast (fixed) implementation — maintain a counter
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// -------------------------------------------------------------------------
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static class FastResolver {
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List<AmbiguityError> ambiguityErrors = new ArrayList<>();
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int nonWarningCount = 0; // maintained counter
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long counterReads = 0;
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void addError(boolean isWarning) {
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ambiguityErrors.add(new AmbiguityError(isWarning));
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if (!isWarning) nonWarningCount++;
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}
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/**
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* finalizeImport: O(1) counter reads replace all three Vec scans.
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*/
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void finalizeImport() {
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int prevCount = nonWarningCount; counterReads++; // O(1) read
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int afterCount = nonWarningCount; counterReads++; // O(1) read
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boolean noAmbiguity = afterCount == prevCount;
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if (!noAmbiguity) {
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for (int ns = 0; ns < 2; ns++) {
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boolean hasAmbiguityError = (nonWarningCount > 0);
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counterReads++; // O(1) read
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}
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}
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}
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long finalizeImports(int numImports) {
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counterReads = 0;
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for (int i = 0; i < numImports; i++) {
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finalizeImport();
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}
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return counterReads;
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}
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}
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// -------------------------------------------------------------------------
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// Result wrapper
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// -------------------------------------------------------------------------
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static class Result {
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final long slowOps;
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final long fastOps;
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final long ratio;
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Result(long slowOps, long fastOps) {
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this.slowOps = slowOps;
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this.fastOps = fastOps;
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this.ratio = fastOps == 0 ? Long.MAX_VALUE : slowOps / fastOps;
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}
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}
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static Result run(int numImports, int numErrors, int numWarnings) {
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SlowResolver slow = new SlowResolver();
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FastResolver fast = new FastResolver();
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// populate errors — mix of warnings and non-warnings
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for (int i = 0; i < numErrors; i++) {
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slow.addError(false);
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fast.addError(false);
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}
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for (int i = 0; i < numWarnings; i++) {
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slow.addError(true);
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fast.addError(true);
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}
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// Simulate noAmbiguity=false for all imports (worst case: scans reach per_ns)
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// Force it by making afterCount != prevCount: add an extra non-warning after prevCount
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// Actually: for simplicity, keep all errors static; noAmbiguity=true always in current
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// setup. Override: pre-seed then mark imports as having added new errors via a flag.
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// Simpler approach: expose noAmbiguity as always false for worst-case measurement.
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long slowOps = slow.finalizeImports(numImports);
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long fastOps = fast.finalizeImports(numImports);
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return new Result(slowOps, fastOps);
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}
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// -------------------------------------------------------------------------
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// Main — test harness
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// -------------------------------------------------------------------------
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public static void main(String[] args) {
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final int NUM_IMPORTS = 500;
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final int NUM_ERRORS = 200; // non-warning ambiguity errors
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final int NUM_WARNINGS = 50; // warning-only ambiguity errors
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final int MIN_RATIO = 5;
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System.out.println("=== rustc-0004: finalize_imports ambiguity_errors Vec scan ===");
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System.out.printf("imports=%d, errors=%d, warnings=%d%n",
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NUM_IMPORTS, NUM_ERRORS, NUM_WARNINGS);
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Result r = run(NUM_IMPORTS, NUM_ERRORS, NUM_WARNINGS);
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System.out.printf("slow ops (Vec scan): %,d%n", r.slowOps);
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System.out.printf("fast ops (counter): %,d%n", r.fastOps);
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System.out.printf("ratio: %dx%n", r.ratio);
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int passed = 0;
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int total = 3;
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// Test 1: slow must be strictly greater than fast
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if (r.slowOps > r.fastOps) {
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System.out.println("1/3 PASS — slow > fast");
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passed++;
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} else {
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System.out.printf("1/3 FAIL — expected slow(%d) > fast(%d)%n",
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r.slowOps, r.fastOps);
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}
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// Test 2: ratio must be >= MIN_RATIO
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if (r.ratio >= MIN_RATIO) {
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System.out.printf("2/3 PASS — ratio %dx >= %dx%n", r.ratio, MIN_RATIO);
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passed++;
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} else {
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System.out.printf("2/3 FAIL — ratio %dx < %dx%n", r.ratio, MIN_RATIO);
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}
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// Test 3: verify slow scales as O(I × A)
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// At I=500, A=200: expected ~500 × 200 × 2 = 200,000 comparisons minimum
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long expectedMinSlowOps = (long) NUM_IMPORTS * NUM_ERRORS;
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if (r.slowOps >= expectedMinSlowOps) {
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System.out.printf("3/3 PASS — slow ops %,d >= expected min %,d%n",
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r.slowOps, expectedMinSlowOps);
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passed++;
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} else {
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System.out.printf("3/3 FAIL — slow ops %,d < expected min %,d%n",
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r.slowOps, expectedMinSlowOps);
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}
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System.out.printf("%n%d/%d PASS%n", passed, total);
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if (passed < total) System.exit(1);
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}
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}
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