Patch: update instrumentation order to fix coverage (#711)

Co-authored-by: Kostiantyn Melnik <[email protected]> Co-authored-by: Fabian Meumertzheim <[email protected]>
CodeIntelligenceTesting · Apr 26, 2023 · c2e8901 · c2e8901
1 parent d68158d
commit c2e8901
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Showing 2 changed files with 8 additions and 7 deletions.
diff --git a/src/main/java/com/code_intelligence/jazzer/agent/RuntimeInstrumentor.kt b/src/main/java/com/code_intelligence/jazzer/agent/RuntimeInstrumentor.kt
@@ -214,12 +214,9 @@ class RuntimeInstrumentor(
         }
         return ClassInstrumentor(internalClassName, bytecode).run {
             if (fullInstrumentation) {
-                // Hook instrumentation must be performed after data flow tracing as the injected
-                // bytecode would trigger the GEP callbacks for byte[]. Coverage instrumentation
-                // must be performed after hook instrumentation as the injected bytecode would
-                // trigger the GEP callbacks for ByteBuffer.
-                traceDataFlow(instrumentationTypes)
-                hooks(includedHooks + customHooks, classWithHooksEnabledField)
+                // Coverage instrumentation must be performed before any other code updates
+                // or there will be additional coverage points injected if any calls are inserted
+                // and JaCoCo will produce a broken coverage report.
                 coverageIdSynchronizer.withIdForClass(internalClassName) { firstId ->
                     coverage(firstId).also { actualNumEdgeIds ->
                         CoverageRecorder.recordInstrumentedClass(
@@ -230,6 +227,10 @@ class RuntimeInstrumentor(
                         )
                     }
                 }
+                // Hook instrumentation must be performed after data flow tracing as the injected
+                // bytecode would trigger the GEP callbacks for byte[].
+                traceDataFlow(instrumentationTypes)
+                hooks(includedHooks + customHooks, classWithHooksEnabledField)
             } else {
                 hooks(customHooks, classWithHooksEnabledField)
             }

diff --git a/tests/src/test/java/com/example/CoverageFuzzer.java b/tests/src/test/java/com/example/CoverageFuzzer.java
@@ -171,7 +171,7 @@ private static void assertCoverageDump() throws IOException {
     assertEquals(7, countHits(coverageFuzzerCoverage.getProbes()));
 
     assertEquals("com/example/CoverageFuzzer$ClassToCover", classToCoverCoverage.getName());
-    assertEquals(11, countHits(classToCoverCoverage.getProbes()));
+    assertEquals(10, countHits(classToCoverCoverage.getProbes()));
   }
 
   private static int countHits(boolean[] probes) {