Fix centipede:coverage_test under ubsan.

This is done by disabling coverage instrumentation for input printing in test_fuzz_target, which introduces coverage noise under ubsan.

PiperOrigin-RevId: 986183783

centipede/control_flow_test.cc

diff --git a/centipede/control_flow_test.cc b/centipede/control_flow_test.cc
index 3fe2282..0c687c7 100644
--- a/centipede/control_flow_test.cc
+++ b/centipede/control_flow_test.cc
@@ -313,7 +313,7 @@
       has_llvm_fuzzer_test_one_input = true;
       EXPECT_THAT(
           symbols.location(i),
-          testing::HasSubstr("centipede/testing/test_fuzz_target.cc:73"));
+          testing::HasSubstr("centipede/testing/test_fuzz_target.cc:84"));
     }
   }
   EXPECT_TRUE(has_llvm_fuzzer_test_one_input);

centipede/testing/centipede_main_test.sh

diff --git a/centipede/testing/centipede_main_test.sh b/centipede/testing/centipede_main_test.sh
index a74e8ad..53e5919 100755
--- a/centipede/testing/centipede_main_test.sh
+++ b/centipede/testing/centipede_main_test.sh
@@ -74,7 +74,7 @@
     --symbolizer_path="${LLVM_SYMBOLIZER}" | tee "${LOG}"
   fuzztest::internal::assert_regex_in_file 'Custom mutator detected; will use it' "${LOG}"
   # Note: the test assumes LLVMFuzzerTestOneInput is defined on a specific line.
-  fuzztest::internal::assert_regex_in_file "FUNC: LLVMFuzzerTestOneInput .*testing/test_fuzz_target.cc:73" "${LOG}"
+  fuzztest::internal::assert_regex_in_file "FUNC: LLVMFuzzerTestOneInput .*testing/test_fuzz_target.cc:84" "${LOG}"
   fuzztest::internal::assert_regex_in_file "EDGE: LLVMFuzzerTestOneInput .*testing/test_fuzz_target.cc" "${LOG}"
 
   echo "============ ${FUNC}: add func1/func2-A inputs to the corpus."

centipede/testing/test_fuzz_target.cc

diff --git a/centipede/testing/test_fuzz_target.cc b/centipede/testing/test_fuzz_target.cc
index 37ad23d..99217b7 100644
--- a/centipede/testing/test_fuzz_target.cc
+++ b/centipede/testing/test_fuzz_target.cc
@@ -62,6 +62,17 @@
 static int non_cost_global[10];
 static const int const_global[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
 
+__attribute__((noinline, no_sanitize("coverage"))) void PrintInput(
+    const uint8_t* data, size_t size) {
+  printf("{");
+  for (size_t i = 0; i < size; i++) {
+    // This loop generates different coverage counters
+    // depending on the number of iterations.
+    printf("%02x%s", (int)data[i], i + 1 == size ? "" : ", ");
+  }
+  printf("}\n");
+}
+
 // See https://llvm.org/docs/LibFuzzer.html#fuzz-target.
 // control_flow_test.cc and centipede_main_test.sh verify the exact line where
 // LLVMFuzzerTestOneInput is declared.
@@ -72,13 +83,7 @@
 static volatile void *ptr_sink = nullptr;
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   // Print the input. It will be tested in runner_test.
-  printf("{");
-  for (size_t i = 0; i < size; i++) {
-    // This loop generates different coverage counters
-    // depending on the number of iterations.
-    printf("%02x%s", (int)data[i], i + 1 == size ? "" : ", ");
-  }
-  printf("}\n");
+  PrintInput(data, size);
 
   // If the input is 'cntX', run X iterations of a do-while loop.
   // Runs one iteration if X is 0. Used to test --use_counter_features.