Move deprecated sancov functions to separate file.

[aarongreen]

Summary

The function moves the warnings about deprecated instrumentation from FuzzerTracePC.cpp to their own file, in order to facilitate their reuse in remote fuzzers.

This is change 12 of (at least) 20 for cross-process fuzzing support.

[aarongreen]

Multiprocess fuzzing will not be supported by the libFuzzer maintainers. Fuchsia has implemented a new approach with their Component Fuzzing Framework (RFC-117).

compiler-rt/lib/fuzzer/CMakeLists.txt

 set(LIBFUZZER_SOURCES
   FuzzerCrossOver.cpp
   FuzzerDataFlowTrace.cpp
+  FuzzerDeprecated.cpp
   FuzzerDriver.cpp
   FuzzerDSORelative.cpp
   FuzzerExtFunctionsDlsym.cpp
   FuzzerExtFunctionsWeak.cpp
   FuzzerExtFunctionsWindows.cpp
   FuzzerExtraCounters.cpp
   FuzzerFork.cpp
   FuzzerIO.cpp

compiler-rt/lib/fuzzer/FuzzerDeprecated.cpp

+//===- FuzzerDeprecated.cpp -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// Warns about deprecated instrumentation.
+//===----------------------------------------------------------------------===//
+
+#include "FuzzerUtil.h"
+
+namespace fuzzer {
+
+void WarnAboutDeprecatedInstrumentation(const char *flag) {
+  // Use RawPrint because Printf cannot be used on Windows before OutputFile is
+  // initialized.
+  RawPrint(flag);
+  RawPrint(
+      " is no longer supported by libFuzzer.\n"
+      "Please either migrate to a compiler that supports -fsanitize=fuzzer\n"
+      "or use an older version of libFuzzer\n");
+  exit(1);
+}
+
+} // namespace fuzzer
+
+extern "C" {
+ATTRIBUTE_INTERFACE
+ATTRIBUTE_NO_SANITIZE_ALL
+void __sanitizer_cov_trace_pc_guard(uint32_t *Guard) {
+  fuzzer::WarnAboutDeprecatedInstrumentation(
+      "-fsanitize-coverage=trace-pc-guard");
+}
+
+ATTRIBUTE_INTERFACE
+ATTRIBUTE_NO_SANITIZE_ALL
+void __sanitizer_cov_trace_pc() {
+  fuzzer::WarnAboutDeprecatedInstrumentation("-fsanitize-coverage=trace-pc");
+}
+
+ATTRIBUTE_INTERFACE
+void __sanitizer_cov_trace_pc_guard_init(uint32_t *Start, uint32_t *Stop) {
+  fuzzer::WarnAboutDeprecatedInstrumentation(
+      "-fsanitize-coverage=trace-pc-guard");
+}
+
+} // extern "C"

compiler-rt/lib/fuzzer/FuzzerTracePC.cpp

void TracePC::RecordInitialStack() {
   int stack;
   __sancov_lowest_stack = InitialStack = reinterpret_cast<uintptr_t>(&stack);
 }
 
 uintptr_t TracePC::GetMaxStackOffset() const {
   return InitialStack - __sancov_lowest_stack;  // Stack grows down
 }
 
-void WarnAboutDeprecatedInstrumentation(const char *flag) {
-  // Use RawPrint because Printf cannot be used on Windows before OutputFile is
-  // initialized.
-  RawPrint(flag);
-  RawPrint(
-      " is no longer supported by libFuzzer.\n"
-      "Please either migrate to a compiler that supports -fsanitize=fuzzer\n"
-      "or use an older version of libFuzzer\n");
-  exit(1);
-}
-
 } // namespace fuzzer
 
 extern "C" {
 ATTRIBUTE_INTERFACE
-ATTRIBUTE_NO_SANITIZE_ALL
-void __sanitizer_cov_trace_pc_guard(uint32_t *Guard) {
-  fuzzer::WarnAboutDeprecatedInstrumentation(
-      "-fsanitize-coverage=trace-pc-guard");
-}
-
-// Best-effort support for -fsanitize-coverage=trace-pc, which is available
-// in both Clang and GCC.
-ATTRIBUTE_INTERFACE
-ATTRIBUTE_NO_SANITIZE_ALL
-void __sanitizer_cov_trace_pc() {
-  fuzzer::WarnAboutDeprecatedInstrumentation("-fsanitize-coverage=trace-pc");
-}
-
-ATTRIBUTE_INTERFACE
-void __sanitizer_cov_trace_pc_guard_init(uint32_t *Start, uint32_t *Stop) {
-  fuzzer::WarnAboutDeprecatedInstrumentation(
-      "-fsanitize-coverage=trace-pc-guard");
-}
-
-ATTRIBUTE_INTERFACE
 void __sanitizer_cov_8bit_counters_init(uint8_t *Start, uint8_t *Stop) {
   fuzzer::TPC.HandleInline8bitCountersInit(Start, Stop);
 }
 
 ATTRIBUTE_INTERFACE
 void __sanitizer_cov_pcs_init(const uintptr_t *pcs_beg,
                               const uintptr_t *pcs_end) {
   fuzzer::TPC.HandlePCsInit(pcs_beg, pcs_end);