[GWP-ASan] Fixed issue with c++ standard library dependency.

[hctim]

Summary

Removed dependency on c++ standard library. Some supporting allocators (namely Scudo on Fuchsia, and shortly, scudo standalone) has a hard requirement of no c++stdlib.

This patch updates the build system so that we don't have any c++ stdlib dependencies. It also will conveniently fix a racy build-order bug discrepency between GWP-ASan and libc++.

[morehouse]

compiler-rt/lib/gwp_asan/CMakeLists.txt

13–16

"transient" - So Scudo's no-C++ library requirement will go away at some point?

[phosek]

LGTM, would it be possible to land this?

[hctim]

In D62048#1505972, @phosek wrote:

LGTM, would it be possible to land this?

Will do sometime in the next couple of hours when I can reach a laptop.

[hctim]

• /s/transient/delegated

compiler-rt/lib/gwp_asan/CMakeLists.txt

13–16

TIL I've been using this word wrong. /s/transient/delegated.

[hctim]

• Merge branch 'master' into gwp_asan/fix-c++stdlib

compiler-rt/lib/gwp_asan/CMakeLists.txt

 add_compiler_rt_component(gwp_asan)
 
 include_directories(..)
 
 set(GWP_ASAN_SOURCES
   random.cpp
 )
 
 set(GWP_ASAN_HEADERS
   random.h
 )
 
-# Disable RTTI and exception support, as we want these libraries to be
-# C-compatible. Regular C source files can be linked against the generated
-# GwpAsan libraries using the Clang C compiler.
-set(GWP_ASAN_CFLAGS -fno-rtti -fno-exceptions)
+# Ensure that GWP-ASan meets the delegated requirements of some supporting
+# allocators. Some supporting allocators (e.g. scudo standalone) cannot use any
+# parts of the C++ standard library.
+set(GWP_ASAN_CFLAGS -fno-rtti -fno-exceptions -nostdinc++)
 
 if (COMPILER_RT_HAS_GWP_ASAN)
   foreach(arch ${GWP_ASAN_SUPPORTED_ARCH})
     add_compiler_rt_runtime(
       clang_rt.gwp_asan
       STATIC
       ARCHS ${arch}
       SOURCES ${GWP_ASAN_SOURCES}

compiler-rt/lib/gwp_asan/random.h

 //===-- random.h ------------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef GWP_ASAN_RANDOM_H_
 #define GWP_ASAN_RANDOM_H_
 
-#include <cstdint>
+#include <stdint.h>
 
 namespace gwp_asan {
 // xorshift (32-bit output), extremely fast PRNG that uses arithmetic operations
 // only. Seeded using walltime.
 uint32_t getRandomUnsigned32();
 } // namespace gwp_asan
 
 #endif // GWP_ASAN_RANDOM_H_

compiler-rt/lib/gwp_asan/random.cpp

 //===-- random.cpp ----------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "gwp_asan/random.h"
 
-#include <ctime>
+#include <time.h>
 
 namespace gwp_asan {
 uint32_t getRandomUnsigned32() {
   thread_local uint32_t RandomState = static_cast<uint64_t>(time(nullptr));
   RandomState ^= RandomState << 13;
   RandomState ^= RandomState >> 17;
   RandomState ^= RandomState << 5;
   return RandomState;
 }
 } // namespace gwp_asan