commit 6d874f057c1abb0af6f15bacada45e33beb9434a
author Nicolas Capens <capn@google.com> Wed Jun 26 10:31:47 2019 -0400
committer Nicolas Capens <nicolascapens@google.com> Thu Jun 27 14:16:29 2019 +0000
tree 84dc6c1df83edb0ff860048a319b29ac000a9cd3
parent 522d51219054a399e3533d760f8d6674ae71babc

Selectively suppress class-memaccess warning/error

To still produce the class-memaccess diagnostic on unintended cases,
suppress it only for our Memset<T> case and LLVM.

Bug: b/135744933
Change-Id: Id3b421a3b831600097d198ac793f582467d0a520
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/33429
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e67b96c..7cc7713 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -339,15 +339,6 @@
         "-Wmissing-braces"
     )
 
-    if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
-        if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 8)
-            list(APPEND SWIFTSHADER_COMPILE_OPTIONS
-                # Warnings that should not be treated as errors:
-                "-Wno-error=class-memaccess"  # TODO(b/134932616): Reliably initializing cache keys currently requires memset().
-            )
-        endif()
-    endif()
-
     if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         list(APPEND SWIFTSHADER_COMPILE_OPTIONS
             "-Wunused-lambda-capture"
@@ -1417,6 +1408,11 @@
         "-Wno-maybe-uninitialized"     # ‘X’ may be used uninitialized in this function
         "-Wno-unused-but-set-variable" # variable ‘X’ set but not used
     )
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 8)
+        list(APPEND LLVM_COMPILE_OPTIONS
+            "-Wno-class-memaccess"  # memset/memcmp used on non-trivial class object
+        )
+    endif()
 elseif(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
     list(APPEND LLVM_COMPILE_OPTIONS
         "/wd4141" # 'inline': used more than once

src/Device/LRUCache.hpp

diff --git a/src/Device/LRUCache.hpp b/src/Device/LRUCache.hpp
index 487d2a7..180b5b9 100644
--- a/src/Device/LRUCache.hpp
+++ b/src/Device/LRUCache.hpp
@@ -55,7 +55,21 @@
 		Memset(T *object, int val)
 		{
 			static_assert(std::is_base_of<Memset<T>, T>::value, "Memset<T> must only clear the memory of a type of which it is a base class");
+
+			// GCC 8+ warns that
+			// "‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘T’;
+			//  use assignment or value-initialization instead [-Werror=class-memaccess]"
+			// This is benign iff it happens before any of the base or member constructrs are called.
+			#if defined(__GNUC__) && (__GNUC__ >= 8)
+			#pragma GCC diagnostic push
+			#pragma GCC diagnostic ignored "-Wclass-memaccess"
+			#endif
+
 			memset(object, 0, sizeof(T));
+
+			#if defined(__GNUC__) && (__GNUC__ >= 8)
+			#pragma GCC diagnostic pop
+			#endif
 		}
 	};