Don't treat class-memaccess warning as error

Cache keys must be guaranteed to have no uninitialized bits so that they can be compared with memcmpy() and hash values can be computed from their raw memory representation. We do this by calling memset(this, ...) in the Memset<T> class used as the first base class. This is safe since no other constructor has run yet (similar to doing placement new in zeroed out memory). GCC 8.2's class-memset warning should thus not be treated as an error. Bug: b/135744933 Bug: b/134932616 Change-Id: I378b663281b1737359330c29c8c73934e7dd20f7 Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/33368Tested-by: Nicolas Capens <nicolascapens@google.com> Kokoro-Presubmit: kokoro <noreply+kokoro@google.com> Reviewed-by: Alexis Hétu <sugoi@google.com>

Don't treat class-memaccess warning as error
84b037e0 · Nicolas Capens · Nicolas Capens · 1f456938 · 84b037e0 · 84b037e0
Commit 84b037e0 authored Jun 25, 2019 by Nicolas Capens Committed by Nicolas Capens Jun 26, 2019
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CMakeLists.txt CMakeLists.txt +9 -0

LRUCache.hpp src/Device/LRUCache.hpp +1 -1

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--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -339,6 +339,15 @@ else()
        "-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"

--- a/src/Device/LRUCache.hpp
+++ b/src/Device/LRUCache.hpp
@@ -48,7 +48,7 @@ namespace sw
 	};

 	// Helper class for clearing the memory of objects at construction.
-	// Useful as the first base class or cache keys which may contain padding bytes or bits otherwise left uninitialized.
+	// Useful as the first base class of cache keys which may contain padding bytes or bits otherwise left uninitialized.
 	template<class T>
 	struct Memset
 	{