Work around MemorySanitizer false-positive
The initialization of static thread-local data is not observed by
MemorySanitizer when inside a shared library, leading to false-positive
use-of-uninitialized-data errors:
https://github.com/google/sanitizers/issues/1409
We work around this by assigning an initial value to it ourselves on
first use. Note that since the flag to check whether this
initialization has already been done is itself a static thread-local,
we must suppress the MemorySanitizer check with a function attribute.
Bug: b/191050320
Change-Id: I356a89f90ff099e08a12f5562e0545ed14d93ee3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/55328
Tested-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@google.com>
diff --git a/src/Reactor/Pragma.cpp b/src/Reactor/Pragma.cpp
index 136be5e..0df95d7 100644
--- a/src/Reactor/Pragma.cpp
+++ b/src/Reactor/Pragma.cpp
@@ -17,16 +17,56 @@
#include "Debug.hpp"
-namespace rr {
+// The CLANG_NO_SANITIZE_MEMORY macro suppresses MemorySanitizer checks for
+// use-of-uninitialized-data. It is used to decorate functions with known
+// false positives.
+#ifdef __clang__
+# define CLANG_NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
+#else
+# define CLANG_NO_SANITIZE_MEMORY
+#endif
-static thread_local bool memorySanitizerInstrumentation = false;
+namespace {
+
+struct PragmaState
+{
+ bool memorySanitizerInstrumentation;
+};
+
+// The initialization of static thread-local data is not observed by MemorySanitizer
+// when inside a shared library, leading to false-positive use-of-uninitialized-data
+// errors: https://github.com/google/sanitizers/issues/1409
+// We work around this by assigning an initial value to it ourselves on first use.
+// Note that since the flag to check whether this initialization has already been
+// done is itself a static thread-local, we must suppress the MemorySanitizer check
+// with a function attribute.
+CLANG_NO_SANITIZE_MEMORY PragmaState &getPragmaState()
+{
+ static thread_local bool initialized = false;
+ static thread_local PragmaState state;
+
+ if(!initialized)
+ {
+ state = {};
+
+ initialized = true;
+ }
+
+ return state;
+}
+
+} // namespace
+
+namespace rr {
void Pragma(PragmaBooleanOption option, bool enable)
{
+ PragmaState &state = ::getPragmaState();
+
switch(option)
{
case MemorySanitizerInstrumentation:
- memorySanitizerInstrumentation = enable;
+ state.memorySanitizerInstrumentation = enable;
break;
default:
UNSUPPORTED("Unknown pragma %d", int(option));
@@ -35,10 +75,12 @@
bool getPragmaState(PragmaBooleanOption option)
{
+ PragmaState &state = ::getPragmaState();
+
switch(option)
{
case MemorySanitizerInstrumentation:
- return memorySanitizerInstrumentation;
+ return state.memorySanitizerInstrumentation;
default:
UNSUPPORTED("Unknown pragma %d", int(option));
return false;
