Add valgrind support to our garbage collector

Tell valgrind about the memory we allocate and free in the
garbage collector. Also mark stack variables as initialized
before walking the stack.

This avoids all valgrind warnings related to GC and gives
proper warnings if we should attempt to access garbage collected
memory.

Change-Id: I7e923a163c25e7a5b4409b1b9c2191f314675f2d
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

3 files changed, 40 insertions, 2 deletions

diff --git a/src/v4/qv4managed.cpp b/src/v4/qv4managed.cpp
index 30219b9afe..ab87b9dd9f 100644
--- a/src/v4/qv4managed.cpp
+++ b/src/v4/qv4managed.cpp
@@ -77,6 +77,8 @@ void Managed::operator delete(void *ptr)
         return;
 
     Managed *m = static_cast<Managed *>(ptr);
+    m->vtbl = 0;
+    m->_data = 0;
     m->~Managed();
 }
 
diff --git a/src/v4/qv4mm.cpp b/src/v4/qv4mm.cpp
index 8c62d64a74..c43bb3e369 100644
--- a/src/v4/qv4mm.cpp
+++ b/src/v4/qv4mm.cpp
@@ -43,6 +43,11 @@
 #include <cstdlib>
 #include "qv4alloca_p.h"
 
+#ifdef V4_USE_VALGRIND
+#include <valgrind/valgrind.h>
+#include <valgrind/memcheck.h>
+#endif
+
 using namespace QQmlJS::VM;
 using namespace WTF;
 
@@ -112,6 +117,9 @@ MemoryManager::MemoryManager()
     : m_d(new Data(true))
 {
     setEnableGC(true);
+#ifdef V4_USE_VALGRIND
+    VALGRIND_CREATE_MEMPOOL(this, 0, true);
+#endif
 }
 
 Managed *MemoryManager::alloc(std::size_t size)
@@ -170,9 +178,16 @@ Managed *MemoryManager::alloc(std::size_t size)
         *last = 0;
         m = m_d->smallItems[pos];
         m_d->availableItems[pos] += allocation.memory.size()/size - 1;
+#ifdef V4_USE_VALGRIND
+        VALGRIND_MAKE_MEM_NOACCESS(allocation.memory, allocation.chunkSize);
+#endif
     }
 
   found:
+#ifdef V4_USE_VALGRIND
+    VALGRIND_MEMPOOL_ALLOC(this, m, size);
+#endif
+
     m_d->smallItems[pos] = m->nextFree();
     return m;
 }
@@ -234,6 +249,9 @@ std::size_t MemoryManager::sweep(char *chunkStart, std::size_t chunkSize, size_t
 
     Managed **f = &m_d->smallItems[size >> 4];
 
+#ifdef V4_USE_VALGRIND
+    VALGRIND_DISABLE_ERROR_REPORTING;
+#endif
     for (char *chunk = chunkStart, *chunkEnd = chunk + chunkSize - size; chunk <= chunkEnd; chunk += size) {
         Managed *m = reinterpret_cast<Managed *>(chunk);
 //        qDebug("chunk @ %p, size = %lu, in use: %s, mark bit: %s",
@@ -246,15 +264,25 @@ std::size_t MemoryManager::sweep(char *chunkStart, std::size_t chunkSize, size_t
                 m->markBit = 0;
             } else {
 //                qDebug() << "-- collecting it." << m << *f << m->nextFree();
+#ifdef V4_USE_VALGRIND
+                VALGRIND_ENABLE_ERROR_REPORTING;
+#endif
                 m->vtbl->destroy(m);
 
                 m->setNextFree(*f);
+#ifdef V4_USE_VALGRIND
+                VALGRIND_DISABLE_ERROR_REPORTING;
+                VALGRIND_MEMPOOL_FREE(this, m);
+#endif
                 *f = m;
                 SCRIBBLE(m, 0x99, size);
                 ++freedCount;
             }
         }
     }
+#ifdef V4_USE_VALGRIND
+    VALGRIND_ENABLE_ERROR_REPORTING;
+#endif
 
     return freedCount;
 }
@@ -358,11 +386,11 @@ void MemoryManager::willAllocate(std::size_t size)
 
 void MemoryManager::collectFromStack() const
 {
+    quintptr valueOnStack = 0;
+
     if (!m_d->heapChunks.count())
         return;
 
-    quintptr valueOnStack = 0;
-
 #if USE(PTHREADS)
 #  if OS(DARWIN)
     void* stackTop = 0;
@@ -392,6 +420,10 @@ void MemoryManager::collectFromStack() const
     quintptr *current = (&valueOnStack) + 1;
 //    qDebug() << "collectFromStack";// << top << current << &valueOnStack;
 
+#if V4_USE_VALGRIND
+    VALGRIND_MAKE_MEM_DEFINED(current, (top - current)*sizeof(quintptr));
+#endif
+
     char** heapChunkBoundaries = (char**)alloca(m_d->heapChunks.count() * 2 * sizeof(char*));
     char** heapChunkBoundariesEnd = heapChunkBoundaries + 2 * m_d->heapChunks.count();
     int i = 0;
diff --git a/src/v4/v4.pro b/src/v4/v4.pro
index 447df2fc7c..80444b89fa 100644
--- a/src/v4/v4.pro
+++ b/src/v4/v4.pro
@@ -163,6 +163,10 @@ debug-with-libunwind {
     DEFINES += WTF_USE_LIBUNWIND_DEBUG=1
 }
 
+valgrind {
+    DEFINES += V4_USE_VALGRIND
+}
+
 include(moth/moth.pri)
 include(../3rdparty/masm/masm.pri)
 include(../3rdparty/double-conversion/double-conversion.pri)