issue-464: correctly handle realloc after memalign in debugalloc

debug memalign is creating special header block to allow us to find
real allocated block. And previous implementation of data copying
wasn't taking that into account and was copying that "alignment
header" into newly allocated block.

2 files changed, 31 insertions, 2 deletions

diff --git a/src/debugallocation.cc b/src/debugallocation.cc
index 180b709..454818d 100644
--- a/src/debugallocation.cc
+++ b/src/debugallocation.cc
@@ -1226,8 +1226,19 @@ extern "C" PERFTOOLS_DLL_DECL void* tc_realloc(void* ptr, size_t size) __THROW {
   // return null
   if (p == NULL)  return NULL;
 
-  memcpy(p->data_addr(), old->data_addr(),
-         (old->data_size() < size) ? old->data_size() : size);
+  // if ptr was allocated via memalign, then old->data_size() is not
+  // start of user data. So we must be careful to copy only user-data
+  char *old_begin = (char *)old->data_addr();
+  char *old_end = old_begin + old->data_size();
+
+  ssize_t old_ssize = old_end - (char *)ptr;
+  // TODO: make FromRawPointer check for out-of-bounds offset values
+  CHECK_CONDITION(old_ssize >= 0);
+
+  size_t old_size = (size_t)old_ssize;
+  CHECK_CONDITION(old_size <= old->data_size());
+
+  memcpy(p->data_addr(), ptr, (old_size < size) ? old_size : size);
   MallocHook::InvokeDeleteHook(ptr);
   MallocHook::InvokeNewHook(p->data_addr(), size);
   DebugDeallocate(ptr, MallocBlock::kMallocType);
diff --git a/src/tests/debugallocation_test.cc b/src/tests/debugallocation_test.cc
index f4a8567..beeb4cf 100644
--- a/src/tests/debugallocation_test.cc
+++ b/src/tests/debugallocation_test.cc
@@ -33,6 +33,8 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <malloc.h> // for memalign
+#include <string.h> // for memcmp
 #include <vector>
 #include "gperftools/malloc_extension.h"
 #include "base/logging.h"
@@ -296,6 +298,22 @@ TEST(DebugAllocationTest, HugeAlloc) {
 #endif
 }
 
+// based on test program contributed by mikesart@gmail.com aka
+// mikesart@valvesoftware.com. See issue-464.
+TEST(DebugAllocationTest, ReallocAfterMemalloc) {
+  char stuff[50];
+  memset(stuff, 0x11, sizeof(stuff));
+  void *p = memalign(16, sizeof(stuff));
+  EXPECT_NE(p, NULL);
+  memcpy(stuff, p, sizeof(stuff));
+
+  p = realloc(p, sizeof(stuff) + 10);
+  EXPECT_NE(p, NULL);
+
+  int rv = memcmp(stuff, p, sizeof(stuff));
+  EXPECT_EQ(rv, 0);
+}
+
 int main(int argc, char** argv) {
   // If you run without args, we run the non-death parts of the test.
   // Otherwise, argv[1] should be a number saying which death-test