Fix SIGBUS due to unaligned access
Update RAPIDJSON_ALIGN() to always align on an 8-byte boundary
unless otherwise overridden.
On some platforms (such as ARM), 64-bit items (such as doubles and
64-bit integers) must be aligned to an 8 byte address, even though the
architecture is only 32-bits. On these platforms, MemoryPoolAllocator
must match the malloc() behavior and return a 8 byte aligned allocation.
This eliminates any alignment issues that may occur at the expense of
additional memory overhead.
Failure to do so caused a SIGBUS signal when calling
GenericValue::SetNull(). The size of the data_ member of the
GenericValue class is 16 bytes in 32-bit mode and its constructor
requires an 8-byte aligned access.
While parsing a JSON formatted string using Document::ParseStream(), a
stack object containing GenericValue items was constructed. Since the
stack was 8-byte aligned, the constructor calls would succeed. When the
lifetime of the object ends, SetObjectRaw() is invoked. This triggered
an allocation with 4-byte alignment to which the previously 8-byte
aligned GenericValue array was copied. After this, any call to a
GenericValue API that triggered the constructor and thus the placement
new operation on the Data type member would trigger a SIGBUS.
Signed-off-by: Veselin Georgiev <veselin.georgiev@garmin.com>
Signed-off-by: Joshua Watt <Joshua.Watt@garmin.com>
diff --git a/include/rapidjson/rapidjson.h b/include/rapidjson/rapidjson.h
index a256c86..8cff38c 100644
--- a/include/rapidjson/rapidjson.h
+++ b/include/rapidjson/rapidjson.h
@@ -269,16 +269,11 @@
/*! \ingroup RAPIDJSON_CONFIG
\param x pointer to align
- Some machines require strict data alignment. Currently the default uses 4 bytes
- alignment on 32-bit platforms and 8 bytes alignment for 64-bit platforms.
+ Some machines require strict data alignment. The default is 8 bytes.
User can customize by defining the RAPIDJSON_ALIGN function macro.
*/
#ifndef RAPIDJSON_ALIGN
-#if RAPIDJSON_64BIT == 1
-#define RAPIDJSON_ALIGN(x) (((x) + static_cast<uint64_t>(7u)) & ~static_cast<uint64_t>(7u))
-#else
-#define RAPIDJSON_ALIGN(x) (((x) + 3u) & ~3u)
-#endif
+#define RAPIDJSON_ALIGN(x) (((x) + static_cast<size_t>(7u)) & ~static_cast<size_t>(7u))
#endif
///////////////////////////////////////////////////////////////////////////////
diff --git a/test/unittest/allocatorstest.cpp b/test/unittest/allocatorstest.cpp
index a5958de..2202c11 100644
--- a/test/unittest/allocatorstest.cpp
+++ b/test/unittest/allocatorstest.cpp
@@ -63,23 +63,21 @@
}
TEST(Allocator, Alignment) {
-#if RAPIDJSON_64BIT == 1
- EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000000), RAPIDJSON_ALIGN(0));
- for (uint64_t i = 1; i < 8; i++) {
- EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008), RAPIDJSON_ALIGN(i));
- EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000010), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008) + i));
- EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000001, 0x00000000), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0xFFFFFFF8) + i));
- EXPECT_EQ(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF8), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF0) + i));
+ if (sizeof(size_t) >= 8) {
+ EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000000), RAPIDJSON_ALIGN(0));
+ for (uint64_t i = 1; i < 8; i++) {
+ EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008), RAPIDJSON_ALIGN(i));
+ EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000010), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008) + i));
+ EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000001, 0x00000000), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0xFFFFFFF8) + i));
+ EXPECT_EQ(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF8), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF0) + i));
+ }
}
-#else
+
EXPECT_EQ(0u, RAPIDJSON_ALIGN(0u));
- for (uint32_t i = 1; i < 4; i++) {
- EXPECT_EQ(4u, RAPIDJSON_ALIGN(i));
- EXPECT_EQ(8u, RAPIDJSON_ALIGN(4u + i));
- EXPECT_EQ(0xFFFFFFF8u, RAPIDJSON_ALIGN(0xFFFFFFF4u + i));
- EXPECT_EQ(0xFFFFFFFCu, RAPIDJSON_ALIGN(0xFFFFFFF8u + i));
+ for (uint32_t i = 1; i < 8; i++) {
+ EXPECT_EQ(8u, RAPIDJSON_ALIGN(i));
+ EXPECT_EQ(0xFFFFFFF8u, RAPIDJSON_ALIGN(0xFFFFFFF0u + i));
}
-#endif
}
TEST(Allocator, Issue399) {
