[libcxxabi] Fix alignment of allocated exceptions in 32 bit builds
Summary:
In 32 bit builds on a 64 bit system `std::malloc` does not return correctly aligned memory. This leads to undefined behavior.
This patch switches to using `posix_memalign` to allocate correctly aligned memory instead.
Reviewers: mclow.lists, danalbert, jroelofs, compnerd
Reviewed By: compnerd
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D25417
git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@296952 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/cxa_exception.cpp b/src/cxa_exception.cpp
index 09e52ae..56d86cb 100644
--- a/src/cxa_exception.cpp
+++ b/src/cxa_exception.cpp
@@ -63,12 +63,16 @@
return cxa_exception_from_thrown_object(unwind_exception + 1 );
}
-static
-inline
-size_t
-cxa_exception_size_from_exception_thrown_size(size_t size)
-{
- return size + sizeof (__cxa_exception);
+// Round s up to next multiple of a.
+static inline
+size_t aligned_allocation_size(size_t s, size_t a) {
+ return (s + a - 1) & ~(a - 1);
+}
+
+static inline
+size_t cxa_exception_size_from_exception_thrown_size(size_t size) {
+ return aligned_allocation_size(size + sizeof (__cxa_exception),
+ alignof(__cxa_exception));
}
static void setExceptionClass(_Unwind_Exception* unwind_exception) {
@@ -140,7 +144,7 @@
void *__cxa_allocate_exception(size_t thrown_size) throw() {
size_t actual_size = cxa_exception_size_from_exception_thrown_size(thrown_size);
__cxa_exception *exception_header =
- static_cast<__cxa_exception *>(__malloc_with_fallback(actual_size));
+ static_cast<__cxa_exception *>(__aligned_malloc_with_fallback(actual_size));
if (NULL == exception_header)
std::terminate();
std::memset(exception_header, 0, actual_size);
@@ -150,7 +154,7 @@
// Free a __cxa_exception object allocated with __cxa_allocate_exception.
void __cxa_free_exception(void *thrown_object) throw() {
- __free_with_fallback(cxa_exception_from_thrown_object(thrown_object));
+ __aligned_free_with_fallback(cxa_exception_from_thrown_object(thrown_object));
}
@@ -159,7 +163,7 @@
// Otherwise, it will work like __cxa_allocate_exception.
void * __cxa_allocate_dependent_exception () {
size_t actual_size = sizeof(__cxa_dependent_exception);
- void *ptr = __malloc_with_fallback(actual_size);
+ void *ptr = __aligned_malloc_with_fallback(actual_size);
if (NULL == ptr)
std::terminate();
std::memset(ptr, 0, actual_size);
@@ -170,7 +174,7 @@
// This function shall free a dependent_exception.
// It does not affect the reference count of the primary exception.
void __cxa_free_dependent_exception (void * dependent_exception) {
- __free_with_fallback(dependent_exception);
+ __aligned_free_with_fallback(dependent_exception);
}