Improve alignment handling for the alignment allocator

Alc/hrtf.cpp

@@ -66,7 +66,7 @@ struct HrtfHandle {
 
 std::unique_ptr<HrtfHandle> HrtfHandle::Create(size_t fname_len)
 {
-    void *ptr{al_calloc(DEF_ALIGN, HrtfHandle::Sizeof(fname_len))};
+    void *ptr{al_calloc(alignof(HrtfHandle), HrtfHandle::Sizeof(fname_len))};
     return std::unique_ptr<HrtfHandle>{new (ptr) HrtfHandle{fname_len}};
 }
 

OpenAL32/alAuxEffectSlot.cpp

@@ -246,7 +246,7 @@ ALeffectslotArray *ALeffectslot::CreatePtrArray(size_t count) noexcept
     /* Allocate space for twice as many pointers, so the mixer has scratch
      * space to store a sorted list during mixing.
      */
-    void *ptr{al_calloc(DEF_ALIGN, ALeffectslotArray::Sizeof(count*2))};
+    void *ptr{al_calloc(alignof(ALeffectslotArray), ALeffectslotArray::Sizeof(count*2))};
     return new (ptr) ALeffectslotArray{count};
 }
 

common/almalloc.cpp

@@ -3,6 +3,7 @@
 
 #include "almalloc.h"
 
+#include <cassert>
 #include <cstdlib>
 #include <cstring>
 #ifdef HAVE_MALLOC_H
@@ -26,6 +27,9 @@
 
 void *al_malloc(size_t alignment, size_t size)
 {
+    assert((alignment & (alignment-1)) == 0);
+    alignment = std::max(alignment, sizeof(void*));
+
 #if defined(HAVE_ALIGNED_ALLOC)
     size = (size+(alignment-1))&~(alignment-1);
     return aligned_alloc(alignment, size);

common/almalloc.h

@@ -39,7 +39,7 @@ int al_is_sane_alignment_allocator(void) noexcept;
 
 namespace al {
 
-template<typename T, size_t alignment=DEF_ALIGN>
+template<typename T, size_t alignment=alignof(T)>
 struct allocator : public std::allocator<T> {
     using size_type = size_t;
     using pointer = T*;
@@ -97,7 +97,7 @@ std::unique_ptr<T> make_unique(ArgsT&&...args)
  * struct, with placement new, to have a run-time-sized array that's embedded
  * with its size.
  */
-template<typename T,size_t alignment=DEF_ALIGN>
+template<typename T, size_t alignment=alignof(T)>
 struct FlexArray {
     const size_t mSize;
     alignas(alignment) T mArray[];