Barry Smith wrote:

Agreed this would be a good option to have. The question is how to do it without having a morass of nasty nested if-defs. Note that portably getting alignment out of malloc() alone is already ugly and not as simple a code as I would like.

To simplify things we could always require 16 byte alignment everywhere? But is that a desirable?

I doubt it's harmful, I don't think I understand where the nested ifdefs come in. The required alignment only needs to be stated in one place, I have something like the following in one of my projects. /* current */ #define PetscMalloc3(m1,t1,r1,m2,t2,r2,m3,t3,r3) \ (PetscMalloc((m1)*sizeof(t1)+(m2)*sizeof(t2)+(m3)*sizeof(t3),r1) \ || (*(r2) = (t2*)(*(r1)+m1), \ *(r3) = (t3*)(*(r2)+m2),0)) /* aligned */ #define PetscMalloc3(m1,t1,r1,m2,t2,r2,m3,t3,r3) \ (PetscMalloc((m1)*sizeof(t1)+(m2)*sizeof(t2)+(m3)*sizeof(t3)+2*(PETSC_MEMALIGN-1),r1) \ || (*(r2) = (t2*)PETSC_ALIGN(*(r1)+m1), \ *(r3) = (t3*)PETSC_ALIGN(*(r2)+m2),0)) #define PETSC_ALIGN(p) PetscNextAligned((uintptr_t)(p),PETSC_MEMALIGN-1) static inline void *PetscNextAligned(uintptr_t base,uintptr_t mask) {return (void*)((base + mask) & ~mask);} Note that this is a no-op if PETSC_MEMALIGN=1 and thus compiles to exactly what we have now. Jed