Make use of GCC alloc_align attribute

This lets the compiler know about the alignment of pointers returned
by aligned_alloc(3), posix_memalign(3). and contigmalloc(9)

Currently this is only supported in recent gcc but we are ready to
use it if clang implements it.

Relnotes:	yes

2 files changed, 4 insertions, 3 deletions

diff --git a/include/stdlib.h b/include/stdlib.h
index a5ef0e7..d5506ff 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -156,7 +156,8 @@ _Noreturn void	 _Exit(int);
  * If we're in a mode greater than C99, expose C11 functions.
  */
 #if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
-void *	aligned_alloc(size_t, size_t) __malloc_like __alloc_size(2);
+void *	aligned_alloc(size_t, size_t) __malloc_like __alloc_align(1)
+	    __alloc_size(2);
 int	at_quick_exit(void (*)(void));
 _Noreturn void
 	quick_exit(int);
@@ -171,7 +172,7 @@ char	*realpath(const char * __restrict, char * __restrict);
 int	 rand_r(unsigned *);			/* (TSF) */
 #endif
 #if __POSIX_VISIBLE >= 200112
-int	 posix_memalign(void **, size_t, size_t) __nonnull(1)
+int	 posix_memalign(void **, size_t, size_t) __nonnull(1) __alloc_align(2)
 	    __alloc_size(3);			/* (ADV) */
 int	 setenv(const char *, const char *, int);
 int	 unsetenv(const char *);
diff --git a/sys/sys/malloc.h b/sys/sys/malloc.h
index 6b8a9c0..c09d749 100644
--- a/sys/sys/malloc.h
+++ b/sys/sys/malloc.h
@@ -174,7 +174,7 @@ void	contigfree(void *addr, unsigned long size, struct malloc_type *type);
 void	*contigmalloc(unsigned long size, struct malloc_type *type, int flags,
 	    vm_paddr_t low, vm_paddr_t high, unsigned long alignment,
 	    vm_paddr_t boundary) __malloc_like __result_use_check
-	    __alloc_size(1);
+	    __alloc_size(1) __alloc_align(6);
 void	free(void *addr, struct malloc_type *type);
 void	*malloc(unsigned long size, struct malloc_type *type, int flags)
 	    __malloc_like __result_use_check __alloc_size(1);