diff options
Diffstat (limited to 'lib/libc/stdlib/malloc.3')
| -rw-r--r-- | lib/libc/stdlib/malloc.3 | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/lib/libc/stdlib/malloc.3 b/lib/libc/stdlib/malloc.3 index 35222a15cee..c1776f61cb8 100644 --- a/lib/libc/stdlib/malloc.3 +++ b/lib/libc/stdlib/malloc.3 @@ -30,9 +30,9 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.\" $OpenBSD: malloc.3,v 1.118 2018/11/08 05:58:21 otto Exp $ +.\" $OpenBSD: malloc.3,v 1.119 2018/11/18 16:15:18 otto Exp $ .\" -.Dd $Mdocdate: November 8 2018 $ +.Dd $Mdocdate: November 18 2018 $ .Dt MALLOC 3 .Os .Sh NAME @@ -43,7 +43,8 @@ .Nm reallocarray , .Nm recallocarray , .Nm freezero , -.Nm aligned_alloc +.Nm aligned_alloc , +.Nm malloc_usable_size .Nd memory allocation and deallocation .Sh SYNOPSIS .In stdlib.h @@ -63,6 +64,8 @@ .Fn freezero "void *ptr" "size_t size" .Ft void * .Fn aligned_alloc "size_t alignment" "size_t size" +.Ft size_t +.Fn malloc_usable_size "void *ptr" .Vt char *malloc_options ; .Sh DESCRIPTION The standard functions @@ -191,7 +194,7 @@ must be a value such that .Fa size is the size of the earlier allocation that returned .Fa ptr , -otherwise the behaviour is undefined. +otherwise the behavior is undefined. .Pp The .Fn freezero @@ -233,6 +236,25 @@ If is not a multiple of .Fa alignment , behavior is undefined. +.Pp +The +.Fn malloc_usable_size +function returns the actual size of the allocated memory pointed to by +.Va ptr . +If +.Va ptr +is +.Dv NULL , +it returns 0. +If +.Va ptr +was never returned by an allocation function or freed before, +the behavior is undefined. +This function should not be relied upon since it exposes some of the internal +workings of the +.Fn malloc +family of functions. +Writing beyond the requested size introduces undefined behavior. .Sh RETURN VALUES Upon successful completion, the allocation functions return a pointer to the allocated space; otherwise, @@ -618,7 +640,9 @@ function appeared in .Ox 6.2 . The .Fn aligned_alloc -function appeared in +and +.Fn malloc_usable_size +functions appeared in .Ox 6.5 . .Sh CAVEATS When using |