libc: Add free_sized() and free_aligned_sized() as per C23

Add C23 sized deallocation entry points as thin wrappers around free(3).
Implementations may ignore size and alignment hints, so behaviour stays
correct for existing allocations without validating caller metadata yet.

When jemalloc is updated to 5.3.1, rewire these to je_free_sized() and
je_free_aligned_sized() so deallocation can use the allocator's sized
deallocation (free_sized for fast paths and free_aligned_sized for
correct aligned hints.)

Please note this change satisfies the standard interface only. Both
functions should be delegated to jemalloc after the upgrade so callers
get the intended allocator behaviour; until then, hints are unused and
neither sized nor aligned-sized deallocation optimizations apply.

Signed-off-by:	Faraz Vahedi <kfv@kfv.io>
Reviewed by:	fuz
Pull Request:	https://github.com/freebsd/freebsd-src/pull/2201
MFC after:	1 month

include/stdlib.h

@@ -173,6 +173,8 @@ _Noreturn void
  */
 #if __ISO_C_VISIBLE >= 2023
 size_t	memalignment(const void *) __pure2;
+void	free_sized(void *, size_t) __noexcept;
+void	free_aligned_sized(void *, size_t, size_t) __noexcept;
 #endif /* __ISO_C_VISIBLE >= 2023 */
 
 /*

lib/libc/stdlib/malloc/Makefile.inc

@@ -1,3 +1,12 @@
 SYM_MAPS+=${LIBC_SRCTOP}/stdlib/malloc/Symbol.map
 
+.PATH: ${LIBC_SRCTOP}/stdlib/malloc
+
+MISRCS+=	free_aligned_sized.c \
+		free_sized.c
+
+MAN+=		free_sized.3
+
+MLINKS+=	free_sized.3 free_aligned_sized.3
+
 .include "${LIBC_SRCTOP}/stdlib/malloc/${OPT_LIBC_MALLOC}/Makefile.inc"

lib/libc/stdlib/malloc/Symbol.map

@@ -47,6 +47,13 @@ FBSD_1.4 {
 	__mallctlbymib;
 };
 
+FBSD_1.9 {
+	free_sized;
+	free_aligned_sized;
+	__free_sized;
+	__free_aligned_sized;
+};
+
 FBSDprivate_1.0 {
 	_malloc_thread_cleanup;
 	_malloc_prefork;

lib/libc/stdlib/malloc/free_aligned_sized.c

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2026 Faraz Vahedi <kfv@kfv.io>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/cdefs.h>
+#include <stdlib.h>
+
+void	__free(void *);
+
+void
+__free_aligned_sized(void *ptr, size_t alignment, size_t size)
+{
+
+	(void)alignment;
+	(void)size;
+	__free(ptr);
+}
+
+__weak_reference(__free_aligned_sized, free_aligned_sized);

lib/libc/stdlib/malloc/free_sized.3

@@ -0,0 +1,100 @@
+.\"
+.\" Copyright (c) 2026 Faraz Vahedi <kfv@kfv.io>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd May 17, 2026
+.Dt FREE_SIZED 3
+.Os
+.Sh NAME
+.Nm free_sized ,
+.Nm free_aligned_sized
+.Nd C23 sized deallocation functions
+.Sh SYNOPSIS
+.Lb libc
+.In stdlib.h
+.Ft void
+.Fn free_sized "void *ptr" "size_t size"
+.Ft void
+.Fn free_aligned_sized "void *ptr" "size_t alignment" "size_t size"
+.Sh DESCRIPTION
+The
+.Fn free_sized
+function deallocates the memory referenced by
+.Fa ptr
+that was previously allocated by
+.Xr malloc 3 ,
+.Xr realloc 3 ,
+or
+.Xr calloc 3 .
+The
+.Fa size
+argument shall equal the size passed to the allocation function.
+The result of an
+.Xr aligned_alloc 3
+may not be passed to
+.Fn free_sized .
+.Pp
+The
+.Fn free_aligned_sized
+function deallocates memory referenced by
+.Fa ptr
+that was previously allocated by
+.Xr aligned_alloc 3 .
+The
+.Fa alignment
+and
+.Fa size
+arguments shall equal the values supplied to the allocation function.
+The result of an
+.Xr malloc 3 ,
+.Xr calloc 3 ,
+or
+.Xr realloc 3
+may not be passed to
+.Fn free_aligned_sized .
+.Pp
+If
+.Fa ptr
+is neither a null pointer nor a pointer returned by the allocation functions
+described above for the corresponding deallocation function, the behaviour is
+undefined, and so is supplying a
+.Fa size
+or
+.Fa alignment
+that does not match the original allocation.
+.Sh IMPLEMENTATION NOTES
+The C standard permits an implementation to ignore the
+.Fa size
+and
+.Fa alignment
+hints.
+The current implementation forwards to
+.Xr free 3
+without validating these arguments, so behaviour remains correct for
+well-formed use.
+.Pp
+These functions will be wired to the system allocator's sized deallocation,
+once supported, as with the rest of the memory allocation API, so that
+.Fa size
+and
+.Fa alignment
+hints are used for performance and security benefits.
+That behaviour conforms to the practice recommended for each function in the
+C standard.
+.Sh SEE ALSO
+.Xr free 3 ,
+.Xr malloc 3 ,
+.Xr calloc 3 ,
+.Xr realloc 3 ,
+.Xr aligned_alloc 3 ,
+.Xr jemalloc 3
+.Sh STANDARDS
+The
+.Fn free_sized
+and
+.Fn free_aligned_sized
+functions conform to
+.St -isoC-2023 .
+.Sh AUTHOR
+.An Faraz Vahedi Aq Mt kfv@kfv.io

lib/libc/stdlib/malloc/free_sized.c

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2026 Faraz Vahedi <kfv@kfv.io>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/cdefs.h>
+#include <stdlib.h>
+
+void	__free(void *);
+
+void
+__free_sized(void *ptr, size_t size)
+{
+
+	(void)size;
+	__free(ptr);
+}
+
+__weak_reference(__free_sized, free_sized);

lib/libc/stdlib/memory.3

@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd October 18, 2023
+.Dd May 17, 2026
 .Dt MEMORY 3
 .Os
 .Sh NAME
@@ -33,6 +33,8 @@
 .Nm alloca ,
 .Nm calloc ,
 .Nm free ,
+.Nm free_sized ,
+.Nm free_aligned_sized ,
 .Nm malloc ,
 .Nm posix_memalign ,
 .Nm realloc ,
@@ -53,6 +55,10 @@
 .Fn calloc "size_t nelem" "size_t elsize"
 .Ft void
 .Fn free "void *ptr"
+.Ft void
+.Fn free_sized "void *ptr" "size_t size"
+.Ft void
+.Fn free_aligned_sized "void *ptr" "size_t alignment" "size_t size"
 .Ft void *
 .Fn malloc "size_t size"
 .Ft int
@@ -79,6 +85,8 @@ individual manual pages.
 .Xr alloca 3 ,
 .Xr calloc 3 ,
 .Xr free 3 ,
+.Xr free_aligned_sized 3 ,
+.Xr free_sized 3 ,
 .Xr malloc 3 ,
 .Xr posix_memalign 3 ,
 .Xr realloc 3 ,
@@ -101,3 +109,10 @@ and
 .Fn posix_memalign
 functions conform to
 .St -p1003.1-2001 .
+.Pp
+The
+.Fn free_sized
+and
+.Fn free_aligned_sized
+functions conform to
+.St -isoC-2023 .