Re: [patch v5] aligned_alloc: conform to C17

[Carlos O'Donell <carlos@redhat.com>]

On 5/2/23 15:01, DJ Delorie wrote:
> 
> Changes as requested...
> 

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> From a2c1315544c72dedfcbd94b2efa7afb3eb1f0a02 Mon Sep 17 00:00:00 2001
> From: DJ Delorie <dj@redhat.com>
> Date: Tue, 21 Mar 2023 00:46:43 -0400
> Subject: aligned_alloc: conform to C17
> 
> This patch adds the strict checking for power-of-two alignments
> in aligned_alloc(), and updates the manual accordingly.
> 
> diff --git a/malloc/Makefile b/malloc/Makefile
> index f4cae2538c..57a9677512 100644
> --- a/malloc/Makefile
> +++ b/malloc/Makefile
> @@ -44,11 +44,13 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
>  	 tst-safe-linking \
>  	 tst-mallocalign1 \
>  	 tst-memalign-2 \
> -	 tst-memalign-3
> +	 tst-memalign-3 \
> +	 tst-aligned-alloc

OK.

>  
>  tests-static := \
>  	 tst-interpose-static-nothread \
> -	 tst-interpose-static-thread
> +	 tst-interpose-static-thread \
> +	 tst-aligned-alloc-static

OK.

>  
>  # Test for the malloc_set_state symbol removed in glibc 2.25.
>  ifeq ($(have-GLIBC_2.23)$(build-shared),yesyes)
> diff --git a/malloc/malloc-debug.c b/malloc/malloc-debug.c
> index 3867d15698..da9d2340d3 100644
> --- a/malloc/malloc-debug.c
> +++ b/malloc/malloc-debug.c
> @@ -299,7 +299,14 @@ __debug_memalign (size_t alignment, size_t bytes)
>    return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
>  }
>  strong_alias (__debug_memalign, memalign)
> -strong_alias (__debug_memalign, aligned_alloc)
> +static void *
> +__debug_aligned_alloc (size_t alignment, size_t bytes)
> +{
> +  if (!powerof2 (alignment) || alignment == 0)
> +    return NULL;
> +  return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
> +}
> +strong_alias (__debug_aligned_alloc, aligned_alloc)

OK.

>  
>  static void *
>  __debug_pvalloc (size_t bytes)
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index e33ed665db..5d8b61d66c 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -3528,6 +3528,29 @@ __libc_memalign (size_t alignment, size_t bytes)
>    void *address = RETURN_ADDRESS (0);
>    return _mid_memalign (alignment, bytes, address);
>  }
> +libc_hidden_def (__libc_memalign)
> +
> +/* For ISO C17.  */

OK. Corrected.

> +void *
> +weak_function
> +aligned_alloc (size_t alignment, size_t bytes)
> +{
> +  if (!__malloc_initialized)
> +    ptmalloc_init ();
> +
> +/* Similar to memalign, but starting with ISO C17 the standard
> +   requires an error for alignments that are not supported by the
> +   implementation.  Valid alignments for the current implementation
> +   are non-negative powers of two.  */

OK.

> +  if (!powerof2 (alignment) || alignment == 0)
> +    {
> +      __set_errno (EINVAL);
> +      return 0;
> +    }
> +
> +  void *address = RETURN_ADDRESS (0);
> +  return _mid_memalign (alignment, bytes, address);
> +}
>  
>  static void *
>  _mid_memalign (size_t alignment, size_t bytes, void *address)
> @@ -3618,9 +3641,6 @@ _mid_memalign (size_t alignment, size_t bytes, void *address)
>            ar_ptr == arena_for_chunk (mem2chunk (p)));
>    return tag_new_usable (p);
>  }
> -/* For ISO C11.  */
> -weak_alias (__libc_memalign, aligned_alloc)
> -libc_hidden_def (__libc_memalign)
>  
>  void *
>  __libc_valloc (size_t bytes)
> diff --git a/malloc/tst-aligned-alloc-static.c b/malloc/tst-aligned-alloc-static.c
> new file mode 100644
> index 0000000000..d504473094
> --- /dev/null
> +++ b/malloc/tst-aligned-alloc-static.c
> @@ -0,0 +1 @@
> +#include "tst-aligned-alloc.c"
> diff --git a/malloc/tst-aligned-alloc.c b/malloc/tst-aligned-alloc.c
> new file mode 100644
> index 0000000000..8bd6527147
> --- /dev/null
> +++ b/malloc/tst-aligned-alloc.c
> @@ -0,0 +1,80 @@
> +/* Test for C17 alignment requirements.

OK. Corrected.

> +   Copyright (C) 2023 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <errno.h>
> +#include <malloc.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <libc-diag.h>
> +#include <support/check.h>
> +
> +static int
> +do_test (void)
> +{
> +  void *p1;
> +  void *p2;
> +  void *p3;
> +  void *p4;
> +  void *p5;
> +
> +  errno = 0;
> +
> +  /* The implementation supports alignments that are non-negative powers of 2.
> +     We test 5 distinct conditions here:
> +     - A non-negative power of 2 alignment e.g. 64.
> +     - A degenerate zero power of 2 alignment e.g. 1.
> +     - A non-power-of-2 alignment e.g. 65.
> +     - A zero alignment.
> +     - A corner case SIZE_MAX / 2 + 1 alignment.
> +  */
> +
> +  p1 = aligned_alloc (64, 64);
> +
> +  if (p1 == NULL)
> +    FAIL_EXIT1 ("aligned_alloc(64, 64) failed");
> +
> +  p2 = aligned_alloc (1, 64);
> +
> +  if (p2 == NULL)
> +    FAIL_EXIT1 ("aligned_alloc(1, 64) failed");
> +
> +  p3 = aligned_alloc (65, 64);
> +
> +  if (p3 != NULL)
> +    FAIL_EXIT1 ("aligned_alloc(65, 64) did not fail");
> +
> +  p4 = aligned_alloc (0, 64);
> +
> +  if (p4 != NULL)
> +    FAIL_EXIT1 ("aligned_alloc(0, 64) did not fail");
> +
> +  /* This is an alignment like 0x80000000...UL */
> +  p5 = aligned_alloc (SIZE_MAX / 2 + 1, 64);
> +
> +  if (p5 != NULL)
> +    FAIL_EXIT1 ("aligned_alloc(SIZE_MAX/2+1, 64) did not fail");
> +
> +  free (p1);
> +  free (p2);
> +  return 0;
> +}
> +
> +#define TEST_FUNCTION do_test ()
> +#include "../test-skeleton.c"
> diff --git a/manual/memory.texi b/manual/memory.texi
> index 9d3398a326..8952ff2bfa 100644
> --- a/manual/memory.texi
> +++ b/manual/memory.texi
> @@ -995,7 +995,7 @@ power of two than that, use @code{aligned_alloc} or @code{posix_memalign}.
>  @c Alias to memalign.
>  The @code{aligned_alloc} function allocates a block of @var{size} bytes whose
>  address is a multiple of @var{alignment}.  The @var{alignment} must be a
> -power of two and @var{size} must be a multiple of @var{alignment}.
> +power of two.
>  
>  The @code{aligned_alloc} function returns a null pointer on error and sets
>  @code{errno} to one of the following values:
> 

-- 
Cheers,
Carlos.