[06/25] Add struct scratch_buffer and its internal helper functions
diff mbox

Message ID 551D8AE1.5000805@redhat.com
State New
Headers show

Commit Message

Florian Weimer April 2, 2015, 6:30 p.m. UTC
On 04/01/2015 06:28 PM, Florian Weimer wrote:
> On 03/23/2015 07:48 PM, Florian Weimer wrote:
>> On 03/23/2015 07:46 PM, Joseph Myers wrote:
>>> On Mon, 23 Mar 2015, Florian Weimer wrote:
>>>
>>>> On 03/23/2015 07:41 PM, Joseph Myers wrote:
>>>>
>>>>>> Since C allows platforms where pointers and/or floating-point values have
>>>>>> alignments stricter than intmax_t, I suggest using 'max (__alignof__
>>>>>> (intmax_t), __alignof__ (max_align_t))' along with a comment explaining why
>>>>>> you don't trust max_align_t here.
>>>>>
>>>>> max_align_t was added to stddef.h in GCC 4.7, so we can't rely on it in 
>>>>> glibc without appropriate conditionals.
>>>>
>>>> We compile glibc in -std=gnu99 mode, and max_align_t appears available.
>>>>  Suggestions?
>>>
>>> It's specifically when compiling with GCC 4.6 (the oldest supported 
>>> version) that it won't be available.
>>
>> Oh, I misread what you wrote.  What I was saying is that we can't get it
>> easily with GCC 4.9.2, either.
> 
> I proposed a patch for a libc_max_align_t type here:
> 
>   <https://sourceware.org/ml/libc-alpha/2015-04/msg00004.html>
> 
> As far as I can see, using that instead of intmax_t should address the
> only remaining issue with this patch.

And here is this patch, with libc_max_align_t.

	* include/scratch_buffer.h: New file.
	* malloc/scratch_buffer_grow.c: Likewise.
	* malloc/scratch_buffer_grow_preserve.c: Likewise.
	* malloc/scratch_buffer_set_array_size.c: Likewise.
	* malloc/tst-scratch_buffer.c: Likewise.
	* malloc/Makefile (routines): Add scratch_buffer_grow.
	(tests): Add test case.
	* malloc/Versions (GLIBC_PRIVATE): Export
	__libc_scratch_buffer_grow, __libc_scratch_buffer_grow_preserve,
	__libc_scratch_buffer_set_array_size.

Comments

Paul Eggert April 3, 2015, 1:12 a.m. UTC | #1
On 04/02/2015 11:30 AM, Florian Weimer wrote:
> +static inline void
> +scratch_buffer_init (struct scratch_buffer *buffer)
> +  __attribute__ ((always_inline));
> +static inline void

This should be just "static __always_inline void"; there should be no 
need to have both decl and defn, and __always_inline arranges for both 
'inline' and the attribute.

But then again, why bother to declare this function to be inline? Isn't 
the compiler smart enough to inline when needed?  I assume that this 
include file is not visible to the user, so is there some reason to 
require the function to be __always_inline, or even __inline?

Similarly for the other functions in this header -- why bother to 
declare them to be inline?  Can't the compiler figure it out?  Why is it 
relevant to the ABI whether the functions are inlined, if the header is 
not user-visible?  These functions are all private to glibc, right?
> +  /* Discard old buffer.  */
> +  scratch_buffer_free (buffer);
> +
> +  /* Check for overflow.  */
> +  if (__glibc_unlikely (new_length < buffer->length))
> +    {
> +      /* Buffer must remain valid to free.  */
> +      scratch_buffer_init (buffer);
> +      __set_errno (ENOMEM);
> +      return false;
> +    }
> +
> +  void *new_ptr = malloc (new_length);
> +  if (new_ptr == NULL)
> +    {
> +      /* Buffer must remain valid to free.  */
> +      scratch_buffer_init (buffer);
> +      return false;
> +    }

The two ifs can be combined so that there's only copy of the cleanup 
code.  Also, if all that's needed is that the buffer remains valid to 
free, why not let the caller's free (which we need anyway) do the 
cleanup rather than doing the cleanup redundantly ourselves? Instead of 
the above 19 lines, we could have just 6 lines:

  void *new_ptr = new_length < buffer->length ? NULL : malloc (new_length);
  if (__glibc_unlikely (! new_ptr))
    {
       __set_errno (ENOMEM);
       return false;
    }

Similarly for __libc_scratch_buffer_grow_preserve and for 
__libc_scratch_buffer_set_array_size.  The latter fix will fix the 
problem that when __libc_scratch_buffer_grow_preserve fails, sometimes 
it reinitializes the buffer to be empty and sometimes it doesn't, which 
is inconsistent.

> +	 buffer->length describes a small buffer on the stack.  We use
> +	 buffer->length instead of sizeof (buffer->__space) to avoid
> +	 making the size of struct scratch_buffer part of the ABI. */

Sorry, I still don't get why the ABI matters here, since the functions 
are all private and presumably are all linked into glibc already.

Patch
diff mbox

From 4cd368c815d1b3265bba3fce6eb08a2e1d2a6ccf Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Thu, 2 Apr 2015 20:20:06 +0200
Subject: [PATCH] Add struct scratch_buffer and its internal helper functions

These will be used from NSS modules, so they have to be exported.
---
 include/scratch_buffer.h               | 144 ++++++++++++++++++++++++++++++
 malloc/Makefile                        |   6 +-
 malloc/Versions                        |   5 ++
 malloc/scratch_buffer_grow.c           |  52 +++++++++++
 malloc/scratch_buffer_grow_preserve.c  |  65 ++++++++++++++
 malloc/scratch_buffer_set_array_size.c |  60 +++++++++++++
 malloc/tst-scratch_buffer.c            | 155 +++++++++++++++++++++++++++++++++
 7 files changed, 485 insertions(+), 2 deletions(-)
 create mode 100644 include/scratch_buffer.h
 create mode 100644 malloc/scratch_buffer_grow.c
 create mode 100644 malloc/scratch_buffer_grow_preserve.c
 create mode 100644 malloc/scratch_buffer_set_array_size.c
 create mode 100644 malloc/tst-scratch_buffer.c

diff --git a/include/scratch_buffer.h b/include/scratch_buffer.h
new file mode 100644
index 0000000..bcb0d6b
--- /dev/null
+++ b/include/scratch_buffer.h
@@ -0,0 +1,144 @@ 
+/* Variable-sized buffer with on-stack default allocation.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _SCRATCH_BUFFER_H
+#define _SCRATCH_BUFFER_H
+
+/* Scratch buffers with a default stack allocation and fallback to
+   heap allocation.  It is expected that this function is used in this
+   way:
+
+     struct scratch_buffer tmpbuf;
+     scratch_buffer_init (&tmpbuf);
+
+     while (!function_that_uses_buffer (tmpbuf.data, tmpbuf.length))
+       if (!scratch_buffer_grow (&tmpbuf))
+	 return -1;
+
+     scratch_buffer_free (&tmpbuf);
+     return 0;
+
+   The allocation functions (scratch_buffer_grow,
+   scratch_buffer_grow_preserve, scratch_buffer_set_array_size) make
+   sure that the heap allocation, if any, is freed, so that the code
+   above does not have a memory leak.  The buffer still remains in a
+   state that can be deallocated using scratch_buffer_free, so a loop
+   like this is valid as well:
+
+     struct scratch_buffer tmpbuf;
+     scratch_buffer_init (&tmpbuf);
+
+     while (!function_that_uses_buffer (tmpbuf.data, tmpbuf.length))
+       if (!scratch_buffer_grow (&tmpbuf))
+	 break;
+
+     scratch_buffer_free (&tmpbuf);
+
+   The non-inlined functions are implemented in such a way that it is
+   possible to change the size of the pre-allocated buffer without
+   impacting ABI.
+
+   scratch_buffer_grow and scratch_buffer_grow_preserve are guaranteed
+   to grow the buffer by at least 512 bytes.  This means that when
+   using the scratch buffer as a backing store for a non-character
+   array whose element size, in bytes, is 512 or smaller, the scratch
+   buffer only has to grow once to make room for at least one more
+   element.
+*/
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include <libc-internal.h>
+
+/* Scratch buffer.  Must be initialized with scratch_buffer_init
+   before its use.  */
+struct scratch_buffer {
+  void *data;    /* Pointer to the beginning of the scratch area.  */
+  size_t length; /* Allocated space at the data pointer, in bytes.  */
+  char __space[1024]
+    __attribute__ ((aligned (__alignof__ (libc_max_align_t))));
+};
+
+/* Initializes *BUFFER so that BUFFER->data points to BUFFER->__space
+   and BUFFER->length reflects the available space.  */
+static inline void
+scratch_buffer_init (struct scratch_buffer *buffer)
+  __attribute__ ((always_inline));
+static inline void
+scratch_buffer_init (struct scratch_buffer *buffer)
+{
+  buffer->data = buffer->__space;
+  buffer->length = sizeof (buffer->__space);
+}
+
+/* Deallocates *BUFFER (if it was heap-allocated).  */
+static inline void
+scratch_buffer_free (struct scratch_buffer *buffer)
+{
+  if (buffer->data != buffer->__space)
+    free (buffer->data);
+}
+
+/* Grow *BUFFER by some arbitrary amount.  The buffer contents is NOT
+   preserved.  Return true on success, false on allocation failure (in
+   which case the old buffer is freed).  On success, the new buffer is
+   larger than the previous size.  On failure, *BUFFER is deallocated,
+   but remains in a free-able state, and errno is set.  */
+bool __libc_scratch_buffer_grow (struct scratch_buffer *buffer);
+libc_hidden_proto (__libc_scratch_buffer_grow)
+
+/* Alias for __libc_scratch_buffer_grow.  */
+static inline bool
+scratch_buffer_grow (struct scratch_buffer *buffer)
+{
+  return __glibc_likely (__libc_scratch_buffer_grow (buffer));
+}
+
+/* Like __libc_scratch_buffer_grow, but preserve the old buffer
+   contents on success, as a prefix of the new buffer.  */
+bool __libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer);
+libc_hidden_proto (__libc_scratch_buffer_grow_preserve)
+
+/* Alias for __libc_scratch_buffer_grow_preserve.  */
+static inline bool
+scratch_buffer_grow_preserve (struct scratch_buffer *buffer)
+{
+  return __glibc_likely (__libc_scratch_buffer_grow_preserve (buffer));
+}
+
+/* Grow *BUFFER so that it can store at least NELEM elements of SIZE
+   bytes.  The buffer contents are NOT preserved.  Both NELEM and SIZE
+   can be zero.  Return true on success, false on allocation failure
+   (in which case the old buffer is freed, but *BUFFER remains in a
+   free-able state, and errno is set).  It is unspecified whether this
+   function can reduce the array size.  */
+bool __libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer,
+					   size_t nelem, size_t size);
+libc_hidden_proto (__libc_scratch_buffer_set_array_size)
+
+/* Alias for __libc_scratch_set_array_size.  */
+static inline bool
+scratch_buffer_set_array_size (struct scratch_buffer *buffer,
+			       size_t nelem, size_t size)
+{
+  return __glibc_likely (__libc_scratch_buffer_set_array_size
+			 (buffer, nelem, size));
+}
+
+#endif /* _SCRATCH_BUFFER_H */
diff --git a/malloc/Makefile b/malloc/Makefile
index 5f68a79..9e7112a 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -27,10 +27,12 @@  headers := $(dist-headers) obstack.h mcheck.h
 tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
 	 tst-mallocstate tst-mcheck tst-mallocfork tst-trim1 \
 	 tst-malloc-usable tst-realloc tst-posix_memalign \
-	 tst-pvalloc tst-memalign tst-mallopt
+	 tst-pvalloc tst-memalign tst-mallopt tst-scratch_buffer
 test-srcs = tst-mtrace
 
-routines = malloc morecore mcheck mtrace obstack
+routines = malloc morecore mcheck mtrace obstack \
+  scratch_buffer_grow scratch_buffer_grow_preserve \
+  scratch_buffer_set_array_size
 
 install-lib := libmcheck.a
 non-lib.a := libmcheck.a
diff --git a/malloc/Versions b/malloc/Versions
index 7ca9bdf..f3c3d8a 100644
--- a/malloc/Versions
+++ b/malloc/Versions
@@ -67,5 +67,10 @@  libc {
 
     # Internal destructor hook for libpthread.
     __libc_thread_freeres;
+
+    # struct scratch_buffer support
+    __libc_scratch_buffer_grow;
+    __libc_scratch_buffer_grow_preserve;
+    __libc_scratch_buffer_set_array_size;
   }
 }
diff --git a/malloc/scratch_buffer_grow.c b/malloc/scratch_buffer_grow.c
new file mode 100644
index 0000000..6621393
--- /dev/null
+++ b/malloc/scratch_buffer_grow.c
@@ -0,0 +1,52 @@ 
+/* Variable-sized buffer with on-stack default allocation.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <scratch_buffer.h>
+#include <errno.h>
+
+bool
+__libc_scratch_buffer_grow (struct scratch_buffer *buffer)
+{
+  size_t new_length = buffer->length * 2;
+
+  /* Discard old buffer.  */
+  scratch_buffer_free (buffer);
+
+  /* Check for overflow.  */
+  if (__glibc_unlikely (new_length < buffer->length))
+    {
+      /* Buffer must remain valid to free.  */
+      scratch_buffer_init (buffer);
+      __set_errno (ENOMEM);
+      return false;
+    }
+
+  void *new_ptr = malloc (new_length);
+  if (new_ptr == NULL)
+    {
+      /* Buffer must remain valid to free.  */
+      scratch_buffer_init (buffer);
+      return false;
+    }
+
+  /* Install new heap-based buffer.  */
+  buffer->data = new_ptr;
+  buffer->length = new_length;
+  return true;
+}
+libc_hidden_def (__libc_scratch_buffer_grow);
diff --git a/malloc/scratch_buffer_grow_preserve.c b/malloc/scratch_buffer_grow_preserve.c
new file mode 100644
index 0000000..3abbd56
--- /dev/null
+++ b/malloc/scratch_buffer_grow_preserve.c
@@ -0,0 +1,65 @@ 
+/* Variable-sized buffer with on-stack default allocation.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <scratch_buffer.h>
+#include <errno.h>
+
+bool
+__libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer)
+{
+  size_t new_length = 2 * buffer->length;
+  void *new_ptr;
+
+  if (buffer->data == buffer->__space)
+    {
+      /* Move buffer to the heap.  No overflow is possible because
+	 buffer->length describes a small buffer on the stack.  We use
+	 buffer->length instead of sizeof (buffer->__space) to avoid
+	 making the size of struct scratch_buffer part of the ABI. */
+      new_ptr = malloc (new_length);
+      if (new_ptr == NULL)
+	return false;
+      memcpy (new_ptr, buffer->__space, buffer->length);
+    }
+  else
+    {
+      /* Buffer was already on the heap.  Check for overflow.  */
+      if (__glibc_unlikely (new_length < buffer->length))
+	{
+	  /* Deallocate, but buffer must remain valid to free.  */
+	  free (buffer->data);
+	  scratch_buffer_init (buffer);
+	  __set_errno (ENOMEM);
+	  return false;
+	}
+      new_ptr = realloc (buffer->data, new_length);
+      if (new_ptr == NULL)
+	{
+	  /* Deallocate, but buffer must remain valid to free.  */
+	  free (buffer->data);
+	  scratch_buffer_init (buffer);
+	  return false;
+	}
+    }
+
+  /* Install new heap-based buffer.  */
+  buffer->data = new_ptr;
+  buffer->length = new_length;
+  return true;
+}
+libc_hidden_def (__libc_scratch_buffer_grow_preserve);
diff --git a/malloc/scratch_buffer_set_array_size.c b/malloc/scratch_buffer_set_array_size.c
new file mode 100644
index 0000000..6e7a7e9
--- /dev/null
+++ b/malloc/scratch_buffer_set_array_size.c
@@ -0,0 +1,60 @@ 
+/* Variable-sized buffer with on-stack default allocation.
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <scratch_buffer.h>
+#include <errno.h>
+
+bool
+__libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer,
+				      size_t nelem, size_t size)
+{
+  /* Avoid overflow check if both values are small. */
+  if ((nelem | size) >> (sizeof (size_t) * CHAR_BIT / 2) != 0)
+    {
+      if (nelem != 0 && size > SIZE_MAX / nelem)
+	{
+	  /* Overflow.  Discard the old buffer, but it must remain
+	     valid to free.  */
+	  scratch_buffer_free (buffer);
+	  scratch_buffer_init (buffer);
+	  __set_errno (ENOMEM);
+	  return false;
+	}
+    }
+
+  size_t new_length = nelem * size;
+  if (new_length <= buffer->length)
+    return true;
+
+  /* Discard old buffer.  */
+  scratch_buffer_free (buffer);
+
+  char *new_ptr = malloc (new_length);
+  if (new_ptr == NULL)
+    {
+      /* Buffer must remain valid to free.  */
+      scratch_buffer_init (buffer);
+      return false;
+    }
+
+  /* Install new heap-based buffer.  */
+  buffer->data = new_ptr;
+  buffer->length = new_length;
+  return true;
+}
+libc_hidden_def (__libc_scratch_buffer_set_array_size);
diff --git a/malloc/tst-scratch_buffer.c b/malloc/tst-scratch_buffer.c
new file mode 100644
index 0000000..dcae512
--- /dev/null
+++ b/malloc/tst-scratch_buffer.c
@@ -0,0 +1,155 @@ 
+/*
+   Copyright (C) 2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <scratch_buffer.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+static bool
+unchanged_array_size (struct scratch_buffer *buf, size_t a, size_t b)
+{
+  size_t old_length = buf->length;
+  if (!scratch_buffer_set_array_size (buf, a, b))
+    {
+      printf ("scratch_buffer_set_array_size failed: %zu %zu\n",
+	      a, b);
+      return false;
+    }
+  if (old_length != buf->length)
+    {
+      printf ("scratch_buffer_set_array_size did not preserve size: %zu %zu\n",
+	      a, b);
+      return false;
+    }
+  return true;
+}
+
+static bool
+array_size_must_fail (size_t a, size_t b)
+{
+  for (int pass = 0; pass < 2; ++pass)
+    {
+      struct scratch_buffer buf;
+      scratch_buffer_init (&buf);
+      if (pass > 0)
+	if (!scratch_buffer_grow (&buf))
+	  {
+	    printf ("scratch_buffer_grow in array_size_must_fail failed\n");
+	    return false;
+	  }
+      if (scratch_buffer_set_array_size (&buf, a, b))
+	{
+	  printf ("scratch_buffer_set_array_size passed: %d %zu %zu\n",
+		  pass, a, b);
+	  return false;
+	}
+      if (buf.data != buf.__space)
+	{
+	  printf ("scratch_buffer_set_array_size did not free: %d %zu %zu\n",
+		  pass, a, b);
+	  return false;
+	}
+    }
+  return true;
+}
+
+static int
+do_test (void)
+{
+  {
+    struct scratch_buffer buf;
+    scratch_buffer_init (&buf);
+    memset (buf.data, ' ', buf.length);
+    scratch_buffer_free (&buf);
+  }
+  {
+    struct scratch_buffer buf;
+    scratch_buffer_init (&buf);
+    memset (buf.data, ' ', buf.length);
+    size_t old_length = buf.length;
+    scratch_buffer_grow (&buf);
+    if (buf.length <= old_length)
+      {
+	printf ("scratch_buffer_grow did not enlarge buffer\n");
+	return 1;
+      }
+    memset (buf.data, ' ', buf.length);
+    scratch_buffer_free (&buf);
+  }
+  {
+    struct scratch_buffer buf;
+    scratch_buffer_init (&buf);
+    memset (buf.data, '@', buf.length);
+    strcpy (buf.data, "prefix");
+    size_t old_length = buf.length;
+    scratch_buffer_grow_preserve (&buf);
+    if (buf.length <= old_length)
+      {
+	printf ("scratch_buffer_grow_preserve did not enlarge buffer\n");
+	return 1;
+      }
+    if (strcmp (buf.data, "prefix") != 0)
+      {
+	printf ("scratch_buffer_grow_preserve did not copy buffer\n");
+	return 1;
+      }
+    for (unsigned i = 7; i < old_length; ++i)
+      if (((char *)buf.data)[i] != '@')
+	{
+	  printf ("scratch_buffer_grow_preserve did not copy buffer (%u)\n",
+		  i);
+	  return 1;
+	}
+    scratch_buffer_free (&buf);
+  }
+  {
+    struct scratch_buffer buf;
+    scratch_buffer_init (&buf);
+    for (int pass = 0; pass < 4; ++pass)
+      {
+	if (!(unchanged_array_size (&buf, 0, 0)
+	      && unchanged_array_size (&buf, 1, 0)
+	      && unchanged_array_size (&buf, 0, 1)
+	      && unchanged_array_size (&buf, -1, 0)
+	      && unchanged_array_size (&buf, 0, -1)
+	      && unchanged_array_size (&buf, 1ULL << 16, 0)
+	      && unchanged_array_size (&buf, 0, 1ULL << 16)
+	      && unchanged_array_size (&buf, 1ULL << 32, 0)
+	      && unchanged_array_size (&buf, 0, 1ULL << 32)))
+	  return 1;
+	if (!scratch_buffer_grow (&buf))
+	  {
+	    printf ("scratch_buffer_grow_failed (pass %d)\n", pass);
+	  }
+      }
+    scratch_buffer_free (&buf);
+  }
+  {
+    if (!(array_size_must_fail (-1, 1)
+	  && array_size_must_fail (-1, -1)
+	  && array_size_must_fail (1, -1)
+	  && array_size_must_fail (((size_t)-1) / 4, 4)
+	  && array_size_must_fail (4, ((size_t)-1) / 4)))
+	return 1;
+  }
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
-- 
2.1.0