Implement allocation buffers for internal use

This commit adds fixed-size allocation buffers.  The primary use
case is in NSS modules, where dynamically sized data is stored
in a fixed-size buffer provided by the caller.

Other uses include a replacement of mempcpy cascades (which is
safer due to the size checking inherent to allocation buffers).

8 files changed, 856 insertions, 1 deletions

diff --git a/malloc/Makefile b/malloc/Makefile
index 14c13f1..b50de7c 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -33,6 +33,7 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
 	 tst-mallocfork2 \
 	 tst-interpose-nothread \
 	 tst-interpose-thread \
+	 tst-alloc_buffer \
 
 tests-static := \
 	 tst-interpose-static-nothread \
@@ -63,6 +64,11 @@ routines = malloc morecore mcheck mtrace obstack reallocarray \
   dynarray_finalize \
   dynarray_resize \
   dynarray_resize_clear \
+  alloc_buffer_alloc_array \
+  alloc_buffer_allocate \
+  alloc_buffer_copy_bytes  \
+  alloc_buffer_copy_string \
+  alloc_buffer_create_failure \
 
 install-lib := libmcheck.a
 non-lib.a := libmcheck.a
diff --git a/malloc/Versions b/malloc/Versions
index 5b54306..2357cff 100644
--- a/malloc/Versions
+++ b/malloc/Versions
@@ -76,7 +76,6 @@ libc {
     __libc_scratch_buffer_grow_preserve;
     __libc_scratch_buffer_set_array_size;
 
-
     # Internal name for reallocarray
     __libc_reallocarray;
 
@@ -86,5 +85,12 @@ libc {
     __libc_dynarray_finalize;
     __libc_dynarray_resize;
     __libc_dynarray_resize_clear;
+
+    # struct alloc_buffer support
+    __libc_alloc_buffer_alloc_array;
+    __libc_alloc_buffer_allocate;
+    __libc_alloc_buffer_copy_bytes;
+    __libc_alloc_buffer_copy_string;
+    __libc_alloc_buffer_create_failure;
   }
 }
diff --git a/malloc/alloc_buffer_alloc_array.c b/malloc/alloc_buffer_alloc_array.c
new file mode 100644
index 0000000..68e14da
--- /dev/null
+++ b/malloc/alloc_buffer_alloc_array.c
@@ -0,0 +1,47 @@
+/* Array allocation from a fixed-size buffer.
+   Copyright (C) 2017 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 <alloc_buffer.h>
+#include <malloc-internal.h>
+#include <libc-pointer-arith.h>
+
+void *
+__libc_alloc_buffer_alloc_array (struct alloc_buffer *buf, size_t element_size,
+                                 size_t align, size_t count)
+{
+  size_t current = buf->__alloc_buffer_current;
+  /* The caller asserts that align is a power of two.  */
+  size_t aligned = ALIGN_UP (current, align);
+  size_t size;
+  bool overflow = check_mul_overflow_size_t (element_size, count, &size);
+  size_t new_current = aligned + size;
+  if (!overflow                /* Multiplication did not overflow.  */
+      && aligned >= current    /* No overflow in align step.  */
+      && new_current >= size   /* No overflow in size computation.  */
+      && new_current <= buf->__alloc_buffer_end) /* Room in buffer.  */
+    {
+      buf->__alloc_buffer_current = new_current;
+      return (void *) aligned;
+    }
+  else
+    {
+      alloc_buffer_mark_failed (buf);
+      return NULL;
+    }
+}
+libc_hidden_def (__libc_alloc_buffer_alloc_array)
diff --git a/malloc/alloc_buffer_allocate.c b/malloc/alloc_buffer_allocate.c
new file mode 100644
index 0000000..cbde72b
--- /dev/null
+++ b/malloc/alloc_buffer_allocate.c
@@ -0,0 +1,36 @@
+/* Allocate a fixed-size allocation buffer using malloc.
+   Copyright (C) 2017 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 <alloc_buffer.h>
+
+#include <stdlib.h>
+
+struct alloc_buffer
+__libc_alloc_buffer_allocate (size_t size, void **pptr)
+{
+  *pptr = malloc (size);
+  if (*pptr == NULL)
+    return (struct alloc_buffer)
+      {
+        .__alloc_buffer_current = __ALLOC_BUFFER_INVALID_POINTER,
+        .__alloc_buffer_end = __ALLOC_BUFFER_INVALID_POINTER
+      };
+  else
+    return alloc_buffer_create (*pptr, size);
+}
+libc_hidden_def (__libc_alloc_buffer_allocate)
diff --git a/malloc/alloc_buffer_copy_bytes.c b/malloc/alloc_buffer_copy_bytes.c
new file mode 100644
index 0000000..66196f1
--- /dev/null
+++ b/malloc/alloc_buffer_copy_bytes.c
@@ -0,0 +1,34 @@
+/* Copy an array of bytes into the buffer.
+   Copyright (C) 2017 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 <alloc_buffer.h>
+
+#include <string.h>
+
+/* This function works on a copy of the buffer object, so that it can
+   remain non-addressable in the caller.  */
+struct alloc_buffer
+__libc_alloc_buffer_copy_bytes (struct alloc_buffer buf,
+                                const void *src, size_t len)
+{
+  void *ptr = alloc_buffer_alloc_bytes (&buf, len);
+  if (ptr != NULL)
+    memcpy (ptr, src, len);
+  return buf;
+}
+libc_hidden_def (__libc_alloc_buffer_copy_bytes)
diff --git a/malloc/alloc_buffer_copy_string.c b/malloc/alloc_buffer_copy_string.c
new file mode 100644
index 0000000..77c0023
--- /dev/null
+++ b/malloc/alloc_buffer_copy_string.c
@@ -0,0 +1,30 @@
+/* Copy a string into the allocation buffer.
+   Copyright (C) 2017 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 <alloc_buffer.h>
+
+#include <string.h>
+
+/* This function works on a copy of the buffer object, so that it can
+   remain non-addressable in the caller.  */
+struct alloc_buffer
+__libc_alloc_buffer_copy_string (struct alloc_buffer buf, const char *src)
+{
+  return __libc_alloc_buffer_copy_bytes (buf, src, strlen (src) + 1);
+}
+libc_hidden_def (__libc_alloc_buffer_copy_string)
diff --git a/malloc/alloc_buffer_create_failure.c b/malloc/alloc_buffer_create_failure.c
new file mode 100644
index 0000000..5ffba22
--- /dev/null
+++ b/malloc/alloc_buffer_create_failure.c
@@ -0,0 +1,31 @@
+/* Terminate the process as the result of an invalid allocation buffer.
+   Copyright (C) 2017 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 <alloc_buffer.h>
+#include <stdio.h>
+
+void
+__libc_alloc_buffer_create_failure (void *start, size_t size)
+{
+  char buf[200];
+  __snprintf (buf, sizeof (buf), "Fatal glibc error: "
+              "invalid allocation buffer of size %zu\n",
+              size);
+  __libc_fatal (buf);
+}
+libc_hidden_def (__libc_alloc_buffer_create_failure)
diff --git a/malloc/tst-alloc_buffer.c b/malloc/tst-alloc_buffer.c
new file mode 100644
index 0000000..1c14399
--- /dev/null
+++ b/malloc/tst-alloc_buffer.c
@@ -0,0 +1,665 @@
+/* Tests for struct alloc_buffer.
+   Copyright (C) 2017 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 <arpa/inet.h>
+#include <alloc_buffer.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+
+/* Return true if PTR is sufficiently aligned for TYPE.  */
+#define IS_ALIGNED(ptr, type) \
+  ((((uintptr_t) ptr) & (__alloc_buffer_assert_align (__alignof (type)) - 1)) \
+   == 0)
+
+/* Structure with non-power-of-two size.  */
+struct twelve
+{
+  uint32_t buffer[3] __attribute__ ((aligned (4)));
+};
+_Static_assert (sizeof (struct twelve) == 12, "struct twelve");
+_Static_assert (__alignof__ (struct twelve) == 4, "struct twelve");
+
+/* Check for success obtaining empty arrays.  Does not assume the
+   buffer is empty.  */
+static void
+test_empty_array (struct alloc_buffer refbuf)
+{
+  bool refbuf_failed = alloc_buffer_has_failed (&refbuf);
+  if (test_verbose)
+    printf ("info: %s: current=0x%llx end=0x%llx refbuf_failed=%d\n",
+            __func__, (unsigned long long) refbuf.__alloc_buffer_current,
+            (unsigned long long) refbuf.__alloc_buffer_end, refbuf_failed);
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY ((alloc_buffer_alloc_bytes (&buf, 0) == NULL)
+                 == refbuf_failed);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf) == refbuf_failed);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY ((alloc_buffer_alloc_array (&buf, char, 0) == NULL)
+                 == refbuf_failed);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf) == refbuf_failed);
+  }
+  /* The following tests can fail due to the need for aligning the
+     returned pointer.  */
+  {
+    struct alloc_buffer buf = refbuf;
+    bool expect_failure = refbuf_failed
+      || !IS_ALIGNED (alloc_buffer_next (&buf, void), double);
+    double *ptr = alloc_buffer_alloc_array (&buf, double, 0);
+    TEST_VERIFY (IS_ALIGNED (ptr, double));
+    TEST_VERIFY ((ptr == NULL) == expect_failure);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf) == expect_failure);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    bool expect_failure = refbuf_failed
+      || !IS_ALIGNED (alloc_buffer_next (&buf, void), struct twelve);
+    struct twelve *ptr = alloc_buffer_alloc_array (&buf, struct twelve, 0);
+    TEST_VERIFY (IS_ALIGNED (ptr, struct twelve));
+    TEST_VERIFY ((ptr == NULL) == expect_failure);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf) == expect_failure);
+  }
+}
+
+/* Test allocation of impossibly large arrays.  */
+static void
+test_impossible_array (struct alloc_buffer refbuf)
+{
+  if (test_verbose)
+    printf ("info: %s: current=0x%llx end=0x%llx\n",
+            __func__, (unsigned long long) refbuf.__alloc_buffer_current,
+            (unsigned long long) refbuf.__alloc_buffer_end);
+  static const size_t counts[] =
+    { SIZE_MAX, SIZE_MAX - 1, SIZE_MAX - 2, SIZE_MAX - 3, SIZE_MAX - 4,
+      SIZE_MAX / 2, SIZE_MAX / 2 + 1, SIZE_MAX / 2 - 1, 0};
+
+  for (int i = 0; counts[i] != 0; ++i)
+    {
+      size_t count = counts[i];
+      if (test_verbose)
+        printf ("info: %s: count=%zu\n", __func__, count);
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_bytes (&buf, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, char, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, short, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, double, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, struct twelve, count)
+                     == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+    }
+}
+
+/* Check for failure to obtain anything from a failed buffer.  */
+static void
+test_after_failure (struct alloc_buffer refbuf)
+{
+  if (test_verbose)
+    printf ("info: %s: current=0x%llx end=0x%llx\n",
+            __func__, (unsigned long long) refbuf.__alloc_buffer_current,
+            (unsigned long long) refbuf.__alloc_buffer_end);
+  TEST_VERIFY (alloc_buffer_has_failed (&refbuf));
+  {
+    struct alloc_buffer buf = refbuf;
+    alloc_buffer_add_byte (&buf, 17);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, char) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, double) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, struct twelve) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+  }
+
+  test_impossible_array (refbuf);
+  for (int count = 0; count <= 4; ++count)
+    {
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_bytes (&buf, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, char, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, double, count) == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+      {
+        struct alloc_buffer buf = refbuf;
+        TEST_VERIFY (alloc_buffer_alloc_array (&buf, struct twelve, count)
+                     == NULL);
+        TEST_VERIFY (alloc_buffer_has_failed (&buf));
+      }
+    }
+}
+
+static void
+test_empty (struct alloc_buffer refbuf)
+{
+  TEST_VERIFY (alloc_buffer_size (&refbuf) == 0);
+  if (alloc_buffer_next (&refbuf, void) != NULL)
+    TEST_VERIFY (!alloc_buffer_has_failed (&refbuf));
+  test_empty_array (refbuf);
+  test_impossible_array (refbuf);
+
+  /* Failure to obtain non-empty objects.  */
+  {
+    struct alloc_buffer buf = refbuf;
+    alloc_buffer_add_byte (&buf, 17);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, char) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, double) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, struct twelve) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, char, 1) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, double, 1) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, struct twelve, 1) == NULL);
+    test_after_failure (buf);
+  }
+}
+
+static void
+test_size_1 (struct alloc_buffer refbuf)
+{
+  TEST_VERIFY (!alloc_buffer_has_failed (&refbuf));
+  TEST_VERIFY (alloc_buffer_size (&refbuf) == 1);
+  test_empty_array (refbuf);
+  test_impossible_array (refbuf);
+
+  /* Success adding a single byte.  */
+  {
+    struct alloc_buffer buf = refbuf;
+    alloc_buffer_add_byte (&buf, 17);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    test_empty (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "\x11", 1) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    signed char *ptr = alloc_buffer_alloc (&buf, signed char);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    *ptr = 126;
+    test_empty (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "\176", 1) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    char *ptr = alloc_buffer_alloc_array (&buf, char, 1);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    *ptr = (char) 253;
+    test_empty (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "\xfd", 1) == 0);
+
+  /* Failure with larger objects.  */
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, short) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, double) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, struct twelve) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, short, 1) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, double, 1) == NULL);
+    test_after_failure (buf);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, struct twelve, 1) == NULL);
+    test_after_failure (buf);
+  }
+}
+
+static void
+test_size_2 (struct alloc_buffer refbuf)
+{
+  TEST_VERIFY (!alloc_buffer_has_failed (&refbuf));
+  TEST_VERIFY (alloc_buffer_size (&refbuf) == 2);
+  TEST_VERIFY (IS_ALIGNED (alloc_buffer_next (&refbuf, void), short));
+  test_empty_array (refbuf);
+  test_impossible_array (refbuf);
+
+  /* Success adding two bytes.  */
+  {
+    struct alloc_buffer buf = refbuf;
+    alloc_buffer_add_byte (&buf, '@');
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    test_size_1 (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "@\xfd", 2) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    signed char *ptr = alloc_buffer_alloc (&buf, signed char);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    *ptr = 'A';
+    test_size_1 (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "A\xfd", 2) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    char *ptr = alloc_buffer_alloc_array (&buf, char, 1);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    *ptr = 'B';
+    test_size_1 (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "B\xfd", 2) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    unsigned short *ptr = alloc_buffer_alloc (&buf, unsigned short);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (IS_ALIGNED (ptr, unsigned short));
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    *ptr = htons (0x12f4);
+    test_empty (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "\x12\xf4", 2) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    unsigned short *ptr = alloc_buffer_alloc_array (&buf, unsigned short, 1);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (IS_ALIGNED (ptr, unsigned short));
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    *ptr = htons (0x13f5);
+    test_empty (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "\x13\xf5", 2) == 0);
+  {
+    struct alloc_buffer buf = refbuf;
+    char *ptr = alloc_buffer_alloc_array (&buf, char, 2);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    memcpy (ptr, "12", 2);
+    test_empty (buf);
+  }
+  TEST_VERIFY (memcmp (alloc_buffer_next (&refbuf, void), "12", 2) == 0);
+}
+
+static void
+test_misaligned (char pad)
+{
+  enum { SIZE = 23 };
+  char *backing = xmalloc (SIZE + 2);
+  backing[0] = ~pad;
+  backing[SIZE + 1] = pad;
+  struct alloc_buffer refbuf = alloc_buffer_create (backing + 1, SIZE);
+
+  {
+    struct alloc_buffer buf = refbuf;
+    short *ptr = alloc_buffer_alloc_array (&buf, short, SIZE / sizeof (short));
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (IS_ALIGNED (ptr, short));
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    for (int i = 0; i < SIZE / sizeof (short); ++i)
+      ptr[i] = htons (0xff01 + i);
+    TEST_VERIFY (memcmp (ptr,
+                         "\xff\x01\xff\x02\xff\x03\xff\x04"
+                         "\xff\x05\xff\x06\xff\x07\xff\x08"
+                         "\xff\x09\xff\x0a\xff\x0b", 22) == 0);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    uint32_t *ptr = alloc_buffer_alloc_array
+      (&buf, uint32_t, SIZE / sizeof (uint32_t));
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (IS_ALIGNED (ptr, uint32_t));
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    for (int i = 0; i < SIZE / sizeof (uint32_t); ++i)
+      ptr[i] = htonl (0xf1e2d301 + i);
+    TEST_VERIFY (memcmp (ptr,
+                         "\xf1\xe2\xd3\x01\xf1\xe2\xd3\x02"
+                         "\xf1\xe2\xd3\x03\xf1\xe2\xd3\x04"
+                         "\xf1\xe2\xd3\x05", 20) == 0);
+  }
+  {
+    struct alloc_buffer buf = refbuf;
+    struct twelve *ptr = alloc_buffer_alloc (&buf, struct twelve);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (IS_ALIGNED (ptr, struct twelve));
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    ptr->buffer[0] = htonl (0x11223344);
+    ptr->buffer[1] = htonl (0x55667788);
+    ptr->buffer[2] = htonl (0x99aabbcc);
+    TEST_VERIFY (memcmp (ptr,
+                         "\x11\x22\x33\x44"
+                         "\x55\x66\x77\x88"
+                         "\x99\xaa\xbb\xcc", 12) == 0);
+  }
+  {
+    static const double nums[] = { 1, 2 };
+    struct alloc_buffer buf = refbuf;
+    double *ptr = alloc_buffer_alloc_array (&buf, double, 2);
+    TEST_VERIFY_EXIT (ptr != NULL);
+    TEST_VERIFY (IS_ALIGNED (ptr, double));
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    ptr[0] = nums[0];
+    ptr[1] = nums[1];
+    TEST_VERIFY (memcmp (ptr, nums, sizeof (nums)) == 0);
+  }
+
+  /* Verify that padding was not overwritten.  */
+  TEST_VERIFY (backing[0] == ~pad);
+  TEST_VERIFY (backing[SIZE + 1] == pad);
+  free (backing);
+}
+
+/* Check that overflow during alignment is handled properly.  */
+static void
+test_large_misaligned (void)
+{
+  uintptr_t minus1 = -1;
+  uintptr_t start = minus1 & ~0xfe;
+  struct alloc_buffer refbuf = alloc_buffer_create ((void *) start, 16);
+  TEST_VERIFY (!alloc_buffer_has_failed (&refbuf));
+
+  struct __attribute__ ((aligned (256))) align256
+  {
+    int dymmy;
+  };
+
+  {
+    struct alloc_buffer buf = refbuf;
+    TEST_VERIFY (alloc_buffer_alloc (&buf, struct align256) == NULL);
+    test_after_failure (buf);
+  }
+  for (int count = 0; count < 3; ++count)
+    {
+      struct alloc_buffer buf = refbuf;
+      TEST_VERIFY (alloc_buffer_alloc_array (&buf, struct align256, count)
+                   == NULL);
+      test_after_failure (buf);
+    }
+}
+
+/* Check behavior of large allocations.  */
+static void
+test_large (void)
+{
+  {
+    /* Allocation which wraps around.  */
+    struct alloc_buffer buf = { 1, SIZE_MAX };
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, char, SIZE_MAX) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+  }
+
+  {
+    /* Successful very large allocation.  */
+    struct alloc_buffer buf = { 1, SIZE_MAX };
+    uintptr_t val = (uintptr_t) alloc_buffer_alloc_array
+      (&buf, char, SIZE_MAX - 1);
+    TEST_VERIFY (val == 1);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    test_empty (buf);
+  }
+
+  {
+    typedef char __attribute__ ((aligned (2))) char2;
+
+    /* Overflow in array size computation.   */
+    struct alloc_buffer buf = { 1, SIZE_MAX };
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, char2, SIZE_MAX - 1) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+
+    /* Successful allocation after alignment.  */
+    buf = (struct alloc_buffer) { 1, SIZE_MAX };
+    uintptr_t val = (uintptr_t) alloc_buffer_alloc_array
+      (&buf, char2, SIZE_MAX - 2);
+    TEST_VERIFY (val == 2);
+    test_empty (buf);
+
+    /* Alignment behavior near the top of the address space.  */
+    buf = (struct alloc_buffer) { SIZE_MAX, SIZE_MAX };
+    TEST_VERIFY (alloc_buffer_next (&buf, char2) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+    buf = (struct alloc_buffer) { SIZE_MAX, SIZE_MAX };
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, char2, 0) == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+  }
+
+  {
+    typedef short __attribute__ ((aligned (2))) short2;
+
+    /* Test overflow in size computation.  */
+    struct alloc_buffer buf = { 1, SIZE_MAX };
+    TEST_VERIFY (alloc_buffer_alloc_array (&buf, short2, SIZE_MAX / 2)
+                 == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+
+    /* A slightly smaller array fits within the allocation.  */
+    buf = (struct alloc_buffer) { 2, SIZE_MAX - 1 };
+    uintptr_t val = (uintptr_t) alloc_buffer_alloc_array
+      (&buf, short2, SIZE_MAX / 2 - 1);
+    TEST_VERIFY (val == 2);
+    test_empty (buf);
+  }
+}
+
+static void
+test_copy_bytes (void)
+{
+  char backing[4];
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    alloc_buffer_copy_bytes (&buf, "1", 1);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 3);
+    TEST_VERIFY (memcmp (backing, "1@@@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    alloc_buffer_copy_bytes (&buf, "12", 3);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 1);
+    TEST_VERIFY (memcmp (backing, "12\0@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    alloc_buffer_copy_bytes (&buf, "1234", 4);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 0);
+    TEST_VERIFY (memcmp (backing, "1234", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    alloc_buffer_copy_bytes (&buf, "1234", 5);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (memcmp (backing, "@@@@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    alloc_buffer_copy_bytes (&buf, "1234", -1);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (memcmp (backing, "@@@@", 4) == 0);
+  }
+}
+
+static void
+test_copy_string (void)
+{
+  char backing[4];
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    const char *p = alloc_buffer_copy_string (&buf, "");
+    TEST_VERIFY (p == backing);
+    TEST_VERIFY (strcmp (p, "") == 0);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 3);
+    TEST_VERIFY (memcmp (backing, "\0@@@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    const char *p = alloc_buffer_copy_string (&buf, "1");
+    TEST_VERIFY (p == backing);
+    TEST_VERIFY (strcmp (p, "1") == 0);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 2);
+    TEST_VERIFY (memcmp (backing, "1\0@@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    const char *p = alloc_buffer_copy_string (&buf, "12");
+    TEST_VERIFY (p == backing);
+    TEST_VERIFY (strcmp (p, "12") == 0);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 1);
+    TEST_VERIFY (memcmp (backing, "12\0@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    const char *p = alloc_buffer_copy_string (&buf, "123");
+    TEST_VERIFY (p == backing);
+    TEST_VERIFY (strcmp (p, "123") == 0);
+    TEST_VERIFY (!alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (alloc_buffer_size (&buf) == 0);
+    TEST_VERIFY (memcmp (backing, "123", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    TEST_VERIFY (alloc_buffer_copy_string (&buf, "1234") == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (memcmp (backing, "@@@@", 4) == 0);
+  }
+  {
+    memset (backing, '@', sizeof (backing));
+    struct alloc_buffer buf = alloc_buffer_create (backing, sizeof (backing));
+    TEST_VERIFY (alloc_buffer_copy_string (&buf, "12345") == NULL);
+    TEST_VERIFY (alloc_buffer_has_failed (&buf));
+    TEST_VERIFY (memcmp (backing, "@@@@", 4) == 0);
+  }
+}
+
+static int
+do_test (void)
+{
+  test_empty (alloc_buffer_create (NULL, 0));
+  test_empty (alloc_buffer_create ((char *) "", 0));
+  test_empty (alloc_buffer_create ((void *) 1, 0));
+
+  {
+    void *ptr = (void *) "";    /* Cannot be freed. */
+    struct alloc_buffer buf = alloc_buffer_allocate (1, &ptr);
+    test_size_1 (buf);
+    free (ptr);                 /* Should have been overwritten.  */
+  }
+
+  {
+    void *ptr= (void *) "";     /* Cannot be freed.  */
+    struct alloc_buffer buf = alloc_buffer_allocate (2, &ptr);
+    test_size_2 (buf);
+    free (ptr);                 /* Should have been overwritten.  */
+  }
+
+  test_misaligned (0);
+  test_misaligned (0xc7);
+  test_misaligned (0xff);
+
+  test_large_misaligned ();
+  test_large ();
+  test_copy_bytes ();
+  test_copy_string ();
+
+  return 0;
+}
+
+#include <support/test-driver.c>