libc: add support for reallocarray

This commit adds support for reallocarray function. The functionality
is the same as for standard realloc, but the function also checks for
multiplication overflow and fails safely in case it occurs.

Signed-off-by: Michal Lenc <[email protected]>

include/nuttx/compiler.h

@@ -303,13 +303,15 @@
 #    define malloc_like1(a) __attribute__((__malloc__(__builtin_free, 1))) __attribute__((__alloc_size__(a)))
 #    define malloc_like2(a, b) __attribute__((__malloc__(__builtin_free, 1))) __attribute__((__alloc_size__(a, b)))
 #    define realloc_like(a) __attribute__((__alloc_size__(a)))
+#    define realloc_like2(a, b) __attribute__((__alloc_size__(a, b)))
 #  else
 #    define fopen_like __attribute__((__malloc__))
 #    define popen_like __attribute__((__malloc__))
 #    define malloc_like __attribute__((__malloc__))
 #    define malloc_like1(a) __attribute__((__malloc__)) __attribute__((__alloc_size__(a)))
 #    define malloc_like2(a, b) __attribute__((__malloc__)) __attribute__((__alloc_size__(a, b)))
 #    define realloc_like(a) __attribute__((__alloc_size__(a)))
+#    define realloc_like2(a, b) __attribute__((__alloc_size__(a, b)))
 #  endif
 
 /* Some versions of GCC have a separate __syslog__ format.

include/stdlib.h

@@ -233,6 +233,7 @@ FAR void *malloc(size_t) malloc_like1(1);
 FAR void *valloc(size_t) malloc_like1(1);
 void      free(FAR void *);
 FAR void *realloc(FAR void *, size_t) realloc_like(2);
+FAR void *reallocarray(FAR void *, size_t, size_t) realloc_like2(2, 3);
 FAR void *memalign(size_t, size_t) malloc_like1(2);
 FAR void *zalloc(size_t) malloc_like1(1);
 FAR void *calloc(size_t, size_t) malloc_like2(1, 2);

libs/libc/stdlib/CMakeLists.txt

@@ -39,6 +39,7 @@ set(SRCS
     lib_bsearch.c
     lib_rand.c
     lib_rand48.c
+    lib_reallocarray.c
     lib_qsort.c
     lib_srand.c
     lib_strtol.c

libs/libc/stdlib/Make.defs

@@ -28,6 +28,7 @@ CSRCS += lib_strtoll.c lib_strtoul.c lib_strtoull.c lib_strtold.c
 CSRCS += lib_checkbase.c lib_mktemp.c lib_mkstemp.c lib_mkdtemp.c
 CSRCS += lib_aligned_alloc.c lib_posix_memalign.c lib_valloc.c lib_mblen.c
 CSRCS += lib_mbtowc.c lib_wctomb.c lib_mbstowcs.c lib_wcstombs.c lib_atexit.c
+CSRCS += lib_reallocarray.c
 
 ifeq ($(CONFIG_PSEUDOTERM),y)
 CSRCS += lib_ptsname.c lib_ptsnamer.c lib_unlockpt.c lib_openpty.c

libs/libc/stdlib/lib_reallocarray.c

@@ -0,0 +1,78 @@
+/****************************************************************************
+ * libs/libc/stdlib/lib_reallocarray.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "libc.h"
+
+/****************************************************************************
+ * Pre-processor definitions
+ ****************************************************************************/
+
+/* Set overflow control only if larger than 65536 for bit platforms. The
+ * limit is the same as in OpenBSD.
+ */
+
+#define CHECK_OVERFLOW_LIMIT (1UL << (sizeof(size_t) * 4))
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: reallocarray
+ *
+ * Description:
+ *   The reallocarray function has the same functionality as realloc but
+ *   it fails safely if multiplication overflow occurs.
+ *
+ * Input Parameters:
+ *   ptr   - old memory to be reallocated and freed
+ *   nmemb - number of elements
+ *   size  - size of one element in bytes
+ *
+ * Returned Value:
+ *   Upon successful completion, the address of the re-allocated memory
+ *   is returned and previous pointer is freed. NULL is returned on error
+ *   with original block of memory left unchanged.
+ *
+ ****************************************************************************/
+
+FAR void *reallocarray(FAR void *ptr, size_t nmemb, size_t size)
+{
+  if (nmemb != 0 && (nmemb >= CHECK_OVERFLOW_LIMIT ||
+      size >= CHECK_OVERFLOW_LIMIT))
+    {
+      /* Do division only if at least one element is larget than limit */
+
+      if ((SIZE_MAX / nmemb) < size)
+        {
+          set_errno(ENOMEM);
+          return NULL;
+        }
+    }
+
+  return lib_realloc(ptr, nmemb * size);
+}