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Avoid passing NULL to 'memcpy' and 'memcmp'.

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Reported by Jeffrey Walton <noloader@gmail.com> in
<https://lists.gnu.org/archive/html/guile-devel/2019-03/msg00001.html>.

Note that C11 section 7.1.4 (Use of library functions) states that:
"unless explicitly stated otherwise in the detailed descriptions [of
library functions] that follow: If an argument to a function has an
invalid value (such as ... a null pointer ...) ..., the behavior is
undefined."  Note that 'strxfrm' is an example of a standard C function
that explicitly states otherwise, allowing NULL to be passed in the
first argument if the size argument is zero, but no similar allowance is
specified for 'memcpy' or 'memcmp'.

* libguile/bytevectors.c (scm_uniform_array_to_bytevector): Call memcpy
only if 'byte_len' is non-zero.
* libguile/srfi-14.c (charsets_equal): Call memcmp only if the number of
ranges is non-zero.
* libguile/stime.c (setzone): Pass 1-character buffer to
'scm_to_locale_stringbuf', instead of NULL.
* libguile/strings.c (scm_to_locale_stringbuf): Call memcpy only if the
number of bytes to copy is non-zero.
This commit is contained in:
Mark H Weaver 2019-04-01 22:11:35 -04:00
parent 275c96dd1f
commit 6b1de860ab
4 changed files with 24 additions and 7 deletions
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8
libguile/bytevectors.c
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@ -1,4 +1,4 @@
/* Copyright (C) 2009-2015 Free Software Foundation, Inc.
/* Copyright (C) 2009-2015, 2019 Free Software Foundation, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
@ -662,7 +662,11 @@ SCM_DEFINE (scm_uniform_array_to_bytevector, "uniform-array->bytevector",
SCM_MISC_ERROR ("uniform elements larger than 8 bits must fill whole bytes", SCM_EOL);
ret = make_bytevector (byte_len, SCM_ARRAY_ELEMENT_TYPE_VU8);
memcpy (SCM_BYTEVECTOR_CONTENTS (ret), elts, byte_len);
if (byte_len != 0)
/* Empty arrays may have elements == NULL. We must avoid passing
NULL to memcpy, even if the length is zero, to avoid undefined
behavior. */
memcpy (SCM_BYTEVECTOR_CONTENTS (ret), elts, byte_len);
scm_array_handle_release (&h);