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authorMark H Weaver <mhw@netris.org>2019-04-01 22:11:35 -0400
committerMark H Weaver <mhw@netris.org>2019-04-16 16:54:55 -0400
commit6b1de860ab2360e8679205aecdc1c837744a4b9c (patch)
tree0357dcee473b12ca590343ad513d876eca1e8199 /libguile/strings.c
parent275c96dd1fbc392e43423e91f08d2cf2fcc538a1 (diff)
downloadguile-6b1de860ab2360e8679205aecdc1c837744a4b9c.tar.gz
Avoid passing NULL to 'memcpy' and 'memcmp'.
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.
Diffstat (limited to 'libguile/strings.c')
-rw-r--r--libguile/strings.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/libguile/strings.c b/libguile/strings.c
index 5f35617a2..62ff2e303 100644
--- a/libguile/strings.c
+++ b/libguile/strings.c
@@ -1,5 +1,5 @@
/* Copyright (C) 1995, 1996, 1998, 2000, 2001, 2004, 2006,
- * 2008-2016, 2018 Free Software Foundation, Inc.
+ * 2008-2016, 2018, 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
@@ -2283,13 +2283,18 @@ scm_to_stringn (SCM str, size_t *lenp, const char *encoding,
size_t
scm_to_locale_stringbuf (SCM str, char *buf, size_t max_len)
{
- size_t len;
+ size_t len, copy_len;
char *result = NULL;
if (!scm_is_string (str))
scm_wrong_type_arg_msg (NULL, 0, str, "string");
result = scm_to_locale_stringn (str, &len);
- memcpy (buf, result, (len > max_len) ? max_len : len);
+ copy_len = (len > max_len) ? max_len : len;
+ if (copy_len != 0)
+ /* Some users of 'scm_to_locale_stringbuf' may pass NULL for buf
+ when max_len is zero, and yet we must avoid passing NULL to
+ memcpy to avoid undefined behavior. */
+ memcpy (buf, result, copy_len);
free (result);
scm_remember_upto_here_1 (str);