#include <wchar.h>
#endif /* ! __STRICT_ANSI__ */
+
+#if __MSVCRT_VERSION__ >= __MSVCR80_DLL
+/* MSVCR80.DLL adds a (mostly) POSIX.1-2008 conforming strnlen(); (it's
+ * also available in MSVCRT.DLL from _WIN32_WINNT_VISTA onwards, but we
+ * pretend otherwise, since recent GCC will try to use the function when
+ * it can be found in libmsvcrt.a, so breaking it for use on WinXP and
+ * earlier).
+ */
+_CRTIMP __cdecl __MINGW_NOTHROW char *strnlen (const char *, size_t);
+
+#elif _POSIX_C_SOURCE >= 200809L
+/* Emulation, to support recent POSIX.1; we prefer this for ALL versions
+ * of MSVCRT.DLL, (even those which already provide strnlen()); to avoid
+ * the GCC breakage noted above. (Note that we implement strnlen() with
+ * the alternative external name, __mingw_strnlen() in libmingwex.a, to
+ * avoid possible link time collision with MSVCR80.DLL's implementation,
+ * then map this to strnlen() via a preprocessor define, so that users
+ * may use it conventionally, (including taking its address); this may
+ * interfere with C++ namespace qualification, but since strnlen() is
+ * not a standard C++ function, we do not anticipate any consequent
+ * usage issues).
+ */
+#define strnlen __mingw_strnlen
+extern size_t __mingw_strnlen (const char *, size_t);
+
+#endif /* _POSIX_C_SOURCE >= 200809L */
+
#undef __STRING_H_SOURCED__
_END_C_DECLS
--- /dev/null
+/*
+ * strnlen.s
+ *
+ * Implementation of POSIX.1-2008 conforming strnlen(), and a wrapper
+ * extending it to conform with ISO-C11 TR-24731-1 strnlen_s().
+ *
+ * $Id$
+ *
+ * Written by Keith Marshall <keithmarshall@users.sourceforge.net>
+ * Copyright (C) 2016, MinGW.org Project
+ *
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ *
+ * This file implements a POSIX.1-2008 conforming strnlen() function, under
+ * the alternative public name of __mingw_strnlen(), (to avoid any possible
+ * conflict with Microsoft's DLL implementations, or a replacement function
+ * implemented by the user).
+ *
+ * Note that POSIX does not prescribe any error returns for its strnlen()
+ * function; in particular, it does not specify handling of a NULL pointer,
+ * passed as the string argument to count, and thus, a segmentation fault
+ * is a plausible outcome. This is consistent with the behaviour exhibited
+ * by Microsoft's implementation, and this implementation acts likewise.
+ *
+ * OTOH, ISO-C11 TR-24731-1 prescribes that strnlen_s() shall return zero,
+ * when passed a NULL pointer as the string argument; the alternative entry
+ * point, __mingw_strnlen_s(), checks for this anomaly, and acts accordingly,
+ * before continuing as for __mingw_strnlen(), when passed a valid pointer
+ * to a string argument; (this is consistent with the documented behaviour
+ * of Microsoft's strnlen_s() implementation).
+ *
+ * Note that I've chosen to implement this in assembly language to enable
+ * sharing of common code between two distinct entry points, with subtly
+ * differing behaviours, while avoiding the overhead of an extra function
+ * call to invoke such shared code; this also allows the code to exploit
+ * the CUP's string scanning instructions, (which GCC does not), and so
+ * achieves a more compact, (and likely more efficient), implementation.
+ *
+ */
+.text
+.align 4
+.globl ___mingw_strnlen
+.def ___mingw_strnlen; .scl 2; .type 32; .endef
+
+___mingw_strnlen:
+/* Implements: size_t __mingw_strnlen (const char *string, size_t maxlen );
+ *
+ * Scans at most maxlen chars, returning the lesser of strlen (string) and
+ * maxlen; does NOT check for string == NULL, which may thus induce failure
+ * with a segmentation fault. Note that initialization of return count to
+ * zero, in EAX, also serves as the NUL char reference for SCASB, in AL.
+ */
+ pushl %edi /* must preserve this */
+ xorl %eax, %eax /* initialize return count to zero */
+ movl 8(%esp), %edx /* load address of string argument */
+.L1:
+ movl 12(%esp), %ecx /* load maxlen ... */
+ jecxz .L4 /* and jump to end, if it's zero */
+.L2:
+ cld /* scan string from low-->high address */
+ movl %edx, %edi /* using this as the scan pointer ... */
+ repne scasb /* as required by this CPU scan */
+ mov %edi, %eax /* note where we stopped ... */
+ jz .L3 /* but if we found NUL, we've overrun ... */
+ decl %eax /* so we need to adjust one byte backward */
+.L3:
+ sub %edx, %eax /* compute effective count to return */
+.L4:
+ popl %edi /* restore saved register ... */
+ ret /* and we're done */
+
+.align 4
+.globl ___mingw_strnlen_s
+.def ___mingw_strnlen_s; .scl 2; .type 32; .endef
+
+___mingw_strnlen_s:
+/* Implements: size_t __mingw_strnlen_s (const char *string, size_t maxlen );
+ *
+ * Exhibits identical behaviour to __mingw_strnlen(), EXCEPT that it DOES
+ * check for string == NULL, returning zero when found.
+ */
+ pushl %edi /* must preserve this */
+ xorl %eax, %eax /* initialize return count to zero */
+ movl 8(%esp), %edx /* load address of string argument ... */
+ testl %edx, %edx /* checking for NULL pointer, and ... */
+ jnz .L1 /* proceeding as strnlen(), if not ... */
+ popl %edi /* otherwise restore saved register ... */
+ ret /* and return zero count value */
+
+/* $RCSfile$: end of file */
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