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/* Test of strncpy() function.
Copyright (C) 2010-2026 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include <string.h>
#include <stddef.h>
#include "zerosize-ptr.h"
#include "macros.h"
/* Test the library, not the compiler+library. */
static char *
lib_strncpy (char *s1, char const *s2, size_t n)
{
return strncpy (s1, s2, n);
}
static char *(*volatile volatile_strncpy) (char *, char const *, size_t)
= lib_strncpy;
#undef strncpy
#define strncpy volatile_strncpy
#define MAGIC (char)0xBA
static void
check_single (const char *input, size_t length, size_t n)
{
char *dest;
char *result;
dest = (char *) malloc (1 + n + 1);
ASSERT (dest != NULL);
for (size_t i = 0; i < 1 + n + 1; i++)
dest[i] = MAGIC;
result = strncpy (dest + 1, input, n);
ASSERT (result == dest + 1);
ASSERT (dest[0] == MAGIC);
{
size_t i;
for (i = 0; i < (n <= length ? n : length + 1); i++)
ASSERT (dest[1 + i] == input[i]);
for (; i < n; i++)
ASSERT (dest[1 + i] == 0);
}
ASSERT (dest[1 + n] == MAGIC);
free (dest);
}
static void
check (const char *input, size_t input_length)
{
size_t length;
ASSERT (input_length > 0);
ASSERT (input[input_length - 1] == 0);
length = input_length - 1; /* = strlen (input) */
for (size_t n = 0; n <= 2 * length + 2; n++)
check_single (input, length, n);
/* Check that strncpy (D, S, N) does not look at more than
MIN (strlen (S) + 1, N) units. */
{
char *page_boundary = (char *) zerosize_ptr ();
if (page_boundary != NULL)
{
for (size_t n = 0; n <= 2 * length + 2; n++)
{
size_t n_to_copy = (n <= length ? n : length + 1);
char *copy;
copy = (char *) page_boundary - n_to_copy;
for (size_t i = 0; i < n_to_copy; i++)
copy[i] = input[i];
check_single (copy, length, n);
}
}
}
}
int
main (void)
{
/* Simple string. */
{ /* "Grüß Gott." */
static const char input[] = "Gr\303\274\303\237 Gott.";
check (input, SIZEOF (input));
}
/* Test zero-length operations on NULL pointers, allowed by
<https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3322.pdf>. */
ASSERT (strncpy (NULL, "x", 0) == NULL);
{
char y[1];
ASSERT (strncpy (y, NULL, 0) == y);
}
return test_exit_status;
}
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