2008/11/9 Dominique Pelle <[EMAIL PROTECTED]>:
> $ gcc -Wall -o test-memcpy-memmove test-memcpy-memmove.c
> $ ./memcpy-memmove
> testing descending memcpy() with overlapping mem...OK
> testing ascending memcpy() with overlapping mem...FAIL
> expected=[abcdeabcdeabcdepqrstuvwxyz]
> actual =[abcdeabcdefghijpqrstuvwxyz]
> testing descending memmove() with overlapping mem...OK
> testing ascending memmove() with overlapping mem...OK
Oops, small mistake, which does not change the conclusion,
output should have been:
$ ./memcpy-memmove
testing descending memcpy() with overlapping mem...OK
testing ascending memcpy() with overlapping mem...FAIL
expected=[abcdeabcdefghijpqrstuvwxyz]
actual =[abcdeabcdeabcdepqrstuvwxyz]
testing descending memmove() with overlapping mem...OK
testing ascending memmove() with overlapping mem...OK
-- Dominique
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/*
* Test whether memcpy()/memmove() give the correct
* results when moving overlapping memory upward or
* backward. mempcy() is not guarantee to be correct
* when memory overlaps, memmove() should be correct.
*
* Results on my system (Linux x86):
*
* $ gcc -O2 -Wall -o test-memcpy-memmove test-memcpy-memmove.c
* $ ./test-memcpy-memmove
* testing descending memcpy() with overlapping mem...OK
* testing ascending memcpy() with overlapping mem...FAIL
* expected=[abcdeabcdefghijpqrstuvwxyz]
* actual =[abcdeabcdeabcdepqrstuvwxyz]
* testing descending memmove() with overlapping mem...OK
* testing ascending memmove() with overlapping mem...OK
*
* Dominique Pelle <[EMAIL PROTECTED]>
*/
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
/* Compare expected and actual results, and print outcome */
static void compare(const char *expected, const char *actual)
{
if (strcmp(expected, actual) == 0) {
printf("OK\n");
} else {
printf("FAIL\n"
" expected=[%s]\n"
" actual =[%s]\n", expected, actual);
}
}
int main()
{
/* 0 1 2
* .........................01234567890123456789012345 */
const char *pristine_str = "abcdefghijklmnopqrstuvwxyz";
char *str;
/* Expected results when copying 10 char by 5 positions (hence
* overlapping memory).
*
* When copying downward memmove(str, str + 5, 10)
* (.) for unchanged char (X) for changed char:
*
* pristine: abcdefghijklmnopqrstuvwxyx
* XXXXXXXXXX................ */
const const char *expected1 = "fghijklmnoklmnopqrstuvwxyz";
/*
* When copying upward memmove(str + 5, str, 10)
* (.) for unchanged char (X) for changed char:
*
* pristine: abcdefghijklmnopqrstuvwxyx
* .....XXXXXXXXXX........... */
const const char *expected2 = "abcdeabcdefghijpqrstuvwxyz";
printf("testing descending memcpy() with overlapping mem...");
str = strdup(pristine_str);
memcpy(str, str + 5, 10);
compare(expected1, str);
printf("testing ascending memcpy() with overlapping mem...");
strcpy(str, pristine_str);
memcpy(str + 5, str, 10);
compare(expected2, str);
printf("testing descending memmove() with overlapping mem...");
strcpy(str, pristine_str);
memmove(str, str + 5, 10);
compare(expected1, str);
printf("testing ascending memmove() with overlapping mem...");
strcpy(str, pristine_str);
memmove(str + 5, str, 10);
compare(expected2, str);
free(str);
return 0;
}
