memset, memset_s
From cppreference.com
Defined in header
<string.h>
|
||
void *memset( void *dest, int ch, size_t count );
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(1) | |
errno_t memset_s( void *dest, rsize_t destsz, int ch, rsize_t count )
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(2) | (since C11) |
1) Converts the value
ch
to unsigned char and copies it into each of the first count
characters of the object pointed to by dest
.
2) Same as (1), except that the following errors are detected at runtime and call the currently installed constraint handler function after storing
ch
in every location of the destination range [dest, dest+destsz) if dest
and destsz
are themselves valid:
-
-
dest
is a null pointer -
destsz
orcount
is greater than RSIZE_MAX -
count
is greater thandestsz
-
- As all bounds-checked functions,
memset_s
is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before includingstring.h
.
Contents |
[edit] Parameters
dest | - | pointer to the object to fill |
ch | - | fill byte |
count | - | number of bytes to fill |
destsz | - | size of the destination array |
[edit] Return value
1) A copy of
dest
2) zero on success, non-zero on error. Also on error, if
dest
is not a null pointer and destsz
is valid, writes destsz
fill bytes ch
to the destination array.[edit] Notes
memset
may be optimized away (under the as-if rules) if the object modified by this function is not accessed again for the rest of its lifetime. For that reason, this function cannot be used to scrub memory (e.g. to fill an array that stored a password with zeroes). This optimization is prohibited for memset_s
: it is guaranteed to perform the memory write.
[edit] Example
Run this code
Output:
ghghghghghghghghghghgh aaaaahghghghghghghghgh
[edit] References
- C11 standard (ISO/IEC 9899:2011):
-
- 7.24.6.1 The memset function (p: 371)
-
- K.3.7.4.1 The memset_s function (p: 621-622)
- C99 standard (ISO/IEC 9899:1999):
-
- 7.21.6.1 The memset function (p: 333)
- C89/C90 standard (ISO/IEC 9899:1990):
-
- 4.11.6.1 The memset function
[edit] See also
(C11)
|
copies one buffer to another (function) |
(C95)
|
copies the given wide character to every position in a wide character array (function) |
C++ documentation for memset
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