std::memset
Defined in header <cstring>
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void
* memset(
void
* dest, int ch, std::size_t count )
;
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Copies the value static_cast < unsigned char > (ch) into each of the first count characters of the object pointed to by dest. If the object is a potentially-overlapping subobject or is not TriviallyCopyable (e.g., scalar, C-compatible struct, or an array of trivially copyable type), the behavior is undefined. If count is greater than the size of the object pointed to by dest
Parameters
| dest | - | pointer to the object to fill |
| ch | - | fill byte |
| count | - | number of bytes to fill |
Return value
dest
Notes
std::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 (e.g., gcc bug 8537
Solutions for that include std::fill with volatile pointers, (C23)
memset_explicit(), (C11)
memset_s, FreeBSD explicit_bzero or Microsoft SecureZeroMemory
Example
#include <bitset> #include <climits> #include <cstring> #include <iostream> int main() { int a[4]; using bits = std::bitset<sizeof(int) * CHAR_BIT>; std::memset(a, 0b1111'0000'0011, sizeof a); for (int ai : a) std::cout << bits(ai) << '\n'; }
Output:
00000011000000110000001100000011 00000011000000110000001100000011 00000011000000110000001100000011 00000011000000110000001100000011
See also
| copies one buffer to another (function) |
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| moves one buffer to another (function) |
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| copies the given wide character to every position in a wide character array (function) |
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| copy-assigns the given value to every element in a range (function template) |
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| copy-assigns the given value to N elements in a range (function template) |
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(C++11)
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checks if a type is trivially copyable (class template) |
C documentation for memset
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