wmemset

Defined in header `<wchar.h>`
wchar_t* wmemset( wchar_t* dest, wchar_t ch, size_t count );		(since C95)

Copies the wide character ch into each of the first count wide characters of the wide character array (or integer array of compatible type) pointed to by dest.

If overflow occurs, the behavior is undefined.

If count is zero, the function does nothing.

Parameters

dest	-	pointer to the wide character array to fill
ch	-	fill wide character
count	-	number of wide characters to fill

Return value

Returns a copy of dest

Notes

This function is not locale-sensitive and pays no attention to the values of the wchar_t objects it writes: nulls as well as invalid wide characters are written too.

Example

Run this code

#include <locale.h>
#include <stdio.h>
#include <wchar.h>
 
int main(void)
{
    wchar_t ar[10] = L"1234567890"; // no trailing null in the array
    wmemset(ar, L'\U0001f34c', 5); // replaces [12345] with the 🍌 bananas
    wmemset(ar + 5, L'蕉', 5); // replaces [67890] with the 蕉 bananas
 
    setlocale(LC_ALL, "en_US.utf8");
    for (size_t n = 0; n < sizeof ar / sizeof *ar; ++n)
        putwchar(ar[n]);
    putwchar(L'\n');
}

Output:

🍌🍌🍌🍌🍌蕉蕉蕉蕉蕉

References

C23 standard (ISO/IEC 9899:2023):

7.29.4.6.2 The wmemset function (p: TBD)

C17 standard (ISO/IEC 9899:2018):

7.29.4.6.2 The wmemset function (p: TBD)

C11 standard (ISO/IEC 9899:2011):

7.29.4.6.2 The wmemset function (p: 439)

C99 standard (ISO/IEC 9899:1999):

7.24.4.6.2 The wmemset function (p: 385)

Language
Headers
Type support
Program utilities
Variadic function support
Error handling
Dynamic memory management
Strings library
Algorithms
Numerics
Date and time utilities
Input/output support
Localization support
Concurrency support (C11)
Technical Specifications
Symbol index

memsetmemset_explicitmemset_s (C23)(C11)	fills a buffer with a character (function)
wmemcpywmemcpy_s (C95)(C11)	copies a certain amount of wide characters between two non-overlapping arrays (function)