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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: How to use a struct with qsort()?
Date: Sat, 26 Oct 2019 16:08:37 -0700
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DFS <nospam@dfs.com> writes:
[...]
> So I try it in my code, to replace a small loop:
>
> int wsvals[26]={0};   (not a char as in previous examples)
> memset(wsvals,0,26);
>
> Doesn't work.  The code compiles (tcc Windows) with no warnings, but it 
> doesn't execute.

I presume it does execute.  It just doesn't do what you wanted it to do.

> Finally on stackoverflow I find this:
> "Note that for memset you have to pass the number of bytes, not the 
> number of elements because this is an old C function:
>
> So I do:  memset(wsvals,0,26 * sizeof(int));
>
> And it works.
>
> Most of the descriptions on the web say memset "is used to fill a block 
> of memory with given/particular value."  No mention of the datatype.
>
> Why do I need to also use sizeof() for an int but not a char?

Because sizeof (char) is 1 by definition.  Given:
    char arr[26];
you could do either
    memset(arr, 0, 26);
or
    memset(arr, 0, 26*sizeof(char));
Both are equivalent.

But given an array of any type that you want to zero-fill, just apply
sizeof to the entire object:
    int wsvals[26];
    memset(wsvals, 0, sizeof wsvals);

Note also that in your example, you already initialized the array:
    int wsvals[26]={0};
so there's no need to call memset.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */