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Re: Allocate length of word vs fixed length

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On 2021-07-19, dfs <nospam@dfs.com> wrote:
> On 7/19/21 5:11 PM, Ike Naar wrote:
>> On 2021-07-19, dfs <nospam@dfs.com> wrote:
>>> 		//different memory allocations
>>> 		if(memoption==1)
>>> 		{memlen=strlen(word);}
>> 
>> /* allocate one extra for the terminating null character */
>>                   memlen = strlen(word) + 1;
>
>
> I did it right.  Look a few lines up (you snipped it)
>
> strcpy(word,rtrim(wordin));
>
> So 'word' already has the nul.

Yes, 'word' has the null. And later on, 'word' is strcpy-ed into
words[i], so you want words[i] to have room for the copy
of 'word', including the terminating null character.

>
>
>
>>> 		else
>>> 		{memlen=maxlen;}
>>> 		
>>> 		words[i] = malloc(sizeof(char*) * memlen);
>
> This works.

It works by luck, not by design.

Suppose 'word' contains the 6-character text "potato".
To store this in words[i], 7 bytes are needed (6 for the 
text plus 1 for the terminating null character).

Now suppose sizeof (char*) equals 8 (a common value for a 64-bit system).
Using malloc(sizeof(char*) * memlen) with memlen=6, 8*6 = 48 bytes are allocated
which is more than enough to store the 7 bytes.

But it would be more memory-efficient to allocate 1*7 = 7 bytes.
Hence the malloc(sizeof (char) * memlen) with memlen=7.

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Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 12:50 -0400
  Re: Allocate length of word vs fixed length Bart <bc@freeuk.com> - 2021-07-19 19:01 +0100
    Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 14:29 -0400
      Re: Allocate length of word vs fixed length Bart <bc@freeuk.com> - 2021-07-19 19:49 +0100
        Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 18:01 -0400
          Re: Allocate length of word vs fixed length Bart <bc@freeuk.com> - 2021-07-19 23:25 +0100
      Re: Allocate length of word vs fixed length scott@slp53.sl.home (Scott Lurndal) - 2021-07-19 20:00 +0000
        Re: Allocate length of word vs fixed length Branimir Maksimovic <branimir.maksimovic@gmail.com> - 2021-07-19 23:29 +0000
      Re: Allocate length of word vs fixed length Real Troll <real.troll@trolls.com> - 2021-07-20 00:30 +0100
        Re: Allocate length of word vs fixed length DFS <nospam@dfs.com> - 2021-07-19 20:40 -0400
          Re: Allocate length of word vs fixed length Real Troll <real.troll@trolls.com> - 2021-07-20 17:00 +0000
      Re: Allocate length of word vs fixed length Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-24 01:07 +0000
  Re: Allocate length of word vs fixed length David Brown <david.brown@hesbynett.no> - 2021-07-19 21:35 +0200
    Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 18:02 -0400
  Re: Allocate length of word vs fixed length Ike Naar <ike@rie.sdf.org> - 2021-07-19 21:11 +0000
    Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 18:03 -0400
      Re: Allocate length of word vs fixed length Ike Naar <ike@sdf.org> - 2021-07-20 05:28 +0000
  Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 18:21 -0400
    Re: Allocate length of word vs fixed length Bart <bc@freeuk.com> - 2021-07-19 23:29 +0100
      Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-19 18:40 -0400
  Re: Allocate length of word vs fixed length Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2021-07-20 11:44 +1000
  Re: Allocate length of word vs fixed length Real Troll <real.troll@trolls.com> - 2021-07-20 22:15 +0000
    Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-20 20:22 -0400
      Re: Allocate length of word vs fixed length dfs <nospam@dfs.com> - 2021-07-21 23:23 -0400

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