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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.os.linux.advocacy
Subject: Re: More Funny Stuff From C
Date: Wed, 12 Jun 2024 02:43:07 -0000 (UTC)
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On 11 Jun 2024 18:23:28 GMT, rbowman wrote:

> ... I've hit instances using functions
> in legacy code where one const in a function resulted in having to
> spread const around to keep the compiler from whining.

Dennis Ritchie himself pointed out some pitfalls with the “const” concept 
early on. For example, take this standard library routine:

    char *strstr(const char *haystack, const char *needle);

Note that the result is a (non-const) pointer into one of the arguments. 
But the arguments are const! So the function is not typesafe. It was done 
this way so that, if the user passed a pointer into a modifiable string, 
they could get back a pointer they could use to make further 
modifications.

The right solution would have been to create two versions of this routine, 
one with a non-const haystack pointer returning non-const, and another 
with a const haystack pointer, returning const.