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From: Grant Edwards <invalid@invalid.invalid>
Newsgroups: comp.lang.python
Subject: Re: Question about math.pi is mutable
Date: Mon, 9 Nov 2015 14:49:15 +0000 (UTC)
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On 2015-11-08, Marko Rauhamaa <marko@pacujo.net> wrote:
> Grant Edwards <invalid@invalid.invalid>:
>
>> On 2015-11-07, Marko Rauhamaa <marko@pacujo.net> wrote:
>>> "const" is a very ineffective tool that clutters the code and forces
>>> you to sprinkle type casts around your code.
>>
>> But it allows the compiler to warn you if you pass a pointer to a
>> read-only data to a function that expects a pointer to writable data.
>
> Unfortunately, it doesn't:
>
>========================================================================
> #include <stdio.h>
> #include <string.h>
>
> int main()
> {
>     const char name[] = "Tom";
>     char *p = strstr(name, "Tom");
>     strcpy(p, "Bob");
>     printf("name = %s\n", name);
>     return 0;
> }
>========================================================================
>
>     $ cc -o prog prog.c
>     $ ./prog
>     Bob
>
> No warning.

Yes, there are ways to fool the compiler by converting a const char*
to a plain char* like you did with strstr().  But in my experience
there are plenty of cases where it will generate a useful warning.

> Point is, the consequences of "proper" use of const are so annoying
> even standard library functions would rather grossly abuse it than
> tolerate compiler warnings everywhere.

That's your opinion.

My differs: _I_ find it useful.  I don't have that many problems with
it.  If you don't like it, don't use it -- nobody is forcing you to
declare 'const' variables. 

-- 
Grant