Path: csiph.com!eternal-september.org!feeder.eternal-september.org!reader01.eternal-september.org!.POSTED!not-for-mail
From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: does char *str="abcd"; alloc addressable memory?
Date: Thu, 09 Jul 2020 10:13:20 -0700
Organization: A noiseless patient Spider
Lines: 41
Message-ID: <86fta0fw7j.fsf@linuxsc.com>
References: <rdv1l5$clo$1@reader1.panix.com> <rdv1vh$idl$1@dont-email.me> <87k0zgbiwt.fsf@nosuchdomain.example.com> <re0oqg$4kj$3@reader1.panix.com> <re18kf$2v2$1@dont-email.me> <6HCNG.37756$bQ4.31924@fx04.iad>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Injection-Info: reader02.eternal-september.org; posting-host="c87a676e1fef5793b5d15a831e4eb134"; logging-data="30408"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+WIawVxVmaCJLmqN/DYz0vJSl0nVJZpB0="
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux)
Cancel-Lock: sha1:9SSRt7a03vqOFOHAPY7VAkHrPvo= sha1:cNcD88rOWkbwu/343+bnDBYvltQ=
Xref: csiph.com comp.lang.c:153163

Richard Damon <Richard@Damon-Family.org> writes:

> On 7/7/20 3:35 AM, David Brown wrote:
>
>> On 07/07/2020 05:05, John Forkosh wrote:
>>
>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
>>>
>>>> <snip>
>>>> Some compilers have non-conforming options to treat string literals as
>>>> const.  (gcc has "-Wwrite-strings".)
>>>
>>> Wasn't aware of that warning, and sure enough...
>>>    bash-5.0$ cc -Wwrite-strings tester.c -o tester
>>>    tester.c:  In function 'main':
>>>    tester.c:7:15: warning: initialization discards 'const' qualifier
>>>                   from pointer target type [-Wdiscarded-qualifiers]
>>>     7 |   char *str = ( argc>1? argv[1] : "01234&56789" );
>>>       |               ^
>>> And (as suggested downthread) changing line 7 to
>>>    char *str = ( argc>1? argv[1] :  (char *)"01234&56789" );
>>> eliminates the warning, but the program still segfaults.
>>>
>>> So, the really nice -switch would be one that reverts to the
>>> classical behavior where "string literals" aren't const.
>>> Any way to do that?
>>
>> What do you mean by "classical behaviour" ?  Writing to string literals
>> has been undefined behaviour since C was standardised, and AFAIK it was
>> not explicitly allowed in pre-standard C.
>>
>> You can't expect a switch to allow something that has been considered an
>> extremely bad idea since the beginnings of C !
>
> My memory was that in the 80s, there were implementations that defined
> that it would work, and implementation definitions has always been the
> highest authority, when working on that implementation.

Much more recently than that, gcc had an option -fwriteable-strings.
That option has since been removed, but it was still available in
the last ten years or so.