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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: declarator |
| Date | 2015-06-30 08:22 -0700 |
| Organization | None to speak of |
| Message-ID | <lnfv592pbv.fsf@kst-u.example.com> (permalink) |
| References | (3 earlier) <p2c3pa578rsfhdkfq2olp0bb9vq710lfec@4ax.com> <mmsocv$eqk$1@dont-email.me> <lnk2um2bv7.fsf@kst-u.example.com> <mmstuk$ldj$1@dont-email.me> <t434pahgvcplooij8kdp6kfap4u52bb430@4ax.com> |
Barry Schwarz <schwarzb@dqel.com> writes:
[...]
>>"Keith Thompson" <kst-u@mib.org> wrote in message
>>news:lnk2um2bv7.fsf@kst-u.example.com...
>>> "Bill Cunningham" <nospam@nspam.invalid> writes:
[...]
>>>> p.c: In function 'main':
>>>> p.c:8:8: warning: assignment makes pointer from integer without a cast
>>>> [enabled by default]
>>>> pf = print("hello there");
>>>> ^
>>>> p.c:9:5: warning: return makes integer from pointer without a cast
>>>> [enabled
>>>> by default]
>>>> return pf;
>>>> ^
>>>>
>>>> I did not use -Wall either. as the compiler says "enabled by default. It
>>>> compiles and runs.
>
> It compiles with diagnostics which you have chosen to ignore
> (something that should not be done unless you have a VERY THOROUGH
> understanding of what the diagnostic means) and APPEARS to run. Since
> you don't know what you want to do, you have no idea if the code
> accomplished same. Given that you ended up assigning an int 0 to a
> pointer (making the pointer a NULL pointer which does not point
> anywhere), any subsequent attempt to use the pointer to actually call
> a function would have failed. Please tell us this was not your goal.
Storing a null pointer in pf is the most likely consequence of assigning
the int value 0 to pf, but it's not the only possibility. There is no
implicit conversion from int to a pointer type -- other than the special
case of a *constant* expression with the value 0, which is a null
pointer constant. Even an explicit conversion (a cast) from an integer
0 to a pointer does not necessarily yield a null pointer though it
commonly does.
The assignment is a constraint violation. A compiler
can simply reject it. If it chooses to accept it the behavior is undefined.
>>> gcc has an unfortunate habit of issuing non-fatal warnings for code that
>>> is unambiguously incorrect.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-28 21:58 -0400
declarator "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-28 19:14 -0700
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-28 22:36 -0400
Re: declarator "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-06-28 19:46 -0700
Re: declarator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-29 11:22 +0100
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-29 16:07 -0400
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-29 16:09 -0400
Re: declarator Barry Schwarz <schwarzb@dqel.com> - 2015-06-28 21:51 -0700
Re: declarator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-29 11:08 +0100
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-29 16:18 -0400
Re: declarator Barry Schwarz <schwarzb@dqel.com> - 2015-06-29 14:23 -0700
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-29 18:39 -0400
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-29 20:39 -0400
Re: declarator Keith Thompson <kst-u@mib.org> - 2015-06-29 19:01 -0700
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-29 22:13 -0400
Re: declarator Barry Schwarz <schwarzb@dqel.com> - 2015-06-29 20:45 -0700
Re: declarator Keith Thompson <kst-u@mib.org> - 2015-06-30 08:22 -0700
Re: declarator Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 08:44 -0700
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-06-30 12:48 -0400
Re: declarator Barry Schwarz <schwarzb@dqel.com> - 2015-06-30 15:32 -0700
Re: declarator John Bode <jfbode1029@gmail.com> - 2015-07-01 13:50 -0700
Re: declarator gazelle@shell.xmission.com (Kenny McCormack) - 2015-07-01 21:57 +0000
Re: declarator "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-01 15:05 -0700
Re: declarator "Bill Cunningham" <nospam@nspam.invalid> - 2015-07-02 20:34 -0400
Re: declarator Jens Stuckelberger <Jens_Stuckelberger@nowhere.net> - 2015-06-29 14:55 +0000
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