------- Comment #2 from pinskia at gmail dot com 2010-04-24 23:12 -------
Subject: Re: New: warning attached to a function is emitted even though the
function is not being called
It is called directly because safe_close's value is replaced in the
indirect call. Since safe_close is static and not changed in the code
at all, it is marked as read only and the initialized value can be
used directly.
Sent from my iPhone
On Apr 24, 2010, at 3:49 PM, "bruno at clisp dot org" <gcc-bugzi...@gcc.gnu.org
> wrote:
> The gcc documentation, section "Declaring Attributes of Functions",
> states
> about the __attribute__ ((__warning__ ("..."))) of a function:
> "If this attribute is used on a function declaration and a call to
> such a function is not eliminated through dead code elimination or
> other optimizations, a warning which will include MESSAGE will be
> diagnosed."
>
> Here is a case where the warning is diagnosed although the program
> contains
> no direct call to the function:
> =========================== main.cc ===========================
> extern "C" int close(int);
> static int (*safe_close) (int fd) = close;
> extern __typeof__ (close) close __attribute__ ((__warning__ ("The
> symbol close
> refers to the system function. Use safe_close instead.")));
> int fd;
> int main()
> {
> safe_close(fd);
> }
> ===============================================================
> $ g++ -S -O main.cc
> main.cc: In function 'int main()':
> main.cc:7:17: warning: call to 'close' declared with attribute
> warning: The
> symbol close refers to the system function. Use safe_close instead.
>
> The warning is not justified, because its only use is as initializer
> of the variable 'safe_close', and at that moment, the warning is not
> yet
> attached to it.
>
> Notes:
> - The warning occurs only with optimization, not with -O0.
> - The warning occurs only if the variable 'safe_close' is 'static',
> not
> when it is changed to a global variable.
> - The behaviour of GCC 4.3.4 and GCC 4.4.3 is the same as the one
> of GCC
> 4.5.0.
>
>
> --
> Summary: warning attached to a function is emitted even
> though
> the function is not being called
> Product: gcc
> Version: 4.5.0
> Status: UNCONFIRMED
> Severity: normal
> Priority: P3
> Component: c++
> AssignedTo: unassigned at gcc dot gnu dot org
> ReportedBy: bruno at clisp dot org
> GCC build triplet: i686-pc-linux-gnu
> GCC host triplet: i686-pc-linux-gnu
> GCC target triplet: i686-pc-linux-gnu
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881
