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
