[Bug c/43728] New: Warning for redundant static function prototypes

[Bug c/43728] New: Warning for redundant static function prototypes

[jakub at gcc dot gnu dot org]

Prototypes for static functions that aren't used in between the prototype and
the actual static function definition are useless and could be cleaned up, I
think gcc itself has thousands of such useless prototypes.

It isn't hard to add a warning for this.  Given:
static void foo (int);

#ifdef D
void bar (void)
{
  foo (0);
}
#endif

static void foo (int x)
{
  x++;
}

void baz (void)
{
  foo (0);
}

we'd warn about the foo prototype (unless compiling with -DD).


-- 
           Summary: Warning for redundant static function prototypes
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[jakub at gcc dot gnu dot org]

------- Comment #1 from jakub at gcc dot gnu dot org  2010-04-12 15:14 -------
Created an attachment (id=20367)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20367&action=view)
gcc46-pr43728.patch

Quick patch, so far without documentation and testsuite and almost untested.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[jakub at gcc dot gnu dot org]

------- Comment #2 from jakub at gcc dot gnu dot org  2010-04-12 15:16 -------
*** Bug 36195 has been marked as a duplicate of this bug. ***


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eugene dot zelenko at gmail
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[manu at gcc dot gnu dot org]

------- Comment #3 from manu at gcc dot gnu dot org  2010-04-12 15:38 -------
If you are going to add such a warning, please be more explicit. I suggest:

"redundant prototype for static function %qD because it is never used before
its definition"


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manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[jason at gcc dot gnu dot org]

------- Comment #4 from jason at gcc dot gnu dot org  2010-04-12 16:16 -------
...and then after removing the prototype, compiling with -DD would fail.  I
don't object to having such a flag, but I don't think we want it in -Wall.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[jakub at gcc dot gnu dot org]

------- Comment #5 from jakub at gcc dot gnu dot org  2010-04-12 16:29 -------
-Wredundant-decls is a non-default warning already, not enabled with -Wall nor
-W and I certainly don't want to enable it by default.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2010-04-14 16:06 -------
Created an attachment (id=20378)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20378&action=view)
gcc46-pr43728.patch

Updated patch.  There are still cases I'm unsure about.  E.g. for:

static void g ();

void f()
{
  void g();
  g();
}

void g()
{
}

int main () {
  f ();
}

with -Wredundant-decls=2 in C we complain (even with -Wredundant-decls alone
and before the patch) that void g(); in f function is redundant declaration,
but in C++ we don't and instead with -Wredundant-decls=2 the warning newly
diagnoses
the first static void g (); prototype as redundant (in this case it isn't,
because it affects whether void g (); in the subroutine is static or not).
Not sure why TREE_USED isn't set in C++ case during the g call in f, Jason?


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jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #20367|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728

[Bug c/43728] Warning for redundant static function prototypes

[jason at gcc dot gnu dot org]

------- Comment #7 from jason at gcc dot gnu dot org  2010-04-14 20:26 -------
Presumably TREE_USED isn't set on the global declaration because the call uses
the local one.  And the local declaration might not be redundant if the
programmer is using it to suppress argument-dependent lookup.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43728