[Bug c++/28262] New: Inconsistent "default arguments are only permitted for function parameters".

[Bug c++/28262] New: Inconsistent "default arguments are only permitted for function parameters".

[jason dot cipriani at gmail dot com]

Description:

  g++ appears to have issues when declaring function pointer types that accept
default function parameters. However it does not have issues when declaring
non-pointer function types that accept default function parameters. For
example, the following code:

  typedef void (* funcptr) (int = 10);

  Produces the error "default arguments are only permitted for function
parameters". However, a "workaround" for this exists. The following code
compiles without problems, and the default parameter works:

  typedef void (funcptrhack) (int = 10);
  typedef funcptrhack * funcptr;

  I believe this is a bug because a workaround exists, and because of the
inconsistency. Additionally, this problem does not seem to occur on pre-3.4.2
versions of GCC (the next lowest version tested was 3.3.3; not sure where in
that range it started failing). However, I am not sure what the bug is: I
believe that either both of the above examples should succeed or both should
fail.

"Buggy" behavior observed on versions:
  3.4.2 [g++.exe (GCC) 3.4.2 (mingw-special)]
  3.4.3 [specific version unavailable]
  3.4.4 [specific version unavailable]
  3.4.4 [g++ (GCC) 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125)]
  3.4.5 [g++ (GCC) 3.4.5 (Gentoo 3.4.5, ssp-3.4.5-1.0, pie-8.7.9)]
  4.0.3 [Ubuntu 4.0.3-1ubuntu5]

"Working" behavior observed on versions:
  3.2   [g++ (GCC) 3.2 20020903 (Red Hat Linux 8.0 3.2-7)]
  3.2.2 [specific version unavailable]
  3.3.3 [specific version unavailable]

Configuration options unavailable. Some system types and GCC versions
unavailable as indicated above.

Preprocessed output for both cases follows:

---

"Buggy" output, compiled with:

  g++ -W -Wall -pedantic

Preprocessed file:

# 1 "gccbug.cpp"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "gccbug.cpp"

typedef void (* funcptr) (int = 10);

void testfunc (int) {
}

int main (int, char **) {

  funcptr fp = &testfunc;

  (*fp)();
  (*fp)(20);

  return 0;

}

---

"Working" output, compiled with:

  g++ -W -Wall -pedantic

Preprocessed file:

# 1 "gccbug.cpp"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "gccbug.cpp"

typedef void (funcptrhack) (int = 10);
typedef funcptrhack * funcptr;

void testfunc (int) {
}

int main (int, char **) {

  funcptr fp = &testfunc;

  (*fp)();
  (*fp)(20);

  return 0;

}

---

-Jason


-- 
           Summary: Inconsistent "default arguments are only permitted for
                    function parameters".
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jason dot cipriani at gmail dot com
 GCC build triplet: Multiple, see report.
  GCC host triplet: Multiple, see report.
GCC target triplet: Multiple, see report.


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262

[Bug c++/28262] Inconsistent "default arguments are only permitted for function parameters".

[jason dot cipriani at gmail dot com]

------- Comment #2 from jason dot cipriani at gmail dot com  2006-07-05 00:22 -------
Created an attachment (id=11821)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11821&action=view)
"Working" preprocessed source.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262

[Bug c++/28262] Inconsistent "default arguments are only permitted for function parameters".

[jason dot cipriani at gmail dot com]

------- Comment #1 from jason dot cipriani at gmail dot com  2006-07-05 00:22 -------
Created an attachment (id=11820)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11820&action=view)
"Broken" preprocessed source.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262

[Bug c++/28262] Inconsistent "default arguments are only permitted for function parameters".

[jason dot cipriani at gmail dot com]

------- Comment #3 from jason dot cipriani at gmail dot com  2006-07-05 00:23 -------
Apologies for inlining preprocessor output. I have attached the files.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262

[Bug c++/28262] Inconsistent "default arguments are only permitted for function parameters".

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2006-07-05 00:31 -------
Your workaround is really invalid code and should be rejected.
So what we have here is an accepts invalid that is not a regression.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
  GCC build triplet|Multiple, see report.       |
   GCC host triplet|Multiple, see report.       |
 GCC target triplet|Multiple, see report.       |
           Keywords|                            |accepts-invalid
      Known to fail|                            |2.95.3 4.0.0 4.1.0 4.2.0
                   |                            |3.0.4 3.2.3 3.3.3 3.4.0
   Last reconfirmed|0000-00-00 00:00:00         |2006-07-05 00:31:16
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262

[Bug c++/28262] Inconsistent "default arguments are only permitted for function parameters".

[jason dot cipriani at gmail dot com]

------- Comment #5 from jason dot cipriani at gmail dot com  2006-07-05 00:35 -------
Agreed. Wasn't sure if it was actually supposed to work or not.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262

[Bug c++/28262] Inconsistent "default arguments are only permitted for function parameters".

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2006-07-05 00:41 -------
Just a note, the follow patch deprecated them in 3.4:
http://gcc.gnu.org/ml/gcc-patches/2003-07/msg02485.html

Though it seems to miss this part for some reason.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28262