[Bug c++/18635] New: use of uninitialised reference accepted in C++ front end

[Bug c++/18635] New: use of uninitialised reference accepted in C++ front end

[ajo at acm dot org]

The following (presumably invalid) code is compiled successfully:

  int main(void) 
  {
      int &a = a;
  
      printf("a = %d\n", a);
      return 0;
  }

albeit with the following warning (if given -Wall -W):

  foo.cc: In function `int main()':
  foo.cc:5: warning: 'a' might be used uninitialized in this function

The generated assembly is as follows:

main()
        1070c:  9d e3 bf 90        save         %sp, -0x70, %sp
        10710:  11 00 00 41        sethi        %hi(0x10400), %o0
        10714:  90 12 23 c0        or           %o0, 0x3c0, %o0 ! 0x107c0
        10718:  40 00 40 54        call         printf
        1071c:  d2 02 40 00        ld           [%o1], %o1
        10720:  81 c7 e0 08        ret          
        10724:  91 e8 20 00        restore      %g0, 0x0, %o0

Given that the reference above is never bound to any valid object, should this
instead error?

Tested on 3.4.0 and 3.4.3 (both behave identically).

-- 
           Summary: use of uninitialised reference accepted in C++ front end
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ajo at acm dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: sparc-sun-solaris2.9
  GCC host triplet: sparc-sun-solaris2.9
GCC target triplet: sparc-sun-solaris2.9


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[llib at computer dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |llib at computer dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-24 19:07 -------
No this is valid code (but undefined):
int &a = a;
a is injected before the equals so the code is about the same as:
int *a = &*a;

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[llib at computer dot org]

------- Additional Comments From llib at computer dot org  2004-11-26 02:56 -------
int &a = a;
i don't believe this is valid code.  i believe g++ should reject the code.
various comp.std.c++ people agree with me.

8.3.2/4 states "[...] A reference shall be initialized to refer to a valid
object or function."

surely a (the right-hand-side) is not a valid object or function since it has
not been initialised, so the code is ill-formed.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-11-26 10:16 -------
Do you have a comp.std.c++ link?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[llib at computer dot org]

------- Additional Comments From llib at computer dot org  2004-11-29 00:54 -------
google groups link to discussion:
<http://groups.google.com/groups?hl=en&lr=&th=6d093e6073eaac16&seekm=fcaee77e.0411251120.6a6ad93b%40posting.google.com&frame=off>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-11-29 11:26 -------
OK, reponening after the thread on comp.std.c++

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635

[Bug c++/18635] use of uninitialised reference accepted in C++ front end

[giovannibajo at libero dot it]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
      Known to fail|                            |2.95 3.0.4 3.2.2 4.0.0
   Last reconfirmed|0000-00-00 00:00:00         |2004-11-29 11:41:17
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18635