[Bug c++/14507] New: [3.1/3.2/3.2.2/3.2.3/3.3.2/3.3.3 Regression From 2.95.2/2.95.3] Wacky Template ICE

[Bug c++/14507] New: [3.1/3.2/3.2.2/3.2.3/3.3.2/3.3.3 Regression From 2.95.2/2.95.3] Wacky Template ICE

[stl at caltech dot edu]

This bug was found by John Saalweachter, saalweaj@purdue.edu ; I reduced the 
test case and agreed to submit a PR. I have no clue whether the test case is 
valid or not.

The following test case ICEs when compiled with g++ -c:

template <typename A, typename B = int, typename C = int, typename D = int>
struct c : virtual c<A, B> { };

template <typename A, typename B, typename C>
struct c<A, B, C, int> : c<A, B> {
    c() : c() { }
};

I observe the ICE with:
i686-pc-linux-gnu 3.3.2
sparc-sun-solaris2.7 3.2.3
i686-pc-linux-gnu 3.2.2
i386-redhat-linux 3.2.2
i686-pc-linux-gnu 3.1
i686-pc-linux-gnu 3.2

John Saalweachter observes the ICE with:
i686-pc-linux-gnu 3.3.3
i386-slackware-linux 3.2
i486-slackware-linux 3.2.3 

All of these ICEs occur with no other output. For example, my i686-pc-linux-
gnu 3.3.2 emits:

g++: Internal error: Segmentation fault (program cc1plus)
Please submit a full bug report.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.

I observe a clean compile (no ICE, no complaining) with:
i686-pc-linux-gnu 2.95.3

John Saalweachter also observes a clean compile with:
sparc-sun-solaris2.8 2.95.2

Here are three less reduced test cases that also ICE (on my i686-pc-linux-gnu 
3.3.2; I don't know about other systems for these test cases):

[FIRST]
struct s { };
s foo;

template <typename T, s &i0 = foo, s &i1 = foo, s &i2 = foo>
class c : virtual public c<T, i0> { };

template <typename T, s &i0, s &i1>
class c<T, i0, i1, foo> : public c<T, i0> {
public:
    c (const T &i) : c<T> (i) { }
};

[SECOND]
struct s { };

template <typename T, typename i0 = s, typename i1 = s, typename i2 = s>
class c : virtual public c<T, i0> { };

template <typename T, typename i0, typename i1>
class c<T, i0, i1, s> : public c<T, i0> {
public:
  c (const T &i) : c<T> (i) { }
};

[THIRD]
struct s { };

template <typename A, typename B = s, typename C = s, typename D = s>
struct c : virtual c<A, B> { };

template <typename A, typename B, typename C>
struct c<A, B, C, s> : c<A, B> {
  c(const A &i) : c<A> (i) { }
};

-- 
           Summary: [3.1/3.2/3.2.2/3.2.3/3.3.2/3.3.3 Regression From
                    2.95.2/2.95.3] Wacky Template ICE
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: stl at caltech dot edu
                CC: gcc-bugs at gcc dot gnu 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=14507

[Bug c++/14507] [3.3 Regression] Wacky Template ICE

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-09 19:41 -------
Confirmed, a regression from 2.95.3, note 3.4.0 and the mainline is already fixed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |ice-on-valid-code
      Known to fail|                            |3.0.4 3.3.1 3.2.3
      Known to work|                            |3.4.0 3.5.0 2.95.3
   Last reconfirmed|0000-00-00 00:00:00         |2004-03-09 19:41:54
               date|                            |
            Summary|[3.1/3.2/3.2.2/3.2.3/3.3.2/3|[3.3 Regression] Wacky
                   |.3.3 Regression From        |Template ICE
                   |2.95.2/2.95.3] Wacky        |
                   |Template ICE                |
   Target Milestone|---                         |3.3.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14507

[Bug c++/14507] [3.3 Regression] Wacky Template ICE

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-03-09 20:36 -------
Wow, yes, this _is_ wacky. However, it should be legal. 
 
Not surprisingly, the cause of death of previous compilers is due to 
memory starvation after expanding like a dying star on my machine. What 
happens is that apparently it tries to expand the inheritance tree without 
seeing that there is a partial specialization around. For, if I change the 
example to this: 
----------------- 
template <typename A, typename B = int, typename C = int, typename D = int> 
struct c; 
 
template <typename A, typename B, typename C> 
struct c<A, B, C, int> : c<A, B> { 
    c() : c() { } 
}; 
 
template <typename A, typename B, typename C, typename D> 
struct c : virtual c<A, B> { }; 
---------------- 
then it compiles fine. However, in both cases the code may not be legal 
since the class hierarchy is actually infinite. The only difference between 
seeing the partial specialization and not seeing it is that in one case 
it tries to do all the inheritance with virtual base classes, and in the 
other case with non-virtual ones. 
 
W. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |memory-hog


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14507

[Bug c++/14507] [3.3 Regression] Wacky Template ICE

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-04-01 19:40 -------
My point with the infinite class hierarchy is actually not very good. 
After all, we are just declaring a bunch of templates, not instantiating 
any of them. The actual class hierarchy can only be determined once we 
try to instantiate something, since we may have added further specialization 
later on (after the code shown, which already blows up by itself), which 
may terminate the inheritance hierarchy at some finite point. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14507

[Bug c++/14507] [3.3 Regression] Wacky Template ICE

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.3.4                       |3.3.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14507

[Bug c++/14507] [3.3 Regression] Wacky Template ICE

[reichelt at gcc dot gnu dot org]

------- Additional Comments From reichelt at gcc dot gnu dot org  2004-08-10 19:07 -------
Here's a shorter testcase:

====================================================
template<typename T> struct A : virtual A<T> {};

template<typename T> struct A<T*> : A<T>
{
    A() : A() {}
};
====================================================


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |reichelt at gcc dot gnu dot
                   |                            |org
           Keywords|                            |monitored
      Known to fail|3.0.4 3.3.1 3.2.3           |3.0.4 3.2.3 3.3.1 3.3.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14507