[PR44629] internal compiler error in unify

[stestagg]

Binary package hint: gcc-4.3

Trying to compile the attached, preprocessed, source gives the error:

../aclib/aclib.cpp: In function ‘void ac_print_dot(acSearcher*)’:
../aclib/aclib.cpp:35: internal compiler error: in unify, at cp/pt.c:13439
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-4.3/README.Bugs> for instructions.

GCC version:

Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.3.3-5ubuntu4' --with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr --enable-targets=all --with-tune=generic --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4)

on Ubuntu 9.04

[stestagg (stestagg)]

Also happens on gcc-snapshot

Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 20090327-0ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-snapshot/README.Bugs --enable-languages=c,c++,java,fortran,objc,obj-c++,ada --prefix=/usr/lib/gcc-snapshot --enable-shared --enable-multiarch --with-system-zlib --disable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-java-awt=gtk --enable-gtk-cairo --disable-plugin --with-java-home=/usr/lib/gcc-snapshot/java-1.5.0-gcj-4.4-1.5.0.0/jre --enable-java-home --with-jvm-root-dir=/usr/lib/gcc-snapshot/jvm --with-jvm-jar-dir=/usr/lib/gcc-snapshot/jvm-exports --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-mpfr --enable-targets=all --disable-werror --with-tune=generic --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.4.0 20090327 (experimental) [trunk revision 145121] (Ubuntu 20090327-0ubuntu1)

sstagg@sphinx:~/src/acSearch/aclibtest$ g++ aclib.i
../aclib/aclib.cpp: In function 'void ac_print_dot(acSearcher*)':
../aclib/aclib.cpp:35: internal compiler error: in unify, at cp/pt.c:13924
Please submit a full bug report,

[Matthias Klose (doko)]

seen with 4.3, 4.4, 4.5, 4.6

$ gcc-4.5 -c aclib.ii
../aclib/aclib.cpp: In function 'void ac_print_dot(acSearcher*)':
../aclib/aclib.cpp:35:61: internal compiler error: in unify, at cp/pt.c:15155
Please submit a full bug report,
with preprocessed source if appropriate.

[Matthias Klose (doko)]

Created attachment 20976
preprocessed source

[Matthias Klose (doko)]

seen with 4.4 and 4.5 too

[Rguenth (rguenth)]

Confirmed.

../aclib/aclib.cpp(35): error: no instance of function template "ACSearch::Grapher::simple_output" matches the argument list
            argument types are: (acSearcher)
    std::basic_string<char> output = Grapher::simple_output(*s);
                                     ^
Reduced testcase for the ICE:

template<typename _CharT> struct char_traits;
namespace __gnu_cxx __attribute__ ((__visibility__ ("default"))) {
    template<typename _Tp> class new_allocator { };
}
namespace std __attribute__ ((__visibility__ ("default"))) {
    template<typename _Tp>
    class allocator: public __gnu_cxx::new_allocator<_Tp> { };
    template<typename _CharT, typename _Traits = char_traits<_CharT>, typename _Alloc = allocator<_CharT> > class basic_string;
    template<typename _CharT, typename _Traits, typename _Alloc>
    class basic_string {
    };
}
template<typename T> int eq_cmp(T a, T b){ }
template<typename T> int unsafe_case_cmp(T a, T b){ }
template<typename T, int (*cmp_fn)(T, T) = eq_cmp> class Searcher{ };
class Grapher{
    template <typename T>
    static std::basic_string<T> simple_output(Searcher<T> &sch){ }
};
typedef Searcher<char, unsafe_case_cmp> acSearcher;
void ac_print_dot(acSearcher *s){
    std::basic_string<char> output = Grapher::simple_output(*s);
}

[Jakub-gcc (jakub-gcc)]

3.4 gives here:
pr44629.C:23: sorry, unimplemented: use of `overload' in template type unification
pr44629.C:23: error: no matching function for call to `Grapher::simple_output(Searcher<char, unsafe_case_cmp [with T = char]>&)'
 int unsafe_case_cmp(T, T) [with T = char]

So it is a regression.

[Jason-gcc (jason-gcc)]

Same ICE on valid testcase:

template<typename T> int cmp1(T a, T b);
template<typename T> int cmp2(T a, T b);
template<typename T, int (*cmp)(T, T) = cmp1> struct A { };
template <typename T> void f (A<T> &);
void g()
{
  A<char> a;
  f(a);
}

though 3.4 didn't accept it, it gave the same sorry, so it isn't a big regression.

[Jason-gcc (jason-gcc)]

Created attachment 23550
WIP patch to accept my testcase

Here's a patch that makes my testcase work. I don't want to put it in 4.6 because it produces mangling different from the EDG compiler, and want to clarify how it should mangle first.

[Jason-gcc (jason-gcc)]

Created attachment 23551
WIP patch to make the testcase sorry as before

And here's a patch that just restores the previous sorry behavior. Do you think it's worth applying this to 4.6?

[Jason-gcc (jason-gcc)]

A middle ground would be to fix the bug in unify without adding mangling support, so we get the sorry there. I guess I'll do that.

[Jason-gcc (jason-gcc)]

Author: jason
Date: Wed Mar 9 17:57:46 2011
New Revision: 170824

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170824
Log:
 PR c++/44629
 * pt.c (unify): An unresolved overload is a nondeduced context.

Added:
    trunk/gcc/testsuite/g++.dg/template/nontype22.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Jason-gcc (jason-gcc)]

Author: jason
Date: Wed Mar 9 17:57:48 2011
New Revision: 170825

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170825
Log:
 PR c++/44629
 * pt.c (unify): An unresolved overload is a nondeduced context.

Added:
    branches/gcc-4_4-branch/gcc/testsuite/g++.dg/template/nontype22.C
Modified:
    branches/gcc-4_4-branch/gcc/cp/ChangeLog
    branches/gcc-4_4-branch/gcc/cp/pt.c
    branches/gcc-4_4-branch/gcc/testsuite/ChangeLog

[Jason-gcc (jason-gcc)]

Author: jason
Date: Wed Mar 9 17:57:51 2011
New Revision: 170826

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170826
Log:
 PR c++/44629
 * pt.c (unify): An unresolved overload is a nondeduced context.

Added:
    branches/gcc-4_5-branch/gcc/testsuite/g++.dg/template/nontype22.C
Modified:
    branches/gcc-4_5-branch/gcc/cp/ChangeLog
    branches/gcc-4_5-branch/gcc/cp/pt.c
    branches/gcc-4_5-branch/gcc/testsuite/ChangeLog

[Jason-gcc (jason-gcc)]

ICE fixed in 4.4, 4.5, 4.6. Not worth applying to 4.3 at this point I think.

[Bangerth (bangerth)]

(In reply to comment #4)
> template<typename T> int cmp1(T a, T b);
> template<typename T> int cmp2(T a, T b);
> template<typename T, int (*cmp)(T, T) = cmp1> struct A { };

I'm confused why this would be an overload set. cmp1 is a template so I
can't see how this code would even begin to be valid without specifying
the template argument in the default argument...

W.

[Jason-gcc (jason-gcc)]

(In reply to comment #12)
> I'm confused why this would be an overload set. cmp1 is a template so I
> can't see how this code would even begin to be valid without specifying
> the template argument in the default argument...

Once you know A's T, you have a desired type int (*)(T, T) from which to determine which specialization of the template to use.

[Bangerth (bangerth)]

(In reply to comment #13)
> Once you know A's T, you have a desired type int (*)(T, T) from which to
> determine which specialization of the template to use.

Hm, I agree that the type could be deduced. I could nevertheless
have sworn that this should be invalid:
..........................
template <typename T> int cmp1(T a, T b);
int (*cmp)(int, int) = cmp1;
...........................
But it compiles in fact.

I had no idea a template name could be implicitly instantiated in this
context. Thanks for educating me!

Best
 W.