[Bug c++/23789] New: compilation error when template parameters have certain complexity

[Bug c++/23789] New: compilation error when template parameters have certain complexity

[andres_takach at mentor dot com]

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While 3.4 made substantial improvements on handling of template parameters,
there are still some incorrect compiler errors that are triggered with a
combination of complexity in the template arguments and levels of templates. 

In the testcase below, gcc will error out with:

  t.cxx: In function ‘void foo_function(ch_t, ch_t, ch_t*)’:
  t.cxx:20: error: ‘(((int)false) + 7)’ is not a valid template argument for
type ‘int’ because it is a non-constant expression
  t.cxx:20: error: no match for ‘operator+’ in ‘A + B’

The error goes away if the function foo_function (that calls the
my_int::operator +) is un-templatized. Note that the template parameter for
foo_function is not even used anywhere in the function so it should have no
impact. Simplifying the expression for the template parameters on the return
type of my_int::operator + also makes the error go away.


#define MAX(a,b) ((a) > (b) ? (a) : (b))
                                                                               
                                                                    
template<int W, bool S>
class mc_int {
public:
  int d;
  mc_int() { d = 0; }
  mc_int(int x) { d = x; }
  mc_int(const mc_int &x) { d = x.d; }
  template<int W2, bool S2>
  mc_int<MAX(W+(S2&&!S),W2+(S&&!S2))+1, (S||S2)> operator +(const mc_int<W2,S2>
& x) const {
    return 0;
  }
};
                                                                               
                                                                    
typedef mc_int<6,false> ch_t;
                                                                               
                                                                    
template <int footemplate>
void foo_function(ch_t A, ch_t B, ch_t *C) {
    A + B;
}
                                                                               
                                                                    
int main() {
  ch_t fooA, fooB, fooC, fooD, fooE;
  fooA= (ch_t) 5;
  fooB= (ch_t) 15;
  ch_t CC;
  foo_function<0>(fooA, fooB, &CC);
}

-- 
           Summary: compilation error when template parameters have certain
                    complexity
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: andres_takach at mentor dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: gcc version 4.0.1
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] compilation error when template parameters have certain complexity

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |4.0.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
      Known to fail|                            |3.4.0 4.0.0 4.1.0
      Known to work|                            |3.3.3
            Summary|compilation error when      |[3.4/4.0/4.1 Regression]
                   |template parameters have    |compilation error when
                   |certain complexity          |template parameters have
                   |                            |certain complexity
   Target Milestone|---                         |4.0.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[andres_takach at mentor dot com]

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------- Additional Comments From andres_takach at mentor dot com  2005-09-09 02:37 -------
t.ii file:

# 1 "t.cxx"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "t.cxx"
                                                                               
                                                                    
                                                                               
                                                                    
template<int W, bool S>
class mc_int {
public:
  int d;
  mc_int() { d = 0; }
  mc_int(int x) { d = x; }
  mc_int(const mc_int &x) { d = x.d; }
  template<int W2, bool S2>
  mc_int<((W+(S2&&!S)) > (W2+(S&&!S2)) ? (W+(S2&&!S)) : (W2+(S&&!S2)))+1,
(S||S2)> operator +(const mc_int<W2,S2> & x) const {
    return 0;
  }
};
                                                                               
                                                                    
typedef mc_int<6,false> ch_t;
                                                                               
                                                                    
template <int footemplate>
void foo_function(ch_t A, ch_t B, ch_t *C) {
    A + B;
}
                                                                               
                                                                    
int main() {
  ch_t fooA, fooB, fooC, fooD, fooE;
  fooA= (ch_t) 5;
  fooB= (ch_t) 15;
  ch_t CC;
  foo_function<0>(fooA, fooB, &CC);
}

---------------------------------------------------------------------
Output generated with "c++ -v -save-temps t.cxx":
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with:
/user/jasong/hdl/sb/sim/dcs_gcc/ixl/build/src/gcc-4.0.1/configure
--prefix=/user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1
--enable-languages=c,c++
Thread model: posix
gcc version 4.0.1 (Mentor-DCS)
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/libexec/gcc/i686-pc-linux-gnu/4.0.1/cc1plus -E -quiet -v -D_GNU_SOURCE t.cxx -mtune=pentiumpro -fpch-preprocess -o t.ii
ignoring nonexistent directory
"/user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/lib/gcc/i686-pc-linux-gnu/4.0.1/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/lib/gcc/i686-pc-linux-gnu/4.0.1/../../../../include/c++/4.0.1
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/lib/gcc/i686-pc-linux-gnu/4.0.1/../../../../include/c++/4.0.1/i686-pc-linux-gnu
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/lib/gcc/i686-pc-linux-gnu/4.0.1/../../../../include/c++/4.0.1/backward
 /usr/local/include
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/include
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/lib/gcc/i686-pc-linux-gnu/4.0.1/include
 /usr/include
End of search list.
 /user/jasong/hdl/sb/sim/dcs_gcc/ixl/exports/mgc_home/pkgs/dcs_gcc.ixl/gcc-4.0.1/libexec/gcc/i686-pc-linux-gnu/4.0.1/cc1plus -fpreprocessed t.ii -quiet -dumpbase t.cxx -mtune=pentiumpro -auxbase t -version -o t.s
GNU C++ version 4.0.1 (Mentor-DCS) (i686-pc-linux-gnu)
        compiled by GNU C version 3.4.3 (Mentor-DCS).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
t.cxx: In function ‘void foo_function(ch_t, ch_t, ch_t*)’:
t.cxx:20: error: ‘(((int)false) + 7)’ is not a valid template argument for type
‘int’ because it is a non-constant expression
t.cxx:20: error: no match for ‘operator+’ in ‘A + B’



-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|3.3.3                       |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-09 02:39 -------
Confirmed, reduced testcase:
#define MAX(a,b) ((a) > (b) ? (a) : (b))
template<int W, bool S>
class mc_int {
  template<int W2, bool S2>
  mc_int<MAX(W+(S2&&!S),W2+(S&&!S2))+1, false> operator +(const mc_int<W2,S2>& x) const;
};
typedef mc_int<6,false> ch_t;
template <int footemplate>
void foo_function(ch_t A, ch_t B, ch_t *C)
{
    A + B;
}

Note changing foo_function to a non template, makes this work.

This is caused by not folding in templates.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
  GCC build triplet|gcc version 4.0.1           |
   GCC host triplet|i686-pc-linux-gnu           |
 GCC target triplet|i686-pc-linux-gnu           |
      Known to work|                            |3.3.3
   Last reconfirmed|0000-00-00 00:00:00         |2005-09-09 02:39:23
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2005-09-09 14:06 -------
This is weird indeed. Here's the shortest I can come up with: 
------------------- 
template <int W> struct X { 
  template <int W2> 
  X< (W+(W&&W) > 1 ? W+(W&&W) : 1)+1> 
  operator + (const X<W2>&) const; 
}; 
 
template <int dummy> void foo() 
{ 
  X<6> A,B; 
  A + B; 
} 
----------------------------- 
The expression in the return type isn't fully folded, as Andrew noted: 
 
g/x> /home/bangerth/bin/gcc-4.1-pre/bin/c++ -c x.cc 
x.cc: In instantiation of &#8216;X<6>&#8217;: 
x.cc:10:   instantiated from here 
x.cc:4: error: &#8216;(((int)true) + 7)&#8217; is not a valid template argument for type 
&#8216;int&#8217; because it is a non-constant expression 
x.cc: In function &#8216;void foo()&#8217;: 
x.cc:10: error: no match for &#8216;operator+&#8216; in &#8216;A + B&#8216; 
 
Weird enough, however, is that if I rename operator+ into a regular member 
function, then things work just fine. Somebody's gotta explain this to me... 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2005-09-09 16:58 -------
The problem here is that the NOP_EXPR case in tsubst is implemented by
build_nop, which unconditionally adds a NOP_EXPR.  We need to simplify the
NOP_EXPR away so that fold can do its job.  Perhaps we should have a CAST_EXPR
here, rather than a NOP_EXPR.  I'll work it out.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |mark at codesourcery dot com
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-09-12 22:38 -------
Subject: Bug 23789

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	mmitchel@gcc.gnu.org	2005-09-12 22:38:34

Modified files:
	gcc/cp         : ChangeLog cvt.c pt.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/template: nontype14.C 

Log message:
	PR c++/23789
	* cvt.c (perform_qualification_conversions): Don't create
	unnecessary NOP_EXPRs.
	* pt.c (tsubst_template_arg): Use fold_non_dependent_expr.
	
	PR c++/23789
	* g++.dg/template/nontype14.C: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4885&r2=1.4886
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/cvt.c.diff?cvsroot=gcc&r1=1.186&r2=1.187
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/pt.c.diff?cvsroot=gcc&r1=1.1032&r2=1.1033
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.6050&r2=1.6051
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/nontype14.C.diff?cvsroot=gcc&r1=NONE&r2=1.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-09-12 22:39 -------
Subject: Bug 23789

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-4_0-branch
Changes by:	mmitchel@gcc.gnu.org	2005-09-12 22:39:33

Modified files:
	gcc/cp         : ChangeLog cvt.c pt.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/template: nontype14.C 

Log message:
	PR c++/23789
	* cvt.c (perform_qualification_conversions): Don't create
	unnecessary NOP_EXPRs.
	* pt.c (tsubst_template_arg): Use fold_non_dependent_expr.
	
	PR c++/23789
	* g++.dg/template/nontype14.C: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.4648.2.99&r2=1.4648.2.100
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/cvt.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.180.6.1&r2=1.180.6.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/pt.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.978.2.23&r2=1.978.2.24
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.5084.2.399&r2=1.5084.2.400
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/nontype14.C.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=NONE&r2=1.1.2.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789

[Bug c++/23789] [3.4/4.0/4.1 Regression] compilation error when template parameters have certain complexity

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2005-09-12 22:43 -------
Fixed in 4.0.2.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789