[Bug c++/17763] New: Wrong context in error message for template parameter

[Bug c++/17763] New: Wrong context in error message for template parameter

[solodon at mail dot com]

It seems that in some cases g++ reports in diagnostic messages type names of
template parameters based on the names used in the first instantiation of the
template and not those that appear in the context of the error. Roughly if A,B,X
and Y are all typedef-ed to int, then g++ can report error about incorrect usage
of class T<X,Y> where it has to report incorrect usage of class T<A,B>. Here is
a small application that reproduces this problem in G++ 3.2 and accordingly to
my professor in 3.4:

#include <map>

int main()
{
  typedef int X;
  typedef int Y;
  typedef std::map<X,Y> XYMap; // X and Y happen to be int

  XYMap xy; // This will instantiate std::map<int,int>

  xy[0] = 1;
  
  typedef int A;
  typedef int B;
  
  typedef std::map<A,B>  ABMap;  // A and B also happen to be int
  typedef std::pair<A,B> ABPair;
  
  ABMap  ab;     // Code for this was already instantiated higher!
  ABPair p(0,1); // Pair of A B. Not relevant, required to generate error
  
  ab[0] = 1;
  
  ABMap::iterator q = ab.begin();
  
  // Here we get an error message, because map's value_type is pair<const A, B>
  // and not pair<A, B> as we try to compare it to.
  // BUT: Look which types are reported as types of map's value_type: 
  // they are X and Y which are completely irrelevant to ABMap! 
  // It seems g++ just peeks the type names of the first instantiation with such
  // actual types, which actually generates code for both maps.
  assert(*q == p);

  return 0;
}

Here is what compiler gives when I run it as: gcc -v -save-temps err_rep.cpp

==8<=========================================================================
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --with-system-zlib --enable-__cxa_atexit --host=i386-redhat-linux
Thread model: posix
gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)
 /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/cpp0 -lang-c++ -D__GNUG__=3
-D__DEPRECATED -D__EXCEPTIONS -v -D__GNUC__=3 -D__GNUC_MINOR__=2
-D__GNUC_PATCHLEVEL__=2 -D__GXX_ABI_VERSION=102 -D__ELF__ -Dunix -D__gnu_linux__
-Dlinux -D__ELF__ -D__unix__ -D__gnu_linux__ -D__linux__ -D__unix -D__linux
-Asystem=posix -D__NO_INLINE__ -D__STDC_HOSTED__=1 -D_GNU_SOURCE -Acpu=i386
-Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i386__ err_rep.cpp err_rep.ii
GNU CPP version 3.2.2 20030222 (Red Hat Linux 3.2.2-5) (cpplib) (i386 Linux/ELF)
ignoring nonexistent directory "/usr/i386-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/3.2.2
 /usr/include/c++/3.2.2/i386-redhat-linux
 /usr/include/c++/3.2.2/backward
 /usr/local/include
 /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/include
 /usr/include
End of search list.
 /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/cc1plus -fpreprocessed err_rep.ii
-quiet -dumpbase err_rep.cpp -version -o err_rep.s
GNU CPP version 3.2.2 20030222 (Red Hat Linux 3.2.2-5) (cpplib) (i386 Linux/ELF)
GNU C++ version 3.2.2 20030222 (Red Hat Linux 3.2.2-5) (i386-redhat-linux)
	compiled by GNU C version 3.2.2 20030222 (Red Hat Linux 3.2.2-5).
err_rep.cpp: In function `int main()':
err_rep.cpp:30: no match for `std::pair<const X, Y>& == main()::ABPair&' 
   operator
==8<=========================================================================

Line 30 corresponds to line with assert.

-- 
           Summary: Wrong context in error message for template parameter
           Product: gcc
           Version: 3.2.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: solodon at mail dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: Configured with: ../configure --prefix=/usr --
                    mandir=/usr/share/
  GCC host triplet: gcc version 3.2.2 20030222
GCC target triplet: Red Hat Linux 3.2.2-5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[solodon at mail dot com]

------- Additional Comments From solodon at mail dot com  2004-10-01 02:19 -------
Created an attachment (id=7250)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7250&action=view)
Preprocessed file


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-01 03:20 -------
Invalid as template operator == (pair<T1,T2>&, pair<T1,T2>&) cannot not match pair<const X, Y> as 
the first operand and pair<X, Y> as the second.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[solodon at mail dot com]

------- Additional Comments From solodon at mail dot com  2004-10-01 03:30 -------
The question here is not about the fact that it doesn't match: I intentionally
made it so that it doesn't match to generate a compilation error, the problem
here is in what is reported in diagnostic message - that is incorrect.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[gdr at cs dot tamu dot edu]

------- Additional Comments From gdr at cs dot tamu dot edu  2004-10-01 03:33 -------
Subject: Re:  Wrong context in error message for template parameter

"pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:

| Invalid as template operator == (pair<T1,T2>&, pair<T1,T2>&) cannot
| not match pair<const X, Y> as the first operand and pair<X, Y> as
| the second. 

I think you're being too hasty in closing this PR. 

And I don't understand your point. 
Could you elaborate?

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-01 03:35 -------
Well that line is correct as it is operator== which cannot be found.
we already fixed the problem:
t.cc:14: error: no match for 'operator==' in 'q. std::_Rb_tree_iterator<_Tp>::operator* [with _Tp = std::
pair<const int, int>]() == p'
for 4.0.0.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[gdr at cs dot tamu dot edu]

------- Additional Comments From gdr at cs dot tamu dot edu  2004-10-01 03:41 -------
Subject: Re:  Wrong context in error message for template parameter

"pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:

| Well that line is correct as it is operator== which cannot be found.

You miss the point of the report.

The issue is not that the operator cannot be found.  The issue is
about the intelligibility of the diagnostic message.

| we already fixed the problem:
| t.cc:14: error: no match for 'operator==' in 'q. std::_Rb_tree_iterator<_Tp>::operator* [with _Tp = std::
| pair<const int, int>]() == p'

This is not what I consider fixing the problem.  I am the one who
specifically put the new error message in 3.4.x (and therefore 4.0.x).
Please reopen this and put it in the category enhancement.'

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-10-01 13:12 -------
Confirmed. Take this smaller testcase: 
---------------------- 
template <typename U> struct Outer { 
    struct Inner {}; 
    Inner foo(); 
}; 
 
typedef int X; 
typedef Outer<X> XOuter; 
 
int main() { 
  Outer<int>  ab; 
  ab.foo() == 1; 
} 
------------------------ 
Clearly, we make no use of the typedefs 'X' and 'XOuter', but we get this 
error message: 
 
g/x> /home/bangerth/bin/gcc-4.0-pre/bin/c++ -c x.cc 
x.cc: In function `int main()': 
x.cc:11: error: no match for 'operator==' in 'ab. Outer<U>::foo [with U = X]() 
== 1' 
 
The part of the error message in brackets should really read '[with U=int]', 
rather than mention 'X'. Note that if I remove the 'XOuter' typedef, then 
I do indeed get what I want. 
 
W. 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-10-01 13:13 -------
. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-10-01 13:13:31
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-10-01 13:15 -------
It is, btw, almost certainly related to PR 99, although there we have 
instantiations rather than typedefs. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[gdr at cs dot tamu dot edu]

------- Additional Comments From gdr at cs dot tamu dot edu  2004-10-01 13:33 -------
Subject: Re:  Wrong context in error message for template parameter

"bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org> writes:

| Confirmed. Take this smaller testcase: 
| ---------------------- 
| template <typename U> struct Outer { 
|     struct Inner {}; 
|     Inner foo(); 
| }; 
|  
| typedef int X; 
| typedef Outer<X> XOuter; 
|  
| int main() { 
|   Outer<int>  ab; 
|   ab.foo() == 1; 
| } 
| ------------------------ 
| Clearly, we make no use of the typedefs 'X' and 'XOuter', but we get this 
| error message: 
|  
| g/x> /home/bangerth/bin/gcc-4.0-pre/bin/c++ -c x.cc 
| x.cc: In function `int main()': 
| x.cc:11: error: no match for 'operator==' in 'ab. Outer<U>::foo [with U = X]() 
| == 1' 
|  
| The part of the error message in brackets should really read '[with U=int]', 
| rather than mention 'X'. Note that if I remove the 'XOuter' typedef, then 
| I do indeed get what I want. 

Thank you, Wolfgang!  The diagnostic is also broken in that it is
printing something nonsensical

   'ab. Outer<U>::foo [with U = X]() == 1'

That isn't C++. 

Please could you assign this to me as enhancement?  
I do not have plan to fix it in time for 4.0.0, though.

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[bangerth at dealii dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gdr at gcc dot gnu dot org
           Severity|normal                      |enhancement
   Target Milestone|4.0.0                       |---


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-10-01 15:57 -------
Done. With respect to the message 
   'ab. Outer<U>::foo [with U = X]() == 1' 
you are right, of course: 
- there shouldn't be any space after "ab." 
- the demangler should probably list the template args after the entire 
  expression, though I suspect that this is going to be a major change... 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] Wrong context in error message for template parameter

[gdr at cs dot tamu dot edu]

------- Additional Comments From gdr at cs dot tamu dot edu  2004-10-01 16:01 -------
Subject: Re:  Wrong context in error message for template parameter

"bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org> writes:

| Done.

Thanks!

| With respect to the message 
|    'ab. Outer<U>::foo [with U = X]() == 1' 
| you are right, of course: 
| - there shouldn't be any space after "ab." 
| - the demangler should probably list the template args after the entire 
|   expression, though I suspect that this is going to be a major change... 

That error is committed in cp/error.c:dump_function_decl().

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] [3.4/4.0/4.1 Regression] Wrong context in error message for template parameter

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-08 22:10 -------
2.95.3 worked correctly:
earth:~>~/ia32_linux_gcc2_95/bin/gcc t.cc
t.cc: In function `int main()':
t.cc:12: no match for `Outer<int>::Inner == int'

This is very much related to PR 23293.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |23293
              nThis|                            |
           Severity|enhancement                 |minor
      Known to work|                            |2.95
            Summary|Wrong context in error      |[3.4/4.0/4.1 Regression]
                   |message for template        |Wrong context in error
                   |parameter                   |message for template
                   |                            |parameter
   Target Milestone|---                         |4.0.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763

[Bug c++/17763] [3.4/4.0/4.1 Regression] Wrong context in error message for template parameter

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.2                       |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17763