[RFC] Patch to fix Infinite Stack Recursion Regression

[Fariborz Jahanian <fjahanian at apple dot com>]

Attached test case causes infinite stack recursion with gcc mainline.  
It is cause by fix to PR17413. Test should issue a diagnostic instead.

Before the patch:
% mygccm5plus -c local6.C
Out of stack space.
Try running 'limit stacksize unlimited' in the shell to raise its limit.

With the patch:
% mygcctplus !*
mygcctplus -c local6.C
local6.C: In member function 'PCVector2<T> PCVector2<T>::operator- 
(const PCVector2<T>&) const [with T = double]':
local6.C:18:   instantiated from here
local6.C:7: error: no matching function for call to  
'PCVector2<double>::PCVector2(const double&, const double&)'
local6.C:2: note: candidates are: PCVector2<double>::PCVector2(const  
PCVector2<double>&)


Attached patch (against apple's local branch) fixes it. If it looks  
reasonable, I will provide an FSF patch. This patch has been  
bootstrapped and dejagnu++ tested on apple-ppc-branch.
Bug introduced when gcc-4.0 started doing template deduction on  
arguments which do not depend on template argument. Call to  
can_convert_arg is made for this purpose. Part of type checking  
involves call to implicit_conversion which then calls  
build_user_type_conversion_1 to find a candidate for type conversion.  
But to find such a convesion, look up must be only looking for non- 
converting constructors. This is accomplished by passing  
LOOKUP_ONLYCONVERTING flag to build_user_type_conversion_1. Bug is  
that this flag gets  passed down all the way to  
add_template_candidate_real, but not further. Fix is to pass this  
flag further down to fn_type_unification and to
type_unification_real, called by fn_type_unification, so next search  
for doing non-template dependent argument deduction is done in this  
lookup mode.

- fariborz (fjahanian@apple.com)


cp/ChangeLog:

2005-07-25 Fariborz Jahanian <fjahanian@apple.com>

        * cp-tree.h (can_convert_arg, fn_type_unification): New  
argument.
        * call.c (add_template_candidate_real): Pass down 'flags' to
        fn_type_unification.
        (can_convert_arg): New 'flags' argument. Pass it to call to
        implicit_conversion instead of LOOKUP_NORMAL.
        * class.c (resolve_address_of_overloaded_function): Add
        LOOKUP_NORMAL in call to can_convert_arg.
        (resolve_address_of_overloaded_function): Ditto.
        * decl.c (reshape_init, check_default_argument): Ditto.
        * typeck.c (build_ptrmemfunc): Ditto.
        * typeck2.c (digest_init): Ditto.
        (unify): Add LOOKUP_NORMAL to call to type_unification_real.
        * pt.c (type_unification_real): Add 'flags' argument.
        (fn_type_unification): Pass 'flags' to type_unification_real.
        (type_unification_real): Pass new 'flags' argument to call to
        can_convert_arg.

Attachment: radar-patch-4187916.txt
Description: Text document

Attachment: local6.C
Description: Binary data