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From: bangerth@dealii.org To: gcc-gnats@gcc.gnu.org Subject: c++/10864: [diagnostic] Unreadable error message for "no match for 'A < B' operator" if A,B are templates Date: Mon, 19 May 2003 15:16:00 -0000 [thread overview] Message-ID: <20030519151237.6498.qmail@sources.redhat.com> (raw) >Number: 10864 >Category: c++ >Synopsis: [diagnostic] Unreadable error message for "no match for 'A < B' operator" if A,B are templates >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: sw-bug >Submitter-Id: net >Arrival-Date: Mon May 19 15:16:00 UTC 2003 >Closed-Date: >Last-Modified: >Originator: Wolfgang Bangerth >Release: unknown-1.0 >Organization: >Environment: present mainline >Description: This startled me, since I didn't see exactly what gcc was complaining about -- I had code like ------------------------------ #include <string> #include <vector> template <class T> struct less { bool foo () { return T() < T(); } }; template <typename,typename> class X {}; template struct less<X<std::vector<std::string>, std::vector<std::string> > >; ----------------------- (In fact it was even a little more complicated...). gcc gives the following message (on mainline): g/x> /home/bangerth/bin/gcc-3.4-pre/bin/c++ -c y.cc y.cc: In member function `bool less<T>::foo() [with T = X<std::vector<std::string, std::allocator<std::string> >, std::vector<std::string, std::allocator<std::string> > >]': y.cc:10: instantiated from here y.cc:5: error: no match for `X<std::vector<std::string, std::allocator<std::string> >, std::vector<std::string, std::allocator<std::string> > > < X<std::vector<std::string, std::allocator<std::string> >, std::vector<std::string, std::allocator<std::string> > >' operator Now, that's pretty hard to read. What it says is: no match for `A < B' operator but the "<" is totally lost in all these template args. I also always thought that the message was somehow truncated, since usually in C++ there must be something after the "operator" :-) I think it would be nice if the message could be changed to read like no match for operator< in expression `A < B' That way it would be simpler to figure out which operator exactly is missing. W. PS: As a heads up: this is what 2.95 produces on above code, which is way worse since it even states the template args of the typedef expansion of std::string... g/x> c++ -c y.cc y.cc: In method `bool less<X<vector<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> >,allocator<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> > > >,vector<basic_string<char,string_char_traits<char >How-To-Repeat: >Fix: >Release-Note: >Audit-Trail: >Unformatted: >,__default_alloc_template<true,0> >,allocator<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> > > > > >::foo()': y.cc:10: instantiated from here y.cc:5: no match for `X<vector<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> >,allocator<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> > > >,vector<basic_string<char,string_char_traits<char>,__d efault_alloc_template<true,0> >,allocator<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> > > > > < X<vector<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> >,allocator<basic_string<char,string_char _traits<char>,__default_alloc_template<true,0> > > >,vector<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> >,allocator<basic_string<char,string_char_traits<char>,__default_alloc_template<true,0> > > > >'
next reply other threads:[~2003-05-19 15:16 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-05-19 15:16 bangerth [this message] 2003-05-19 21:17 Gabriel Dos Reis 2003-05-20 0:39 bangerth 2003-05-20 3:16 Giovanni Bajo
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