[Bug c++/49027] New: g++ ignores -fno-exceptions in uninstantiated template

[Bug c++/49027] New: g++ ignores -fno-exceptions in uninstantiated template

[ian at airs dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49027

           Summary: g++ ignores -fno-exceptions in uninstantiated template
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ian@airs.com


This file compiles without error when using -fno-exceptions:

extern int f2();
template<typename T>
void f1() {
  try { f2(); } catch (...) { }
}

Compiling this very similar file:

extern int f2();
template<typename T>
void f1() {
  try { f2(); } catch (...) { }
}
template f1<int>();

gives these errors:

foo.cc: In function ‘void f1() [with T = int]’:
foo.cc:6:   instantiated from here
foo.cc:4: error: exception handling disabled, use -fexceptions to enable

I think it would be more consistent for g++ to reject uses of try/catch when
compiling with -fno-exceptions even in uninstantiated templates.  Otherwise you
can get surprising results when code changes: you can find problems in very
different pieces of code.

[Bug c++/49027] g++ ignores -fno-exceptions in uninstantiated template

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49027

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-05-18 09:43:37 UTC ---
I'm not sure.  What about

extern int f2();
struct NoExcept {};
template<typename T>
void f1() {
  try { f2(); } catch (...) { }
}
template<>
void f1<NoExcept>() {
  f2();
}
template f1<NoExcept>();

?  EH code could be disabled by some tags and specialization.  Especially
for a library that has a non-exception variant that would sound useful.

[Bug c++/49027] g++ ignores -fno-exceptions in uninstantiated template

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49027

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-18 17:36:18 UTC ---
IIRC this was done on purpose but I cannot find the original discussion.