The description of uncaught_exception() throw() function states (18.6.4):
Returns: true after completing evaluation of a throw-expression until either
completing initialization of the exception-declaration in the matching handler
or entering unexpected() due to the throw; or after entering terminate() for
any reason other than an explicit call to terminate().
Apart from an explicit call to terminate() from the user's code, terminate() is
called in the following situations (15.5.1):
1. When the exception handling mechanism, after completing evaluation of the
expression to be thrown but before the exception is caught, calls a user
function that exits via an uncaught exception.
2. When the exception handling mechanism cannot find a handler for a thrown
exception.
3. When the destruction of an object during stack unwinding exits using an
exception.
4. When construction or destruction of a non-local object with static storage
duration exits using an exception.
5. When execution of a function registered with atexit exits using an
exception.
6. When a throw-expression with no operand attempts to rethrow an exception and
no exception is being handled.
7. When unexpected throws an exception which is not allowed by the previously
violated exception specification, and std::bad_exception is not included in
that exception-specification.
However std::uncaught_exception called within a terminate_handler returns false
in the cases 2,4,5,7 and true in the other cases (terminate_handler is
specified using std::set_terminate()).
The attached examples demonstrate the above 7 situations when terminate() is
called "implicitly" and display the return value of std::uncaught_exception().
For example, reproducing situation 2:
[EMAIL PROTECTED]:/mnt/hgfs/shared/temp/test$ g++ -Wall test2.cpp && ./a.out
Exception will be thrown and it won't be catched.
This situation meets the following condition when terminate should be called:
2.When the exception handling mechanism cannot find a handler
for a thrown exception.
Inside terminate_handler uncaught_exception() returns *false*.
terminate called after throwing an instance of 'char const*'
Aborted (core dumped)
[EMAIL PROTECTED]:/mnt/hgfs/shared/temp/test$ g++ --version
g++ (GCC) 4.1.2 (Ubuntu 4.1.2-0ubuntu4)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
--
Summary: std::uncaught_exception() returns wrong value after
entering terminate() in some cases
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tsyvarev at ispras dot ru
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37477
