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Attempt to solve issue #10 (#24)

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* Attempt to solve issue #10

In boost::current_exception(), after all supported types of exception have
been checked for, a boost::unknown_exception is stored in the
boost::exception_ptr as a last resort to signal that an exception was indeed
stored, but that the actual type and value of the exception was lost.

Now, in case C++11 std::current_exception() is supported, the
std::exception_ptr result of calling std::current_exception() is what
gets stored inside the boost::exception_ptr. Later, inside
boost::rethrow_exception, the std::exception_ptr is retrieved from
the boost::exception_ptr and whatever exception it stores is thrown via
std::rethrow_exception().

The main benefit is than now any exception thrown via plain 'throw'
can be trasnported via boost::exception_ptr. Before this change it was
required that the throw site either used boost::enable_current_exception()
or boost::throw_exception() or threw an exception type inheriting from
boost::exception, which was impossible for third party software
that does not use Boost.Exception.

The detection of std::current_exception() is currently done via config macro
BOOST_NO_CXX11_NOEXCEPT, assuming that if 'noexcept' is supported then
std::exception_ptr is also supported. A better solution would require a new
dedicated macro in Boost.Config.

* Detect support for std::current_exception() via config macro BOOST_NO_CXX11_HDR_EXCEPTION

The temporary solution via BOOST_NO_CXX11_NOEXCEPT was an ugly hack
that is no longer necessary now that Boost.Config has
BOOST_NO_CXX11_HDR_EXCEPTION (pending merge to develop).

* Attempt to solve issue #10

In boost::current_exception(), after all supported types of exception have
been checked for, a boost::unknown_exception is stored in the
boost::exception_ptr as a last resort to signal that an exception was indeed
stored, but that the actual type and value of the exception was lost.

Now, in case C++11 std::current_exception() is supported, the
std::exception_ptr result of calling std::current_exception() is what
gets stored inside the boost::exception_ptr. Later, inside
boost::rethrow_exception, the std::exception_ptr is retrieved from
the boost::exception_ptr and whatever exception it stores is thrown via
std::rethrow_exception().

The main benefit is than now any exception thrown via plain 'throw'
can be trasnported via boost::exception_ptr. Before this change it was
required that the throw site either used boost::enable_current_exception()
or boost::throw_exception() or threw an exception type inheriting from
boost::exception, which was impossible for third party software
that does not use Boost.Exception.

The detection of std::current_exception() is currently done via config macro
BOOST_NO_CXX11_NOEXCEPT, assuming that if 'noexcept' is supported then
std::exception_ptr is also supported. A better solution would require a new
dedicated macro in Boost.Config.

* Detect support for std::current_exception() via config macro BOOST_NO_CXX11_HDR_EXCEPTION

The temporary solution via BOOST_NO_CXX11_NOEXCEPT was an ugly hack
that is no longer necessary now that Boost.Config has
BOOST_NO_CXX11_HDR_EXCEPTION (pending merge to develop).

* Document detection of C++11 std::current_exception through BOOST_NO_CXX11_HDR_EXCEPTION

* Added dist: trusty for Travis config, as recommended by pdimov in issue #10

* Stupid gcc 4.7 and 4.8 are confused initializing a reference with braces, using equal sign hoping it works (tested similar code on godbolt).
This commit is contained in:
dmenendez-gruposantander
2020-01-29 22:41:48 +01:00
committed by GitHub
parent f68cd7b2d4
commit af98afb3d1
3 changed files with 161 additions and 1 deletions
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129
test/unknown_exception_test.cpp
View File

@ -38,6 +38,25 @@ throw_unknown_exception()
throw test_exception();
}
struct
user_defined_exception
{
user_defined_exception(int d):data(d){}
int data;
};
void
throw_user_defined_exception()
{
throw user_defined_exception(42);
}
void
throw_builtin_exception()
{
throw 42;
}
int
main()
{
@ -138,5 +157,115 @@ main()
BOOST_TEST(false);
}
}
try
{
throw_user_defined_exception();
}
catch(
... )
{
boost::exception_ptr ep=boost::current_exception();
try
{
rethrow_exception(ep);
}
#ifndef BOOST_NO_CXX11_HDR_EXCEPTION
catch(
user_defined_exception & x)
{
//Yay! std::current_exception to the rescue!
BOOST_TEST( 42==x.data );
}
#else
catch(
boost::unknown_exception & )
{
//Boo! user defined exception was transported as a boost::unknown_exception
}
#endif
catch(
... )
{
BOOST_TEST(false);
}
try
{
rethrow_exception(ep);
}
#ifndef BOOST_NO_CXX11_HDR_EXCEPTION
catch(
user_defined_exception & x)
{
//Yay! std::current_exception to the rescue!
BOOST_TEST( 42==x.data );
}
#else
catch(
boost::unknown_exception & )
{
//Boo! user defined exception was transported as a boost::unknown_exception
}
#endif
catch(
... )
{
BOOST_TEST(false);
}
}
try
{
throw_builtin_exception();
}
catch(
... )
{
boost::exception_ptr ep=boost::current_exception();
try
{
rethrow_exception(ep);
}
#ifndef BOOST_NO_CXX11_HDR_EXCEPTION
catch(
int & x)
{
//Yay! std::current_exception to the rescue!
BOOST_TEST( 42==x );
}
#else
catch(
boost::unknown_exception & )
{
//Boo! builtin exception was transported as a boost::unknown_exception
}
#endif
catch(
... )
{
BOOST_TEST(false);
}
try
{
rethrow_exception(ep);
}
#ifndef BOOST_NO_CXX11_HDR_EXCEPTION
catch(
int & x)
{
//Yay! std::current_exception to the rescue!
BOOST_TEST( 42==x );
}
#else
catch(
boost::unknown_exception & )
{
//Boo! builtin exception was transported as a boost::unknown_exception
}
#endif
catch(
... )
{
BOOST_TEST(false);
}
}
return boost::report_errors();
}