Re: C++0x/1x exception specifications proposal: Compile-time checked

From:

Ioannis Vranos <ivranos@no.spamfreemail.nospam.gr>

Newsgroups:

comp.lang.c++

Date:

Tue, 22 Jan 2008 14:15:27 +0200

Message-ID:

<fn4mp0$p7v$1@ulysses.noc.ntua.gr>

Ioannis Vranos wrote:

The solution that I propose on this, is the keyword :exceptions or
:_exceptions:

void somefunc2() _throw(graph_exception)
{
  throw graph_exception();
}

void somefunc1() _throw(time_exception)
{

  somefunc2();

  throw time_exception();

} _nothrow(std::out_of_range)

int main()
{
  somefunc1() :exceptions;
}

at compile-time it will produce a compiler message, something like:

"main()::somefunc1() may throw exceptions:
somefunc1()::somefunc2()::graph_exception, somefunc1::time_exception".

After we write our exception handlers, we can remove the keyword
":exceptions" from somefunc1(); statement in main(), and thus main becomes:

void somefunc2() _throw(graph_exception)
{
  throw graph_exception();
}

void somefunc1() _throw(time_exception)
{

  somefunc2();

  throw time_exception();

} _nothrow(std::out_of_range)

int main() try
{
  somefunc1();
}

catch(graph_exception)
{
  // ...
}

catch(time_exception)
{
// ...
}

Compiler checks/errors:

Where the source code is available to the compiler, any
_nothrow(some_exception) specification at a function/member function,
must have at least one equivalent catch(some_exception) or catch(...)
exception handler at the function definition.

For example:

void somefunc() _throw()
{
   int *p= new int[10];

} _nothrow (std::bad_alloc)

should be flagged as a compiler error, because there is no
catch(std::bad_alloc) or catch(...) exception handler at the function
definition.

The following should be correct:

1 .

void somefunc() try _throw()
{
   int *p= new int[10]

} _nothrow (std::bad_alloc)

catch(std::bad_alloc)
{
  // ...
}

2.

void somefunc() try _throw()
{
   int *p= new int[10]

} _nothrow (std::bad_alloc)

catch(...)
{
   // ...
}

3.

void somefunc() try _throw()
{
   int *p= new int[10]

} _nothrow (...)

catch(...)
{
   // ...
}