Re: MFC Exception TRY/CATCH without the braces { } can compile
On Thu, 21 Jun 2007 11:00:29 GMT, MrAsm <mrasm@usa.com> wrote:
http://members.cox.net/doug_web/eh.htm#Q6
Hi Doug,
in your MfcGenericException code you have the protected ctor which
takes a 'const char *':
explicit MfcGenericException(const char* pMsg)
: m_msg(pMsg)
My understanding is that you choose to use 'const char *' because you
need to initialize using std::exception::what (which returns a 'const
char*').
Am I correct?
Yep.
But would that compile only in ANSI builds?
Nope.
Or has the CString class (m_msg is a CString instance in your code)
also a constructor for conversion from ANSI to Unicode (const char *
--> const wchar_t *) in Unicode builds?
Yep. (The original version used a char array. I switched to CString to
simplify the code and decrease the size of MfcGenericException objects
while still being able to record long messages.)
Or does it exist a Unicode version of std::exception (e.g.
std::wexception)?
Nope.
Or does std::exception use UTF-8?
Nope.
Moreover: if a memory exception is thrown, is the system ready to
create new classes, calling constructors, etc...?
The "memory" in "memory exceptions" is heap memory, and MFC does something
smart with CMemoryException. It throws a pointer to a static object and so
avoids using the heap. This is why you must use CException::Delete instead
of the delete keyword; the former can be overridden to distinguish between
objects on the heap and those not. Given how uncommon it is for a memory
exception to occur, the risk of the original exception being replaced by a
memory exception is tiny. Moreover, I don't know of anything that would
allow an exception implementation to enter a state where it can't throw
exceptions. AFAIK, in an implementation than can run out of resources such
as heap and become unable to throw the requested exception, there has to be
some fail-safe exception that it can throw. (I'm not counting things
outside the language, such as stack overflow.)
Or are memory exceptions a very *uncommon* condition?
Exceedingly uncommon on a virtual memory system. ISTR Andrew Koenig
remarking that before a user-level program on a VM system starts throwing
memory exceptions, the user will have terminated it because it will have
brought the system to its knees due to pagefile thrashing. He has a point.
--
Doug Harrison
Visual C++ MVP