On 9/30/21 4:33 PM, Andrey Semashev wrote:

On 9/30/21 1:12 PM, rajesh daggumati via Boost wrote:

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Hi Team, PFB code snippet: try { BOOST_THROW_EXCEPTION(std::invalid_argument("Blah")); } catch(...) { boost::exception_ptr exception = boost::current_exception(); const std::invalid_arguement* p; try{ boost :: rethrow_exception(exceptionptr) } catch(std::invalid_argument &e) { p = dynamic_cast(&e) } const std::invalid_argument* actualStdPtr = ExceptionHelper::ExtractConstPtrstd::invalid_argument(exceptionptr); EXPECT_TRUE(((void*)p) == ((void*)actualStdPtr)) << "Same Object"; //this condition is getting failed. }} static const t* ExtractConstPtr(boost::exception_ptr ep) { try { boost::rethrow_excepton(ep); } catch(T &e){ const T* exceptType = dynamic_cast(&e); return exceptType; } catch (std::exception & e){ const T* exceptType = dynamic_cast(&e); return exceptType; } } //EXPECT_TRUE(((void*)p) == ((void*)actualStdPtr)) -->what will be the reason to get failed as I do same thing in both cases.

Throwing an exception (which is part of rethrow_excepton) creates a copy of the exception (http://eel.is/c++draft/except.throw#3). So the object referred to by exception_ptr and the object you receive in the catch block are different objects. Same with different catch blocks - every time you catch an exception, you catch a new object.

To be more accurate - every time you throw an exception, you catch a new object. Which is what happens in your example.

Also, the pointer to the caught exception (i.e. the one you receive in the catch block) is dangling as soon as you leave the catch block, as the exception is destroyed at this point. It may compare equal between different catch blocks by accident, but in general it is invalid to use it like you do.