CODEWITHSUNDEEP
c++try-catch
Echren
Echren

Reputation: 61

About C++ vector::push_back() exceptions. Ellipsis catch useful?

I often write code like this :

try
{
    vec.push_back(0);
}
catch(const std::bad_alloc &)
{
    ec=1;
}
catch(...)
{
    ec=2;
}

Is the ellipsis catch useful? Can you provide some links where I can find everything I need to know about exceptions thrown by cin, vector, ifstream, etc? All C++ things... Something like The Open Group Base Specifications Issue 7 (http://pubs.opengroup.org/onlinepubs/9699919799/) where you can find functions names, parameters, return values, flags, errno codes, etc.

Upvotes: 1

Views: 7055

Answers (2)

Dietmar Kühl
Dietmar Kühl

Reputation: 153955

I haven't seen any restrictions on what exceptions can be thrown but there is footnote 192 which contains this statement:

... Library implementations should report errors by throwing exceptions of or derived from the standard exception classes(18.6.2.1 ,18.8, 19.2).

This a footnote on 17.6.5.12 [res.on.exception.handling] paragraph 4 which also contains this sentence:

... Any other functions defined in the C++ standard library that do not have an exception-specification may throw implementation defined exceptions unless otherwise specified.

It seems, any decent implementation would throw only exceptions derived [indirectly] from std::exception. That is, I would catch std::exception const& and probably report the what() string povided by this exception in some form (e.g., log it to a suitable destination).

Upvotes: 2

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

If an ellipsis catch is really useful is arguable IMHO. You should at least catch a std::exception for matching the broader case

try {
    vec.push_back(0);
}
catch(const std::bad_alloc &) {
    ec=1;
}
catch(const std::exception &) {
    ec=2;
    // You can inspect what() for a particular reason, or even try to dynamic_cast<>
    // to find out which specific exception was thrown.
}
catch(...) {
    // You have no more type info here, this should be done for last resort (in the
    // outermost scope) only.
    ec=3;
}

I left comments about the advantages/disadvantages

Upvotes: 3

Related Questions