On 11/13/14 10:33 AM, Aaron Ballman wrote:
On Wed, Nov 12, 2014 at 5:05 PM, Richard Smith <[email protected]> wrote:
I think it's not too hard to avoid the quadratic performance here. Algorithm
outline:
Start with empty map of type -> handlers
For each catch handler for a type T:
For each base class U of T (including T itself), most-derived-first:
If we have a handler for U in our map, warn, break
Add handler for T to our map
(This is still quadratic if you have struct A<n> : A<n-1>, and catch A<0>,
A<1>, ..., A<n> in that order, but in that case I think your approach is
cubic (because IsDerivedFrom is itself linear in the number of base
classes.)
I've reworked the patch to implement your algorithm. Thanks!
Also, I'm not sure you're correctly handling this case:
try { ... }
catch (Base *) {}
catch (Derived &) {}
We shouldn't warn here, but I think you might, because you strip off a
top-level * or & quite early. I'd also like to see some test coverage for
catch parameters with cv-qualifiers.
Aaron,
I remember adding some tests to libcxxabi which exhaustively check a few of the
cv-requirements for catch handlers... maybe those are a useful starting point
for this? Those tests are in libcxxabi/test/catch_pointer_reference.cpp
Cheers,
Jon
Correct, that was handled incorrectly before, but has been fixed in
this patch. I've added some further tests to make sure of it.
Thanks!
~Aaron
--
Jon Roelofs
[email protected]
CodeSourcery / Mentor Embedded
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