[cfe-dev] Default arguments considered harmful?

[Philip Reames]

On 05/02/2014 02:18 AM, David Chisnall wrote:
> On 2 May 2014, at 09:16, David Tweed <david.tweed at arm.com> wrote:
>
>> I wonder if, with C++11 named initialization syntax for PODs, something
>> could be done so that in cases like this a (function specific, I guess)
>> "optional options object" could be used. (This would avoid one of the big
>> problems with C++ optional arguments, which is that if one towards the end
>> needs to be set to a non-default value all the preceding options need
>> setting.) That would certainly make things a lot easier to read in cases
>> like these.
> The related issue is that they complicate overloading.  I've been bitten a few times in clang code by the compiler deciding that, when I specified a pointer instead of a reference for a parameter, it would happily coerce it to a bool and then use the default values for the rest of the parameters, giving some very strange results - no errors, no warnings, just the code doing something unexpected.
>
> David
>
David, I think you're pointing out a slightly different issue... one 
I've also been bitten by.

Does anyone know of a legitimate reason to have an implicit conversion 
to bool as a function argument?  Maybe we should add an optional warning 
for this case in particular?

Philip