[mythtv] [mythtv-commits] [MythTV/mythtv] 704f5e: android: Fix problem with frontend setup

[Peter Bennett]

On 1/27/20 11:04 AM, David Hampton wrote:
> On Mon, 2020-01-27 at 09:00 -0500, Peter Bennett wrote:
>>
>> On 1/27/20 1:47 AM, Klaas de Waal wrote:
>>> On Mon, 27 Jan 2020 at 01:31, Peter Bennett <noreply at github.com>
>>> wrote:
>>>>    Branch: refs/heads/master
>>>>    Home:   https://github.com/MythTV/mythtv
>>>>    Commit: 704f5ef3660792b80709d17ebe24724326de3b4a
>>>>        
>>>> https://github.com/MythTV/mythtv/commit/704f5ef3660792b80709d17ebe24724326de3b4a
>>>>    Author: Peter Bennett <pbennett at mythtv.org>
>>>>    Date:   2020-01-26 (Sun, 26 Jan 2020)
>>>>
>>>>    Changed paths:
>>>>      M mythtv/libs/libmyth/standardsettings.cpp
>>>>      M mythtv/libs/libmythui/mythdialogbox.cpp
>>>>
>>>>    Log Message:
>>>>    -----------
>>>>    android: Fix problem with frontend setup
>>>>
>>>> using auto for a dynamic cast was not working. Changed to
>>>> appropriate object type.
>>>>
>>>>
>>> Can this be an issue in more places in the code?
>>>
>>> Klaas.
>>>
>>>
>>   Hi Klaas
>>
>> I think it could be. This came up with Mark Spieth's packaging change
>> to  use a new compiler. I will look through the code to see if there
>> are many uses of "auto" and whether they are working on android.
> Hi Peter,
>
> I noticed that your commit also included a change from dynamic_cast to
> static_cast.  Those are very different animals, and that's far more
> likely the cause of the problem.  The former happens at runtime and can
> fail and return nullptr; the latter happens at compile time.  Could
> that fix be what made the code work again, not the auto changes?

Oops - mistake - I tried static_cast and then changed it back to 
dynamic_cast (at least I thought I did). Something slipped through the 
cracks. I will revisit that.  Note in this case static cast should not 
cause a failure since the line above checks the type. However I will try 
dynamic_cast again and see if I can sort that out correctly.
>>   I am not very familiar with "auto" and its usage, but in this case
>> it seemed unnecessary because you could see the type right there in
>> the code.
> One of the reasons to use auto is that you don't have to repeat the
> same type name in a single line of code.  :-)  I know for simple short
> time names its just as easy to write the type twice, bit for long
> complicated names its easier to write "auto".


>>   Other places where they assign auto to the result of a complicated
>> expression may be more difficult to fix if they are not working. What
>> was particularly confusing was that the code seemed to use "auto" and
>> "auto *" interchangeably when creating a pointer.
> Yes, that's a little confusing.  If you use the "auto" keyword by
> itself, it does figure out that that right side of the equals sign is a
> pointer and will correctly use a pointer.  "Auto *" deduces the exact
> same type, but it reads easier to us humans.  There's newer code in
> clang-11 to ensure that it replaces duplicated type declarations with
> "auto", "auto *", "auto &", or "const auto *" where appropriate.  All
> essentially work out the same to the compiler, but the latter three are
> more readable to humans.  I have a fix in my working branch that
> updates a number of instance of "auto" to be "auto *".  I was waiting
> until after the v31 split to merge the changes, but I can cherry-pick
> that fix into master if the group wants.
>
>>   This was working in linux and the old compiler but not the new
>> compiler.
> Sound like I need to update my setup for the new compiler and sdk/ndk.
>
> David
>
>
>
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