Re: [PATCH] Objective-C: fix protocol list count type (pertinent to non-LP64)

[Matt Jacobson <mhjacobson@me.com>]

> On Oct 25, 2021, at 5:43 AM, Iain Sandoe <iain@sandoe.co.uk> wrote:
> 
> Did you test objective-c++ on Darwin?
> 
> I see a lot of fails of the form:
> Excess errors:
> <built-in>: error: initialization of a flexible array member [-Wpedantic]

Looked into this.  It’s happening because obj-c++.dg/dg.exp has:

    set DEFAULT_OBJCXXFLAGS " -ansi -pedantic-errors -Wno-long-long"

Specifically, the `-pedantic-errors` argument prohibits initialization of a 
flexible array member.  Notably, this flag does *not* appear in objc/dg.exp.

Admittedly I didn’t know that initialization of a FAM was prohibited by the 
standard.  It’s allowed by GCC, though, as documented here:

<https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html>

Is it OK to use a GCC extension this way in the Objective-C frontend?

> For a patch that changes code-gen we should have a test that it produces what’s
> expected (in general, a ‘torture' test would be preferrable so that we can be sure the
> output is as expected for different optimisation levels). 

The output is different only for targets where 
sizeof (long) != sizeof (void *).  Do we have the ability to run “cross” 
torture tests?  Could such a test verify the emitted assembly (like LLVM’s 
FileCheck tests do)?  Or would it need to execute something?

Thanks for your help!

Matt