Does anyone still feel strongly about -Wdeclaration-after-statement ?

[Peter Hutterer]

On Sun, Jul 28, 2024 at 05:48:45PM -0700, Alan Coopersmith wrote:
> Back when we first added a default set of compiler warning flags to our
> xorg-macros.m4 for autoconf in 2008, we included -Wdeclaration-after-statement
> since not all the compilers at the time supported this C99 feature (most
> notably some OpenBSD ports that used gcc 2.95, but also MSVC versions before
> 2013).
> 
> Since then we've widely adopted other C99 features such as struct initializers
> and declaring variables in for loops ("for (int i = 0; ....)"), but last
> time we discussed this warning in 2013, decided to leave it in place as
> a style choice, not a technical constraint - see the thread starting at:
> https://lists.freedesktop.org/archives/xorg-devel/2013-September/037735.html
> 
> But we didn't carry that flag over in our meson conversions - apparently
> intentionally so in the case of the X server code base:
> https://gitlab.freedesktop.org/xorg/xserver/-/commit/db465bae533f85e7f900deb96efecc831c9d550b
> so people patching the X server don't get told that we don't like that style,
> and so now Enrico has submitted a number of merge requests that use it to
> simplify some of our previous code, such as:
> https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1601
> 
> Do we want to keep insisting on this as part of our style, or have people
> gotten used to it from other languages/projects now and are willing to
> accept it in X.Org code?
> 
> Is it time to re-apply
> https://gitlab.freedesktop.org/xorg/util/macros/-/commit/689ea0ec5d8b7594ba2fa9e27b2458cea8a58724
> to util-macros?

I feel fairly strongly about removing that warning, i.e. allowing
declarations after statements. There's a reason all modern languages
allow this. It makes the code clearer and less buggy in many instances,
esp. in regards to variables that don't need to exist until various
checks have been performed. And it allows those variables to be
initialized immediately, so one source of bugs less. Doubly so with
__attribute__((cleanup)) but that's a conversation for another day...

Having said that, sticking with the local code style still trumps
anything, if you have 6 temp variables declared at the top mixed with 5
declared later that's more confusing than if all were at the top.

Cheers,
  Peter