On Sat, Feb 01, 2020 at 04:57:26PM +0100, Ingo Schwarze wrote: > Hi Jeremie, > > Jeremie Courreges-Anglas wrote on Sat, Feb 01, 2020 at 01:37:32PM +0100: > > On Fri, Jan 31 2020, Ingo Schwarze <schwa...@usta.de> wrote: > >> ngc...@gmail.com wrote on Fri, Jan 31, 2020 at 10:14:52PM +0900: > > >>> Reduce scope of a few variables. > > >> No, this contradicts OpenBSD coding style. > >> We want local variables declared up front in functions > >> such that you can see at one glance which variables exist. > > > Huh, this is your personal preference and I strongly disagree with > > making it an "official" stance (again). Reducing the scope of variables > > *quite often* helps reasoning about them. > > > > style(9) said something like that, and has been changed three years > > ago (for good IMO). > > > > revision 1.68 > > date: 2016/10/18 18:13:56; author: millert; state: Exp; lines: +2 -4; > > commitid: aPPHgmmA4hseZUFx; > > Don't tell the programmer not to put variable declarations inside > > blocks. OK guenther@ kettenis@ > > Oops. Sorry for forgetting that the recommendation was dropped and > for making you dig up the commit and thanks for reminding me.
Since it came out in the open, I also like declaring variables as late as possible. Specifically, because the old-style (declare variables early, then give them a value when possible) tends to be unsafe. You forget about initializing variables, or you initialize them to something that doesn't make sense. I also don't think it's more readable to have every variable at the start of the function. The less space my eyes have to travel the better. Especially with functions that run 50 lines long. Also, reducing the scope of variables tends to be one of the first steps in untangling old atrocious code: reduce scope, figure out you got two separate blocks in your function with totally separate variables, and then you write a new function. Compilers aren't perfect yet, but we still deal with code that was written 20-30 years ago, back when they were even worse, and a lot of dirty tricks that were used back then are no longer needed. Reusing variables, having the compiler match your scopes in asm exactly, you name it. These days, scope is only a semantic promise that this variable only matters in THAT specific block of code. The stronger the promise, the more readable the code.
