bug#29959: cc-mode: wrong indentation in absence of semicolon

[Alan Mackenzie <acm@muc.de>]

Hello, Konstantin.

On Sat, Jan 13, 2018 at 14:11:31 +0300, Konstantin Kharlamov wrote:
> Just tested with current git, the problem is still present.

> I am almost sure this is a regression, I don't remember having that 
> problem before. The real-world consequences are just too annoying for it 
> to go unnoticed — basically, every time I'm typing variables indentation 
> just doesn't work. And I also seem to remember a few irrelevant 
> situations where I was typing conditions with the like results.

The problem originates in a new feature, C99 compound literals, which was
committed on 2017-11-10.  This detects brace blocks (meaning something
like the initialisation of a struct) in the middle of executable code,
but it is clear the test for such a brace block isn't rigorous enough,
since even function blocks are being mistaken for them.

> On 03.01.2018 09:02, Konstantin Kharlamov wrote:
> > # Steps to reproduce:
> > 1. Open emacs -Q test.c
> > 2. Write the following:

> > int main() {
> >      int a,
> > }

> > 3. put the caret after the comma symbol, and press enter, e.g. to
> > continue writing variables on the new line.

> > # Expected:
> > the new line alignment stands out with regard to the prev. line.

> > # Actual:
> > the new line aligned to the beginning of the prev. line.

> > # Workarounds:
> > Typing the following text:

> > int main() {
> >      int a,;
> > }

> > …then pressing enter right after the comma works as expected.

At the moment, the bug you're seeing is triggered by CC Mode checking for
commas and semicolons in blocks; if the last such delimiter is a comma,
the block is taken as a brace block.  So a workaround, for the moment, is
to ensure that you have a semicolon in each block as the last delimiter
there.

I will be working on fixing this bug.  Thanks for taking the trouble to
report it.

> > ------------

> > In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.26)
> >   of 2017-12-15 built on constantine-N61Ja
> > Repository revision: 6c301afa70f6eac32ad1ce92412ea3cf6fcdeeca
> > Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
> > System Description: Arch Linux

[ .... ]

-- 
Alan Mackenzie (Nuremberg, Germany).