bug#5570: automatic cache validation

[Alan Mackenzie]

Hi, Paul,

On Thu, Mar 18, 2010 at 10:05:11PM +0200, Paul Pogonyshev wrote:
> After March the 1st changes indentation in C++ and related modes is
> better, but it still breaks often enough --- to the tune of once every
> 3--5 minutes or so.  Both when editing C++ and Java code.

How about plain C?  Is the breakage connected with templates/generics, as
far as you can see?

What is the breakage like?  Is it a one-off failure which repairs itself
after a few more edits, or is it more like a creeping death?  Does
reinitializing the mode (M-x c++-mode) repair the indentation?  Does
saving the file and reloading it fix things?

Does
    M-x (c-state-cache-init)
fix it?

> As I understand, the issue is that some cached information becomes
> wrong after certain (undetermined) buffer changes.

This is very likely.

> Maybe it is better to write an automated cache validation code rather
> than search for a certain way to reproduce stuff?

For which cache, though?  Hence the questions above.  

> E.g. just build information from scratch and assert that cached
> information is the same.  Ideally, such checks should be performed
> after every change, so that you'd be able to find which change exactly
> trigerred a bug.  (Granted, this would make debugging version slow as
> hell, but with this rate of error occurence it's not like you'd need
> to run it for days.)

I should be able to get this done by, say, Monday for the "state-cache".
Again, does M-x (c-state-cache-init) clear the fault?

> Without automated error detection tools cc-mode is bound to have
> similar issues after every second non-trivial change.

I strongly believe it's a very small finite number of distinct bugs
causing the problems.  Anything more you can tell me about how it breaks
would be of the utmost help.

> Paul

-- 
Alan Mackenzie (Nuremberg, Germany).