Re: [patch] Enable lightweight checks with _GLIBCXX_ASSERTIONS.

[Jonathan Wakely <jwakely at redhat dot com>]

On 09/09/15 14:54 +0100, Jonathan Wakely wrote:
> On 08/09/15 21:52 +0200, François Dumont wrote:
> > Very good approach, I will start moving light checks from _GLIBCXX_DEBUG
> > implementation to normal one then.
>
> Great, thanks. I *think* my patch got most of the lightweight checks
> already.
>
> We could maybe include the irreflexivity checks, although it does
> change the number of calls to the comparison function, which is not
> allowed for some algorithms.
>
> I'll commit my patch today.

I've committed the attached patch to trunk. It's the same as the
original one except for the tweaks to the docs in response to Daniel's
comment, and some whitespace changes in <valarray>.

I haven't made _FORTIFY_SOURCE enable these yet.

Tested powerpc64le-linux.

Here are some patches we should consider merging from the google
branches:

https://gcc.gnu.org/ml/gcc-patches/2015-08/msg00008.html
https://gcc.gnu.org/ml/gcc-patches/2014-01/msg00215.html
https://gcc.gnu.org/ml/gcc-patches/2013-09/msg01837.html
https://gcc.gnu.org/ml/gcc-patches/2013-05/msg01817.html
https://gcc.gnu.org/ml/gcc-patches/2013-01/msg01074.html
https://gcc.gnu.org/ml/gcc-patches/2013-01/msg01186.html

(The last two probably only work for unoptimized builds, but that may
still be useful).

Those are just ones I had in my mailbox, we should search for
__google_stl to find them all. Each should be considered individually,
I know I disliked some of the early patches when I first looked at
them years ago.

Discussion about enabling these checks automatically:
https://gcc.gnu.org/ml/gcc-paetches/2013-05/msg01386.html
https://gcc.gnu.org/ml/gcc-patches/2013-06/msg00211.html

I'd forgotten about Oleg's suggestion of _GLIBCXX_DEBUG_LEVEL_N:
https://gcc.gnu.org/ml/libstdc++/2014-06/msg00107.html
ANother option would be to support different checks depending on the
value of _GLIBCXX_ASSERTIONS=N, but I think for now we should keep it
simple and not complicate things like that. If these checks are light
enough then I think we only need two levels: cheap assertions and full
debug mode.

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