Re: [PATCH v2 2/3] ci: add build checking for side-effects in assert() calls

From: Taylor Blau <me@ttaylorr.com>
Date: Mar 17, 2025, 22:30 UTC
Message-ID: <Z9iinbyrn4PeFmCl@nand.local>
In-Reply-To: <58cb8f6a1609b10d761e86bdad541d1c018cb582.1742107322.git.gitgitgadget@gmail.com>

On Sun, Mar 16, 2025 at 06:42:01AM +0000, Elijah Newren via GitGitGadget wrote:

Show 14 quoted lines

> We have roughly 566 assert() calls in our codebase (my grep might have
> picked up things that aren't actually assert() calls, but most appeared
> to be).  All but 9 of them can be determined by gcc to be free of side
> effects with a clever redefine of assert() provided by Bruno De Fraine
> (from
> https://stackoverflow.com/questions/10593492/catching-assert-with-side-effects),
> who upon request has graciously placed his two-liner into the public
> domain without warranty of any kind.  The current 9 assert() calls
> flagged by this clever redefinition of assert() appear to me to be free
> of side effects as well, but are too complicated for a compiler/linker
> to figure that since each assertion involves some kind of function call.
> Add a CI job which will find and report these possibly problematic
> assertions, and have the job suggest to the user that they replace these
> with BUG_IF_NOT() calls.

Very nice, and thank you Bruno for placing your very clever assert() in the public domain :-).

I wonder if it might be useful to explain this in Documentation/CodingGuidelines as a follow-up to this series. I was thinking of a scenario where someone either writes a side-effecting assert(), or a non-side-effecting one that is too complicated to prove otherwise.

If that person runs 'make test' locally, they might not see any failures, but then be surprised when CI fails on the new step. It may be worth mentioning that we have such a check, and that we expect all assert() statements to be side effect-free, and that developers can verify this by ci/check-unsafe-assertions.sh.

But that may bring us into an assert() versus BUG_IF_NOT() debate, which may be somewhat counterproductive, so I'm just as happy if you did nothing here :-).

Thanks, Taylor