Re: Would an increase to PTHREAD_KEYS_MAX be an example of a FreeBSD ABI change? (lang/rust involved in why I ask)

On 5/14/26 11:30, Mark Millard wrote:
> Would an increase to PTHREAD_KEYS_MAX be an example of a FreeBSD ABI change?
> 
> 
> Why I ask: an active failure for at least rust use on armv7 . . .
> 
> The armv7 1.94.0 rust-bootstrap used to try to build 1.95.0 of lang/rust
> for armv7 gets the Thread Local Storage failure "Out of TLS keys".
> 
> The same was true for the armv7 1.93.0 rust-bootstrap used to try to
> build the armv7 1.94.0:
> 
> <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=294545>
> (Robert Clausecker, not me.)
> 
> 
> OpenBSD increased PTHREAD_KEYS_MAX to 512 to avoid getting such "Out of
> TLS keys" failures, not necessarily for armv7 or for building rustc:
> 
> <https://github.com/openbsd/src/commit/f90c65410264d8346b711e36bca7ee1f0dde5ca9>
> (2025-11-11)
> 
> QUOTE from OpenBSD's commit:
> bump PTHREAD_KEYS_MAX to 512
> the rust libstd emutls version is using one pthread_key per
> thread-variable. it means the maximum number of thread-variable at a
> time is PTHREAD_KEYS_MAX.
> 
> with recent rustc 1.91.0, we start hiting the limit while compiling some
> programs (like sysutils/rustic).
> 
> ok robert@
> "Let's go 512 and hope someone eventually does proper TLS" deraadt@
> END QUOTE
> 
> I think they had 256 previous to the change, not just 128.
> 
> (The "libstd emutls version" may not be always involved for rust's
> context? Also: the failure type is apparently not limited to building
> the rust compiler/toolchain. The overall issue is not FreeBSD OS specific.)
> 
> 
> Note: It appears that the official FreeBSD port-package building for
> armv7 stopped shortly before this started to be an issue. That is why
> fallout reports have not been accumulating for the "out of TLS keys" issue.
> 
> 
> If increasing PTHREAD_KEYS_MAX is an ABI change, an implication is that
> 14.*-RELEASE and 15.*-RELEASE could not be changed, possibly eliminating
> rust use on armv7 going forward.
> 
> 
> Note:
> It is my understanding that alternate Thread Local Storage models for
> rust require use of rust-nightly (unstable) builds instead of stable
> rust builds.
> 
> 

[Replied to original to associate with the overall problem, without lots
of other detail.]

There seems to be confusion on if rust 1.95.0 is fixed vs. improved for
the "out of TLS keys" issue. I'll quote another OS's results on that:

<https://github.com/rust-lang/rust/issues/155758#issuecomment-4351327231>

QUOTE
. . . Rust 1.95.0 does improve the situation on Haiku, but it does not
fully fix it. With 1.95.0, some packages that failed for me on 1.94.1
now build successfully. However, I still have packages that fail with
the same fatal error on 1.95.0, while those same packages build
successfully with 1.89.0.
END QUOTE

(Haiku jumped from 1.89.0 to 1.94.1 to 1.95.0, skipping all the
1.9[0123].0 .)


-- 
===
Mark Millard
marklmi at yahoo.com