CVS commit: src/lib/libc/gen

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Sun Mar  2 22:46:24 UTC 2025

Modified Files:
        src/lib/libc/gen: arc4random.c pthread_atfork.c

Log Message:
libc: New __libc_atfork.

This uses caller-provided storage for the callback queues.

Use it in arc4random(3) in order to avoid possible failure modes.

This is a private symbol, not designed for use outside NetBSD, and
the API is not intended to be stable (yet) -- I just took the
existing purely internal structure (struct atfork_callback) and
reused it for this API without changing any of the calling-side
logic.  We could change it, e.g. to use a single structure per call,
to make the API a little less unwieldy, at the cost of
microscopically more storage and runtime for the users that don't use
all three callbacks; to be considered in a future change.

We might reasonably use __libc_atfork in libpthread for use in the
pthread_tsd_init constructor, in order to be confident it never
attempts malloc(3), but let's do that in a separate commit just in
case anything goes awry with that plan.

PR lib/59112: libpthread constructors use malloc
PR lib/59117: arc4random has some failure modes it shouldn't


To generate a diff of this commit:
cvs rdiff -u -r1.39 -r1.40 src/lib/libc/gen/arc4random.c
cvs rdiff -u -r1.23 -r1.24 src/lib/libc/gen/pthread_atfork.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.