dlopen: expose the main program symbol scope

[brandonpayton]

Why

Dynamic loading lets a running program open a shared module and look up symbols by name. GNU Make uses this for plugins. dlopen(NULL) represents the main executable, while RTLD_DEFAULT asks the loader to search the program's default symbol scope.

GNU Make and other plugin hosts use dlopen(NULL, ...) and dlsym(RTLD_DEFAULT, ...) to expose executable symbols to loaded modules. Kandelo's libc glue hard-coded dlopen(NULL) as unsupported even though the shared host runtime already records the main Wasm instance's exported function and data symbols.

This is the platform root cause behind GNU Make needing --disable-load; leaving that configure switch in a package formula would hide a Kandelo dynamic-linking gap.

What changed

• Reserve a stable opaque handle for the main program without changing the existing __wasm_dlopen import signature.
• Resolve exported functions to indirect-table indices and exported data globals to linear-memory addresses for both the main handle and RTLD_DEFAULT.
• Keep side-module handles disjoint and preserve deterministic fork replay ordering.
• Exercise the same compiled C fixture through Node and Chromium, including function and data lookup.
• Document --export-dynamic, default symbol visibility, and the remaining RTLD_NEXT limitation.

Host parity

host/src/worker-main.ts is the shared Node/browser process worker path. The new fixture passes through CentralizedKernelHost on Node and BrowserKernel in Chromium; neither host has a separate compatibility path.

ABI and artifacts

This is a backward-compatible semantic addition over the existing host import signature. No channel layout, import signature, kernel export, generated binding, or snapshot entry changed, and existing binaries remain valid. ABI_VERSION therefore remains 18 under the additive-within-an-epoch policy.

No package archives, indexes, VFS images, or committed Wasm artifacts are changed. Programs that use the new behavior must be rebuilt with the current libc glue and run with the current host, as with other additive changes in an ABI epoch.

Validation

On the rebased ABI 18 head:

• ./scripts/dev-shell.sh bash scripts/build-musl.sh
• ./scripts/dev-shell.sh bash -c 'cargo build --release -p kandelo -Z build-std=core,alloc'
• ./scripts/dev-shell.sh npm --prefix host test -- --run test/dylink.test.ts test/dlopen-e2e.test.ts test/fork-dlopen-replay-e2e.test.ts (22 tests passed after installing the current kernel; the first attempt failed only because local-binaries/kernel.wasm was absent)
• ./scripts/dev-shell.sh npm --prefix host run typecheck
• ./scripts/dev-shell.sh bash scripts/check-abi-version.sh
• git diff --check origin/main...HEAD

The same Chromium fixture passed on the pre-rebase semantic head. On the rebased head, local fetch-only setup correctly rejected the released node archive because rebuilding libc changes the package cache key. I did not bypass that check or source-build this incidental browser-demo dependency; hosted staging must rebuild the affected package graph and rerun the Chromium suite on this exact head.

I did not run the full host, browser, libc-test, POSIX, or Sortix suites locally. libc-test explicitly skips its DSO/dlopen .mk cases, while the added end-to-end fixture directly covers this glue and host path.

Remaining boundary

RTLD_NEXT lookup remains unsupported and is documented as such.

[github-actions]

Phase B-1 matrix build status — pr-879-staging

ABI v18. 69 built, 0 failed, 69 total.

Package	Arch	Status	Sha
libcurl	wasm32	built	a7ec8384
libcxx	wasm32	built	09c06607
libcxx	wasm64	built	d5709528
libpng	wasm32	built	47444054
libxml2	wasm32	built	993a7a2c
libxml2	wasm64	built	c8f4e029
openssl	wasm32	built	d2fc84e8
openssl	wasm64	built	985da291
sqlite	wasm32	built	6b0137a9
sqlite	wasm64	built	4825f6a1
zlib	wasm32	built	e9fdd5b1
zlib	wasm64	built	1c77cf7b
bc	wasm32	built	85ddd078
bzip2	wasm32	built	fc8c7fb4
coreutils	wasm32	built	a8e4d1f7
curl	wasm32	built	e5be2304
dash	wasm32	built	31be600e
diffutils	wasm32	built	ec140b77
dinit	wasm32	built	88603967
fbdoom	wasm32	built	95fede2e
file	wasm32	built	d652f794
findutils	wasm32	built	a5fd70de
gawk	wasm32	built	977c32f0
git	wasm32	built	50e7bf19
grep	wasm32	built	a7e0cfd5
gzip	wasm32	built	c7e2e85f
hello	wasm32	built	65e2176c
kandelo-sdk	wasm32	built	c6ff9328
kernel	wasm32	built	4844b391
less	wasm32	built	c5939334
lsof	wasm32	built	2f1c6304
m4	wasm32	built	f552cabe
make	wasm32	built	26155b53
mariadb	wasm32	built	f861a897
mariadb	wasm64	built	3c4aa9de
modeset	wasm32	built	7f3bcc5a
msmtpd	wasm32	built	1f8d13ee
nano	wasm32	built	f5d649f5
ncurses	wasm32	built	dc9ea43f
netcat	wasm32	built	fdbc86ec
nginx	wasm32	built	ef785fc2
php	wasm32	built	d103a42f
posix-utils-lite	wasm32	built	587aa7b5
ruby	wasm32	built	4ff5cc56
sed	wasm32	built	7177e695
spidermonkey	wasm32	built	43de30ca
tar	wasm32	built	debfa58a
tcl	wasm32	built	dd1a64f9
unzip	wasm32	built	d3254898
userspace	wasm32	built	2ff5a537
vim	wasm32	built	b6cacaf9
wget	wasm32	built	47794347
xz	wasm32	built	60075411
zip	wasm32	built	57fc3ddd
zstd	wasm32	built	75e9bd9e
bash	wasm32	built	7280a58f
mariadb-test	wasm32	built	dc75215f
mariadb-vfs	wasm32	built	1afaa3af
mariadb-vfs	wasm64	built	13215777
nethack	wasm32	built	9e34b035
node	wasm32	built	598f6735
spidermonkey-node	wasm32	built	0e109cc0
vim-browser-bundle	wasm32	built	62ea9614
nethack-browser-bundle	wasm32	built	15edeab6
rootfs	wasm32	built	6f214852
shell	wasm32	built	24b8e787
lamp	wasm32	built	4832a8bf
node-vfs	wasm32	built	357db97e
wordpress	wasm32	built	bceb6b71

_{Auto-generated; replaced on each push. Raw data in the publish-status workflow artifact.}

[brandonpayton]

Absorbed by rebase-merged #967. Main is now 6efb411 with the sealed tree b133bfa018f7e2bc84c4845edf2f945b2f844954, and ABI 41 activation completed successfully in run 29550069085. The absorption audit confirmed this PR\x27s behavior and tests are present in that merged tree, so this source PR is closed and its branch is deleted.