Add hooks for statically linking extensions into the WASI build - #87
Open
bendytree wants to merge 2 commits into
Open
Add hooks for statically linking extensions into the WASI build#87bendytree wants to merge 2 commits into
bendytree wants to merge 2 commits into
Conversation
added 2 commits
August 26, 2026 10:31
dltab was a tentative one-element array ("dict_t* dltab[]") indexed past
its end, and slot 0 was never assigned: the first library was stored at
dltab[1] while the lookup loop read dltab[0..dltab_index). Every dlopen
lookup therefore dereferenced a NULL dict, i.e. guest address 0.
That happens to be harmless while address 0 holds zeros (the dict's len
field reads as 0), which is why the socket-file transport never noticed.
With the CMA wire channel, live request bytes sit at the bottom of linear
memory, so the NULL-dict read picks up garbage lengths and entry pointers
and traps — reproducible as a crash on the first CREATE EXTENSION issued
over CMA.
Make dltab a real fixed-size array, keep every slot initialized, check
the existing-library branch against index >= 0 (slot 0 is valid), and
return stable 1-based handles.
The WASI flavor has no dynamic loading; its dlopen shim resolves symbols
from a hardcoded table covering only dict_snowball and plpgsql, so
extensions like pgvector cannot be added without editing the shim.
Add two overridable (weak) hooks:
- pglite_extra_dlsym(symbol): consulted when the built-in table misses,
letting a linked object supply extension symbols (e.g. a table
generated from llvm-nm over the extension's static library);
- pglite_extra_dlopen(filename): called for every dlopen, letting the
object run the extension's renamed _PG_init.
Also pass ${EXTRA_PG_LIBS:-} at the end of the pglite.wasi link line so
a build can append static extension archives without patching build.sh.
The weak defaults keep the stock build byte-identical in behavior.
Used to link pgvector 0.8.0 (with a 327-entry generated dlsym table)
into pglite.wasi; CREATE EXTENSION vector, the vector type, distance
operators, and HNSW/IVFFlat index builds all work, verified natively on
iOS/macOS and under wazero/node WASI hosts.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The WASI flavor has no dynamic loading; its dlopen shim resolves symbols from a hardcoded table covering only
dict_snowballandplpgsql, so extensions can't be added without editing the shim.This PR adds two overridable (weak) hooks to
sdk_port-wasi-dlfcn.c:pglite_extra_dlsym(symbol)— consulted when the built-in table misses, so a linked object can supply extension symbols (e.g. a table generated fromllvm-nmover the extension's static archive);pglite_extra_dlopen(filename)— called on every dlopen, so that object can run the extension's (renamed)_PG_init.…and passes
${EXTRA_PG_LIBS:-}at the end of thepglite.wasilink line inpglite-wasm/build.sh, so a build can append static extension archives without patching the script. The weak defaults keep the stock build's behavior unchanged.I use this to link pgvector 0.8.0 into
pglite.wasi(renaming_PG_init/Pg_magic_funcvia-Dto avoid colliding with plpgsql's statically linked copies, plus a 327-entry generated dlsym table).CREATE EXTENSION vector, thevectortype, distance operators, and HNSW/IVFFlat index builds all work — verified under node/wazero WASI hosts and in a native wasm2c iOS embedding (https://github.com/bendytree/pglite-ios), where the full build recipe lives inmodule/.Note: includes the commit from #86 (the dlopen fix) as its base, since both touch
dlopen().