[paul-hammant]

Two JavaScript-hosting changes, drafted by Jules (paul-hammant#45, merged here unchanged) and shaped in the commit on top.

Duktape gets Lua's bidirectional embedding API (#904): a persistent VM, Aether callbacks the script calls by dotted name (vm_register(vm, "app.math.add", fn)), typed arguments and returns, global setters, and typed eval results with Lua's type tags. contrib.host.js (its alias) gets the same. vm_set_instruction_limit honestly reports the limit unavailable: the system libduktape this host loads is built without DUK_USE_EXEC_TIMEOUT_CHECK (checked against Debian's 2.7.0 duk_config.h).

QuickJS joins the contrib/host family. contrib.host.quickjs wraps contrib.quickjs with the surface every host shares: run, run_sandboxed, run_sandboxed_with_map, init, finalize. The engine has no file, network or OS access of its own, so grants decide only what the Aether host functions a script calls may do. contrib.quickjs's API is unchanged (sae depends on it).

What the shaping commit fixes

Duktape:

• raise_error threw at once, longjmp-ing out of the Aether callback past its defers. It now returns a sentinel and the trampoline throws after the callback has returned.
• The trampoline passed the callback's return straight to Duktape, where 2+ is invalid and a negative value is an error code. It now returns 0 or 1.
• vm_result_int / arg_int cast NaN or out-of-range numbers to int64_t, which is undefined behaviour. They now read 0 or saturate.
• throw "x" read as a string result; it now reads as an error.
• vm_register silently truncated names of 256+ characters; it now refuses them.
• The spec's string-list global was built as an int array, so its assertion failed. The integration script SKIPped on a machine with libduktape installed (pkg-config prints no flags for /usr/include), and turned a failed harness build into a SKIP; both fixed.

QuickJS:

• A program importing only contrib.host.quickjs failed to link, the new example included. The module now imports contrib.quickjs, whose @source compiles the engine in. (check-examples only type-checks host examples, so it didn't notice.)
• The C used qjs_global / qjs_set undeclared, an error under Apple clang and GCC 14.
• The test named "run_sandboxed enforces sandbox grants" never called run_sandboxed. It's renamed for what it checks, and a new case checks that both wrappers leave the grant stack as they found it, also when the script throws.

Docs, the QuickJS README's claim about grants, and the changelog fragments are corrected.

Checked

• Every fix above was undone once and its test failed (five Duktape fixes, two missing grant pops, the trampoline in the integration script); restored, all pass.
• Duktape spec 7 passing, QuickJS spec 6 passing, both valgrind-clean (0 errors, 0 definitely lost). The Duktape integration script passes.
• make contrib-host-check: aether 6, duktape 7, lua 5, perl 5, python 5, quickjs 6.
• ae fmt, check-docs, check-changelog, check-tests, check-warnings, check-raw-calls, check-extern-widths, check-standalone, check-crypto-wipe, check-archive-exports-nozlib pass; check-examples passes apart from a local untracked build artifact.
• Both host C files compile clean under -Wall -Wextra -Werror (QuickJS) and with no implicit declarations (Duktape).

For the maintainers

contrib.host.js still aliases Duktape (ES5, system library). Whether it should point at QuickJS (ES2023, compiled in, no ambient OS access, the engine sae chose) is left open.

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