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Add WebAssembly/TypeScript bindings (Z3Prover#5762)
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* Add TypeScript bindings

* mark Z3_eval_smtlib2_string as async
bakkot authored Jan 10, 2022
1 parent 9ac57fc commit 2b934b6
Showing 18 changed files with 1,724 additions and 35 deletions.
61 changes: 61 additions & 0 deletions .github/workflows/wasm-release.yml
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name: WebAssembly Publish

on:
workflow_dispatch:

defaults:
run:
working-directory: src/api/js

env:
EM_VERSION: 3.1.0

jobs:
publish:
name: Publish
runs-on: ubuntu-latest
steps:
- name: Checkout
uses: actions/checkout@v2

- name: Setup node
uses: actions/setup-node@v2
with:
node-version: 'lts/*'
registry-url: 'https://registry.npmjs.org'

- name: Prepare for publish
run: |
npm version $(node -e 'console.log(fs.readFileSync("../../../scripts/release.yml", "utf8").match(/ReleaseVersion:\s*\x27(\S+)\x27/)[1])')
mv PUBLISHED_README.md README.md
cp ../../../LICENSE.txt .
- name: Setup emscripten
uses: mymindstorm/setup-emsdk@v11
with:
no-install: true
version: ${{env.EM_VERSION}}
actions-cache-folder: 'emsdk-cache'

- name: Install dependencies
run: npm ci

- name: Build TypeScript
run: npm run build-ts

- name: Build wasm
run: |
emsdk install ${EM_VERSION}
emsdk activate ${EM_VERSION}
source $(dirname $(which emsdk))/emsdk_env.sh
which node
which clang++
npm run build-wasm
- name: Test
run: npm test

- name: Publish
run: npm publish
env:
NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
74 changes: 41 additions & 33 deletions .github/workflows/wasm.yml
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@@ -1,43 +1,51 @@
name: WASM Build
name: WebAssembly Build

on:
push:
branches: [ master ]
pull_request:

defaults:
run:
working-directory: src/api/js

env:
BUILD_TYPE: Release
EM_VERSION: 3.1.0

jobs:
build:
check:
name: Check
runs-on: ubuntu-latest

steps:
- name: Checkout code
uses: actions/checkout@v2

- name: Import emscripten
uses: mymindstorm/setup-emsdk@v9

- name: Configure CMake and build
run: |
mkdir build
cd build
emcmake cmake \
-DCMAKE_BUILD_TYPE=MinSizeRel \
-DZ3_BUILD_LIBZ3_SHARED=OFF \
-DZ3_ENABLE_EXAMPLE_TARGETS=OFF \
-DZ3_BUILD_TEST_EXECUTABLES=OFF \
-DZ3_BUILD_EXECUTABLE=OFF \
-DZ3_SINGLE_THREADED=ON \
-DCMAKE_CXX_FLAGS="-s DISABLE_EXCEPTION_CATCHING=0" \
..;
make
tar -cvf z3-build-wasm.tar *.a
- name: Archive production artifacts
uses: actions/upload-artifact@v2
with:
name: z3-build-wasm
path: build/z3-build-wasm.tar
retention-days: 5
- name: Checkout
uses: actions/checkout@v2

- name: Setup node
uses: actions/setup-node@v2
with:
node-version: 'lts/*'

- name: Setup emscripten
uses: mymindstorm/setup-emsdk@v11
with:
no-install: true
version: ${{env.EM_VERSION}}
actions-cache-folder: 'emsdk-cache'

- name: Install dependencies
run: npm ci

- name: Build TypeScript
run: npm run build-ts

- name: Build wasm
run: |
emsdk install ${EM_VERSION}
emsdk activate ${EM_VERSION}
source $(dirname $(which emsdk))/emsdk_env.sh
which node
which clang++
npm run build-wasm
- name: Test
run: npm test
7 changes: 7 additions & 0 deletions .gitignore
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@@ -75,6 +75,13 @@ src/api/ml/z3enums.ml
src/api/ml/z3native.mli
src/api/ml/z3enums.mli
src/api/ml/z3.mllib
src/api/js/node_modules/
src/api/js/*.js
src/api/js/build/
src/api/js/**/*.d.ts
!src/api/js/scripts/*.js
!src/api/js/src/*.js

out/**
*.bak
doc/api
4 changes: 2 additions & 2 deletions README.md
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@@ -195,9 +195,9 @@ See [``examples/python``](examples/python) for examples.

The Julia package [Z3.jl](https://github.com/ahumenberger/Z3.jl) wraps the C++ API of Z3. Information about updating and building the Julia bindings can be found in [src/api/julia](src/api/julia).

### ``Web Assembly``
### ``Web Assembly`` / ``TypeScript`` / ``JavaScript``

[WebAssembly](https://github.com/cpitclaudel/z3.wasm) bindings are provided by Clément Pit-Claudel.
A WebAssembly build with associated TypeScript typings is published on npm as [z3-solver](https://www.npmjs.com/package/z3-solver). Information about building these bindings can be found in [src/api/js](src/api/js).

## System Overview

124 changes: 124 additions & 0 deletions src/api/js/PUBLISHED_README.md
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# Z3 TypeScript Bindings

This project provides low-level TypeScript bindings for the [Z3 theorem prover](https://github.com/Z3Prover/z3). It is available on npm as [z3-solver](https://www.npmjs.com/package/z3-solver).

Z3 itself is distributed as a wasm artifact as part of this package. You can find the documentation for the Z3 API [here](https://z3prover.github.io/api/html/z3__api_8h.html), though note the differences below.


## Using

This requires threads, which means you'll need to be running in an environment which supports `SharedArrayBuffer`. In browsers, in addition to ensuring the browser has implemented `SharedArrayBuffer`, you'll need to serve your page with [special headers](https://web.dev/coop-coep/). There's a [neat trick](https://github.com/gzuidhof/coi-serviceworker) for doing that client-side on e.g. Github Pages, though you shouldn't use that trick in more complex applications.

Other than the differences below, the bindings can be used exactly as you'd use the C library. Because this is a wrapper around a C library, most of the values you'll use are just numbers representing pointers. For this reason you are strongly encouraged to make use of the TypeScript types to differentiate among the different kinds of value.

The module exports an `init` function, is an async function which initializes the library and returns `{ em, Z3 }` - `em` contains the underlying emscripten module, which you can use to e.g. kill stray threads, and `Z3` contains the actual bindings. The other module exports are the enums defined in the Z3 API.

[`test-ts-api.ts`](./test-ts-api.ts) contains a couple real cases translated very mechanically from [this file](https://github.com/Z3Prover/z3/blob/90fd3d82fce20d45ed2eececdf65545bab769503/examples/c/test_capi.c).


## Differences from the C API

### Integers

JavaScript numbers are IEEE double-precisions floats. These can be used wherever the C API expects an `int`, `unsigned int`, `float`, or `double`.

`int64_t` and `uint64_t` cannot be precisely represented by JS numbers, so in the TS bindings they are represented by [BigInts](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#bigint_type).

### Out parameters

In C, to return multiple values a function will take an address to write to, conventionally referred to as an "out parameter". Sometimes the function returns a boolean to indicate success; other times it may return nothing or some other value.

In JS the convention when returning multiple values is to return records containing the values of interest.

The wrapper translates between the two conventions. For example, the C declaration

```c
void Z3_rcf_get_numerator_denominator(Z3_context c, Z3_rcf_num a, Z3_rcf_num * n, Z3_rcf_num * d);
```
is represented in the TS bindings as
```ts
function rcf_get_numerator_denominator(c: Z3_context, a: Z3_rcf_num): { n: Z3_rcf_num; d: Z3_rcf_num } {
// ...
}
```

When there is only a single out parameter, and the return value is not otherwise of interest, the parameter is not wrapped. For example, the C declaration

```c
Z3_bool Z3_model_eval(Z3_context c, Z3_model m, Z3_ast t, bool model_completion, Z3_ast * v);
```
is represented in the TS bindings as
```ts
function model_eval(c: Z3_context, m: Z3_model, t: Z3_ast, model_completion: boolean): Z3_ast | null {
// ...
}
```

Note that the boolean return type of the C function is translated into a nullable return type for the TS binding.

When the return value is of interest it is included in the returned record under the key `rv`.


### Arrays

The when the C API takes an array as an argument it will also require a parameter which specifies the length of the array (since arrays do not carry their own lengths in C). In the TS bindings this is automatically inferred.

For example, the C declaration
```js
unsigned Z3_rcf_mk_roots(Z3_context c, unsigned n, Z3_rcf_num const a[], Z3_rcf_num roots[]);
```
is represented in the TS bindings as
```ts
function rcf_mk_roots(c: Z3_context, a: Z3_rcf_num[]): { rv: number; roots: Z3_rcf_num[] } {
// ...
}
```
When there are multiple arrays which the C API expects to be of the same length, the TS bindings will enforce that this is the case.
### Null pointers
Some of the C APIs accept or return null pointers (represented by types whose name end in `_opt`). These are represented in the TS bindings as `| null`. For example, the C declaration
```js
Z3_ast_opt Z3_model_get_const_interp(Z3_context c, Z3_model m, Z3_func_decl a);
```
is represented in the TS bindings as
```ts
function model_get_const_interp(c: Z3_context, m: Z3_model, a: Z3_func_decl): Z3_ast | null {
// ...
}
```
### Async functions
Certain long-running APIs are not appropriate to call on the main thread. In the TS bindings those APIs are marked as `async` and are automatically called on a different thread. This includes the following APIs:
- `Z3_simplify`
- `Z3_simplify_ex`
- `Z3_solver_check`
- `Z3_solver_check_assumptions`
- `Z3_solver_cube`
- `Z3_solver_get_consequences`
- `Z3_tactic_apply`
- `Z3_tactic_apply_ex`
- `Z3_optimize_check`
- `Z3_algebraic_roots`
- `Z3_algebraic_eval`
- `Z3_fixedpoint_query`
- `Z3_fixedpoint_query_relations`
- `Z3_fixedpoint_query_from_lvl`
- `Z3_polynomial_subresultants`
Note that these are not thread-safe, and so only one call can be running at a time. Trying to call a second async API before the first completes will throw.
17 changes: 17 additions & 0 deletions src/api/js/README.md
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# TypeScript Bindings

This directory contains JavaScript code to automatically derive TypeScript bindings for the C API, which are published on npm as [z3-solver](https://www.npmjs.com/package/z3-solver).

The readme for the bindings themselves is located in [`PUBLISHED_README.md`](./PUBLISHED_README.md).


## Building

You'll need to have emscripten set up, along with all of its dependencies. The easiest way to do that is with [emsdk](https://github.com/emscripten-core/emsdk).

Then run `npm i` to install dependencies, `npm run build-ts` to build the TypeScript wrapper, and `npm run build-wasm` to build the wasm artifact.


## Tests

Current tests are very minimal: [`test-ts-api.ts`](./test-ts-api.ts) contains a couple real cases translated very mechanically from [this file](https://github.com/Z3Prover/z3/blob/90fd3d82fce20d45ed2eececdf65545bab769503/examples/c/test_capi.c).
23 changes: 23 additions & 0 deletions src/api/js/build-wasm.sh
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#!/bin/bash

set -euxo pipefail


export ROOT=$PWD

cd ../../..
export CXXFLAGS="-pthread -s USE_PTHREADS=1 -s DISABLE_EXCEPTION_CATCHING=0"
export LDFLAGS="-s WASM_BIGINT -s -pthread -s USE_PTHREADS=1"
if [ ! -f "build/Makefile" ]; then
emconfigure python scripts/mk_make.py --staticlib --single-threaded
fi

cd build
emmake make -j$(nproc) libz3.a

cd $ROOT

export EM_CACHE=$HOME/.emscripten/
export FNS=$(node scripts/list-exports.js)
export METHODS='["ccall","FS","allocate","UTF8ToString","intArrayFromString","ALLOC_NORMAL"]'
emcc build/async-fns.cc ../../../build/libz3.a --std=c++20 --pre-js src/async-wrapper.js -g2 -pthread -fexceptions -s WASM_BIGINT -s USE_PTHREADS=1 -s PTHREAD_POOL_SIZE=0 -s PTHREAD_POOL_SIZE_STRICT=0 -s MODULARIZE=1 -s 'EXPORT_NAME="initZ3"' -s EXPORTED_RUNTIME_METHODS=$METHODS -s EXPORTED_FUNCTIONS=$FNS -s DISABLE_EXCEPTION_CATCHING=0 -s SAFE_HEAP=0 -s DEMANGLE_SUPPORT=1 -s TOTAL_MEMORY=1GB -I z3/src/api/ -o build/z3-built.js
57 changes: 57 additions & 0 deletions src/api/js/example-raw.ts
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import { init } from './build/wrapper';

// demonstrates use of the raw API

(async () => {
let { em, Z3 } = await init();

Z3.global_param_set('verbose', '10');
console.log('verbosity:', Z3.global_param_get('verbose'));

let config = Z3.mk_config();
let ctx = Z3.mk_context_rc(config);
Z3.del_config(config);

let unicodeStr = [...'hello™'].map(x => x.codePointAt(0)!);
let strAst = Z3.mk_u32string(ctx, unicodeStr);
Z3.inc_ref(ctx, strAst);

console.log(Z3.is_string(ctx, strAst));
console.log(Z3.get_string(ctx, strAst));
console.log(Z3.get_string_contents(ctx, strAst, unicodeStr.length));

let bv = Z3.mk_bv_numeral(ctx, [true, true, false]);
let bs = Z3.mk_ubv_to_str(ctx, bv);
console.log(Z3.ast_to_string(ctx, bs));

let intSort = Z3.mk_int_sort(ctx);
let big = Z3.mk_int64(ctx, 42n, intSort);
console.log(Z3.get_numeral_string(ctx, big));
console.log(Z3.get_numeral_int64(ctx, big));

console.log(Z3.get_version());

let head_tail = [Z3.mk_string_symbol(ctx, 'car'), Z3.mk_string_symbol(ctx, 'cdr')];

let nil_con = Z3.mk_constructor(ctx, Z3.mk_string_symbol(ctx, 'nil'), Z3.mk_string_symbol(ctx, 'is_nil'), [], [], []);
let cons_con = Z3.mk_constructor(
ctx,
Z3.mk_string_symbol(ctx, 'cons'),
Z3.mk_string_symbol(ctx, 'is_cons'),
head_tail,
[null, null],
[0, 0],
);

let cell = Z3.mk_datatype(ctx, Z3.mk_string_symbol(ctx, 'cell'), [nil_con, cons_con]);
console.log(Z3.query_constructor(ctx, nil_con, 0));
console.log(Z3.query_constructor(ctx, cons_con, 2));

Z3.dec_ref(ctx, strAst);
Z3.del_context(ctx);

em.PThread.terminateAllThreads();
})().catch(e => {
console.error('error', e);
process.exit(1);
});
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