Add examples of linking and WASI (#1369)

* Add examples of linking and WASI

This commit adds two example programs, one for linking two modules
together and one for instantiating WASI. The linkage example
additionally uses WASI to get some meaningful output at this time.

cc #1272

* Add examples to the book as well

* More links!

* Ignore examples from rustdoc testsing

* More example updates

* More ignored

Author: alexcrichton

Cargo.lock

@@ -67,6 +67,7 @@ members = [
   "crates/misc/rust",
   "crates/wiggle",
   "examples/fib-debug/wasm",
+  "examples/wasi/wasm",
   "fuzz",
 ]
 

Cargo.toml

@@ -2,13 +2,18 @@ use std::collections::BTreeSet;
 use std::process::Command;
 
 fn main() {
+    let example_to_run = std::env::args().nth(1);
     let examples = std::fs::read_dir("examples").unwrap();
     let examples = examples
-        .map(|e| {
+        .filter_map(|e| {
             let e = e.unwrap();
             let path = e.path();
             let dir = e.metadata().unwrap().is_dir();
-            (path.file_stem().unwrap().to_str().unwrap().to_owned(), dir)
+            if let Some("wat") = path.extension().and_then(|s| s.to_str()) {
+                return None;
+            }
+
+            Some((path.file_stem().unwrap().to_str().unwrap().to_owned(), dir))
         })
         .collect::<BTreeSet<_>>();
 
@@ -21,14 +26,24 @@ fn main() {
         if example == "README" {
             continue;
         }
+        if let Some(example_to_run) = &example_to_run {
+            if !example.contains(&example_to_run[..]) {
+                continue;
+            }
+        }
         if is_dir {
             println!("======== Rust wasm file `{}` ============", example);
+            let target = if example == "fib-debug" {
+                "wasm32-unknown-unknown"
+            } else {
+                "wasm32-wasi"
+            };
             run(Command::new("cargo")
                 .arg("build")
                 .arg("-p")
                 .arg(format!("example-{}-wasm", example))
                 .arg("--target")
-                .arg("wasm32-unknown-unknown"));
+                .arg(target));
         }
         println!("======== Rust example `{}` ============", example);
         run(Command::new("cargo")

crates/misc/run-examples/src/main.rs

@@ -7,6 +7,22 @@
 - [Examples](./examples.md)
   - [Markdown parser](./examples-markdown.md)
   - [Profiling WebAssembly](./examples-profiling.md)
+  - [Embedding in Rust](./examples-rust-embed.md)
+    - [Hello, world!](./examples-rust-hello-world.md)
+    - [Calculating the GCD](./examples-rust-gcd.md)
+    - [Using linear memory](./examples-rust-memory.md)
+    - [WASI](./examples-rust-wasi.md)
+    - [Linking modules](./examples-rust-linking.md)
+    - [Debugging](./examples-rust-debugging.md)
+    - [Using multi-value](./examples-rust-multi-value.md)
+  - [Embedding in C](./examples-c-embed.md)
+    - [Hello, world!](./examples-c-hello-world.md)
+    - [Calculating the GCD](./examples-c-gcd.md)
+    - [Using linear memory](./examples-c-memory.md)
+    - [WASI](./examples-c-wasi.md)
+    - [Linking modules](./examples-c-linking.md)
+    - [Debugging](./examples-c-debugging.md)
+    - [Using multi-value](./examples-c-multi-value.md)
 - [Using WebAssembly from your lanugage](./lang.md)
   - [Python](./lang-python.md)
   - [.NET](./lang-dotnet.md)

docs/SUMMARY.md

@@ -3,7 +3,8 @@
 This document shows an example of how to embed Wasmtime using the [Rust
 API][apidoc] to execute a simple wasm program. Be sure to also check out the
 [full API documentation][apidoc] for a full listing of what the [`wasmtime`
-crate][crate] has to offer.
+crate][wasmtime] has to offer and the [book examples for
+Rust](./examples-rust-embed.md) for more information.
 
 [apidoc]: https://bytecodealliance.github.io/wasmtime/api/wasmtime/
 [wasmtime]: https://crates.io/crates/wasmtime

docs/embed-rust.md

@@ -0,0 +1,15 @@
+# Debugging
+
+You can also [browse this source code online][code] and clone the wasmtime
+repository to run the example locally.
+
+[code]: https://github.com/bytecodealliance/wasmtime/blob/master/examples/fib-debug/main.c
+
+This example shows off how to set up a module for dynamic runtime debugging via
+a native debugger like GDB or LLDB.
+
+## `main.c`
+
+```c
+{{#include ../examples/fib-debug/main.c}}
+```

docs/examples-c-debugging.md

@@ -0,0 +1,12 @@
+# Embedding in C
+
+This section is intended to showcase the C embedding API for Wasmtime. The C
+embedding API is based on the [proposed wasm C embedding API][proposal] (namely
+[`wasm.h`]) and has a few extension headers (like [`wasi.h`] and
+[`wasmtime.h`]) which are intended to eventually become part of the standard
+themselves one day.
+
+[proposal]: https://github.com/webassembly/wasm-c-api
+[`wasm.h`]: https://github.com/WebAssembly/wasm-c-api/blob/master/include/wasm.h
+[`wasi.h`]: https://github.com/bytecodealliance/wasmtime/blob/master/crates/c-api/include/wasi.h
+[`wasmtime.h`]: https://github.com/bytecodealliance/wasmtime/blob/master/crates/c-api/include/wasmtime.h

docs/examples-c-embed.md

@@ -0,0 +1,22 @@
+# Calculating the GCD
+
+You can also [browse this source code online][code] and clone the wasmtime
+repository to run the example locally.
+
+[code]: https://github.com/bytecodealliance/wasmtime/blob/master/examples/gcd.c
+
+This example shows off how run a wasm program which calculates the GCD of two
+numbers.
+
+## `gcd.wat`
+
+```wat
+{{#include ../examples/gcd.wat}}
+```
+
+
+## `gcd.c`
+
+```c
+{{#include ../examples/gcd.c}}
+```

docs/examples-c-gcd.md

@@ -0,0 +1,22 @@
+# Hello, world!
+
+You can also [browse this source code online][code] and clone the wasmtime
+repository to run the example locally.
+
+[code]: https://github.com/bytecodealliance/wasmtime/blob/master/examples/hello.c
+
+This example shows off how to instantiate a simple wasm module and interact with
+it.
+
+## `hello.wat`
+
+```wat
+{{#include ../examples/hello.wat}}
+```
+
+
+## `hello.c`
+
+```c
+{{#include ../examples/hello.c}}
+```

docs/examples-c-hello-world.md

@@ -0,0 +1,27 @@
+# Linking modules
+
+You can also [browse this source code online][code] and clone the wasmtime
+repository to run the example locally.
+
+[code]: https://github.com/bytecodealliance/wasmtime/blob/master/examples/linking.c
+
+This example shows off how to compile and instantiate modules which link
+together.
+
+## `linking1.wat`
+
+```wat
+{{#include ../examples/linking1.wat}}
+```
+
+## `linking2.wat`
+
+```wat
+{{#include ../examples/linking2.wat}}
+```
+
+## `linking.c`
+
+```c
+{{#include ../examples/linking.c}}
+```