wasi | quick intro to WASI | Learning library

When you want to create a linked list, you should use a struct Cell that contains two types of date: the first is your data itself (Contact in your case) the other is a pointer to the next cell in the list (next). Using this type of implementation you make your code more readable, modular and reusable.

Couple of problems:

1. The major problem is that there are two Contact *new = malloc(sizeof(Contact)); lines. One inside the loop and one outside. They are two different variables. The while loop condition is using the one outside the loop. Hence the fscanf is writing to the same memory for every loop. One way to fix that is to make the second instance just new = malloc(sizeof(Contact));. Note that this loop has a memory leak as the last allocated node is lost - left to you as an exercise to fix.

2. searching_contact has an infinete loop as the if (strcmp(name, cursor->name) == 0) block is missing a break.

Yes it is implemented in all runtimes implementing wasi. The reason is that this feature is related to import/export mechanism of WebAssembly.

As a rule, a WHERE clause of SELECT .. FOR XML .. shoud make the subquery depend on exactly the same columns which are listed in the GROUP BY clause of the outer query. Try

This is answered in The wasm-bindgen Guide: Using console.log:

• Method #1, binding it manually:

Emscripten itself does not aim to provide any sandboxing. With emscripten, any sandboxing of the compiled code is provide by the host environment. For example, by far the most common host if the web which has a very strong sandbox of its own. If you run emscripten code on the web is has exactly the same privileges as the rest of the JS code on the page. Likewise, if you run emscripten generated code under node if has the same privileges as the rest of the JS code in the process (i.e. by default this means the same privileges as the node process itself).

One of the goals of WASI however is to define a strict sandbox such that it becomes simple for a host environment to decide exactly what resources to share with a WebAssembly module.

Currently in Rust we can really only create WASI binaries, not libraries. WASI only works for the duration of a main function that needs to be there. Calling the wasi functions from anywhere else segfaults because libpreopen isn't initialized.

So to summarize, how to fix this currently:

• Do not have lib.crate-type at all
• Have the file be src/main.rs, not src/lib.rs
• Have #![no_main] at the top of the src/main.rs
• Use RUSTFLAGS="-Z wasi-exec-model=reactor" cargo +nightly build --target wasm32-wasi
• Make sure that you call _initialize before anything else

https://github.com/WebAssembly/WASI/issues/24

https://github.com/rust-lang/rust/pull/79997

In my case:

wasi_fs_example/src/main.rs:

The problem is the difference between initialization and assignment. Initialization is basically an assignment done together with declaration.

When you want to assign a compound literal (for example {"Kevin Mahendra", 22, "Male"}) you need to cast it by putting (student) in front of it, but the cast is not necessary during initialization.

Note: Technically, it's not a cast. But it does look exactly like a cast, and many are calling it casting, either because of lack of knowledge or just because of sloppy language. I thought it was a cast before Eric Postpischil pointed it out.

Change to

You can trigger the export of a given symbol by setting the wasm-export-name and wasm-export-name attributes.

In C/C++ these correspond the export_name and export_module clang attribtes.

See llvm/test/CodeGen/WebAssembly/export-name.ll in the llvm tree for an example of this.

You can also ask the linker to export a given symbol with the --export command line flag. See https://lld.llvm.org/WebAssembly.html#exports.