WebAssembly/Threads

Thread support

This page contains some collected informations on the features needed for thread support in WebAssembly (in the browser).

Thread support consists of 2 parts:

• Atomic instructions.
• Actually starting a thread.

Atomic instructions

The proposed specs 

When the Free Pascal RTL is compiled with -dFPC_WASM_THREADS, the following RTL functions will use the new atomic instructions and thus should be thread safe in a multithreaded environment:

InterlockedDecrement
InterlockedIncrement
InterlockedExchange
InterlockedCompareExchange
InterlockedExchangeAdd

Note that these require proper alignment (4 bytes) of the target, otherwise they trap (i.e. terminate the program with a stack trace).

Thread support

Webassembly relies on the hosting environment to actually start threads.

Some extra info:

• something like specs
• A demo
• related