SetjmpLongjmp.md

C setjmp/longjmp support

Build an application

To build an application using setjmp/longjmp, you need two things:

• Enable the necessary LLVM translation (-mllvm -wasm-enable-sjlj)

• Link the setjmp library (-lsetjmp)

Example without LTO

clang -Os -mllvm -wasm-enable-sjlj -o your_app.wasm your_app.c -lsetjmp

Example with LTO

clang -Os -flto=full -mllvm -wasm-enable-sjlj -Wl,-mllvm,-wasm-enable-sjlj -o your_app.wasm your_app.c -lsetjmp

Run an application

To run the application built as in the previous section, you need to use a runtime with exception handling proposal support.

Unfortunately, there are two incompatible versions of exception handling proposal, which is commonly implemented by runtimes.

• The latest version with exnref

• The phase3 version

Example with the latest exception handling proposal

Because the current version of WASI-SDK produces an old version of exception handling proposal instructions, if your runtime implements the latest version of the proposal, you need to convert your module to the latest version.

toywasm is an example of such runtimes.

You can use binaryen wasm-opt command for the conversion.

wasm-opt --translate-to-exnref -all -o your_app.exnref.wasm your_app.wasm

Then you can run it with a runtime supporting the latest version of exception handling proposal.

toywasm --wasi your_app.exnref.wasm

(You may need to enable the support with -D TOYWASM_ENABLE_WASM_EXCEPTION_HANDLING=ON.)

Example with the phase3 exception handling proposal (a bit older version)

If your runtime supports the phase3 version of exception handling proposal, which is the same version as what WASI-SDK currently produces, you can run the produced module as it is.

For example, the classic interpreter of wasm-micro-runtime is one of such runtimes.

iwasm your_app.wasm

(You may need to enable the support with -D WAMR_BUILD_EXCE_HANDLING=1 -D WAMR_BUILD_FAST_INTERP=0.)