[grawprog]

The way I ended up structuring my opcodes was similar to your way but a little different still. I ended up using function pointers but an array of them. Each opcode is defined in an enum and will be assigned to each funtion pointer based on it's corresponding array index. When the virtual CPU reads an opcode it just calls the function pointed to by the pointer at that index.

I found doing it this way makes it easy to change or add opcodes without needing to go back through a giant switch statement to find and rearrange everything. As a bonus too, the assembler just uses the same enum and basically just works through it the opposite way the CPU does. Translating keywords to the matching opcode index in the array then writing the index to the correct memory address in the binary. This also means any time I update an opcode or add one in the virtual machine all I have to do is add it to the enum and both the assembler and virtual machine will be updated without having to do anything else.

[sifoobar]

Nice to hear! That's what I try to tell people who are asking for the right type theory book or the right dispatch method or whatever before even having a look. It's the same old problem solving; and here are always multiple solutions, each with it's own set of compromises. Claiming the one true way of doing anything related to software is delusional. We're barely scratching the surface.

Edit: While we're here; may I ask how you break out of the dispatch loop? Do you test an end-condition on each iteration? If that's the case, the longjmp trick might be worth trying. The condition will mostly be false, so it might make sense to pay more when it happens instead. You may find the essence of it in sgl_run at the bottom of sgl.c [0].

[0] https://gitlab.com/sifoo/snigl/blob/master/src/snigl/sgl.c#L...

[vardump]

> Edit: While we're here; may I ask how you break out of the dispatch loop? Do you test an end-condition on each iteration? ...

For what it is worth my JITter uses mprotect from other thread to change page permissions to generate an exception to break out of JITted code. Same would work for dispatcher as well.

The advantage is it's completely free performance wise while the code is running. The need for signal handler is less awesome.