Fix crash on accessing function parameters

[sampsyo]

We're currently hitting a segfault when trying to iterate over the arguments of a newly-constructed function. Here's a piece of the traceback, from LLDB:

 * frame #0: 0x0000000106116f88 libLLVM.dylib`llvm::LLVMContext::shouldDiscardValueNames() const + 4
   frame #1: 0x0000000106145b77 libLLVM.dylib`llvm::Value::setNameImpl(llvm::Twine const&) + 39
   frame #2: 0x0000000106145e0c libLLVM.dylib`llvm::Value::setName(llvm::Twine const&) + 14
   frame #3: 0x00000001060f5f7a libLLVM.dylib`llvm::Argument::Argument(llvm::Type*, llvm::Twine const&, llvm::Function*) + 110
   frame #4: 0x00000001060f702b libLLVM.dylib`llvm::Function::BuildLazyArguments() const + 105
   frame #5: 0x00000001060d9dd1 libLLVM.dylib`LLVMGetParam + 27

[sampsyo]

Hey @rhenwood39—in the above commit, I tried exploring your hypothesis that constructing the argument types for LLVMFunctionType was going wrong. I tried switching to ref-array to make sure we were constructing the array of pointers correctly, to no avail. 😢

[sampsyo]

Wait a second! I actually had just not waited long enough for my tsc --watch to catch up. It works, for me at least!

Ready> def f(a b) a+b
Program: def f(a b) a+b

Read function definition:
; ModuleID = 'calculator_module'
source_filename = "calculator_module"

define float @f(float %a, float %b) {
entry:
  %addtmp = fadd float %a, %b
  ret float %addtmp
}



Ready>

🎉

[rhenwood39]

Awesome!

[rhenwood39]

It looks like it still complains when you actually try to call a function though. I'll take a look at that later.

[sampsyo]

I suppose that makes sense—in this buildCall method here:

node-llvmc/src/wrapped.ts

Lines 100 to 102 in 0367634

	buildCall(func: Function, args: Value[], name: string): Value {
	return new Value(LLVM.LLVMBuildCall(func, args, args.length, name));
	}

we'll need to use the same trick to build up a C array of pointers from the JavaScript array of objects. Maybe this stanza:

node-llvmc/src/wrapped.ts

Lines 240 to 246 in 0367634

	// Construct an array containing the parameter references.
	let paramtypes = new PointerArray(params.length);
	let i = 0;
	for (let param of params) {
	paramtypes[i] = param.ref;
	++i;
	}

should be put into a helper function and reused there?

[rhenwood39]

Got it working :)

I think we are going to have to go through llvm.ts eventually and convert the voidpp's, etc. to PointerArrays where appropriate. I think we have an issue open regarding that, so I'll make a follow-up note there.