basic structures work in the jit

src/backend/runtime.rs

@@ -3,6 +3,7 @@ use cranelift_codegen::isa::CallConv;
 use cranelift_jit::JITBuilder;
 use cranelift_module::{FuncId, Linkage, Module, ModuleResult};
 use std::collections::HashMap;
+use std::alloc::Layout;
 use std::ffi::CStr;
 use std::fmt::Write;
 use target_lexicon::Triple;
@@ -93,12 +94,17 @@ impl RuntimeFunctions {
     pub fn register_jit_implementations(builder: &mut JITBuilder) {
         let allocation_pointer = unsafe {
             std::alloc::alloc_zeroed(
-                std::alloc::Layout::from_size_align(1024 * 1024, 1024 * 1024)
+                Layout::from_size_align(1024 * 1024, 1024 * 1024)
                     .expect("reasonable layout is reasonable"),
             )
         };
+        let allocation_pointer_pointer = unsafe {
+            let res = std::alloc::alloc(Layout::for_value(&allocation_pointer)) as *mut *mut u8;
+            *res = allocation_pointer;
+            res as *const u8
+        };
         builder.symbol("print", runtime_print as *const u8);
-        builder.symbol("__global_allocation_pointer__", allocation_pointer);
+        builder.symbol("__global_allocation_pointer__", allocation_pointer_pointer);
     }
 }