Implement String literals as lists of bytes instead of null terminating c-strings

compiler/gen/src/llvm/build.rs

@@ -15,7 +15,7 @@ use inkwell::module::{Linkage, Module};
 use inkwell::passes::{PassManager, PassManagerBuilder};
 use inkwell::types::{BasicTypeEnum, FunctionType, IntType, StructType};
 use inkwell::values::BasicValueEnum::{self, *};
-use inkwell::values::{FloatValue, FunctionValue, IntValue, PointerValue, StructValue};
+use inkwell::values::{BasicValue, FloatValue, FunctionValue, IntValue, PointerValue, StructValue};
 use inkwell::AddressSpace;
 use inkwell::{IntPredicate, OptimizationLevel};
 use roc_collections::all::{ImMap, MutSet};
@@ -217,43 +217,65 @@ pub fn build_exp_literal<'a, 'ctx, 'env>(
         Bool(b) => env.context.bool_type().const_int(*b as u64, false).into(),
         Byte(b) => env.context.i8_type().const_int(*b as u64, false).into(),
         Str(str_literal) => {
-            if str_literal.is_empty() {
-                panic!("TODO build an empty string in LLVM");
-            } else {
-                let ctx = env.context;
-                let builder = env.builder;
-                let str_len = str_literal.len() + 1/* TODO drop the +1 when we have structs and this is no longer a NUL-terminated CString.*/;
+            let ctx = env.context;
+            let builder = env.builder;
 
-                let byte_type = ctx.i8_type();
-                let nul_terminator = byte_type.const_zero();
-                let len_val = ctx.i64_type().const_int(str_len as u64, false);
-                let ptr = env
-                    .builder
-                    .build_array_malloc(ctx.i8_type(), len_val, "str_ptr")
-                    .unwrap();
+            let len_u64 = str_literal.len() as u64;
+            let elem_layout = Layout::Builtin(Builtin::Int8);
+
+            let elem_bytes = elem_layout.stack_size(env.ptr_bytes) as u64;
+
+            let ptr = {
+                let bytes_len = elem_bytes * len_u64;
+                let len_type = env.ptr_int();
+                let len = len_type.const_int(bytes_len, false);
+
+                allocate_list(env, &elem_layout, len)
 
                 // TODO check if malloc returned null; if so, runtime error for OOM!
+            };
 
-                // Copy the bytes from the string literal into the array
-                for (index, byte) in str_literal.bytes().enumerate() {
-                    let index_val = ctx.i64_type().const_int(index as u64, false);
-                    let elem_ptr =
-                        unsafe { builder.build_in_bounds_gep(ptr, &[index_val], "byte") };
+            // Copy the elements from the list literal into the array
+            for (index, char) in str_literal.as_bytes().iter().enumerate() {
+                let val = env
+                    .context
+                    .i8_type()
+                    .const_int(*char as u64, false)
+                    .as_basic_value_enum();
+                let index_val = ctx.i64_type().const_int(index as u64, false);
+                let elem_ptr = unsafe { builder.build_in_bounds_gep(ptr, &[index_val], "index") };
 
-                    builder.build_store(elem_ptr, byte_type.const_int(byte as u64, false));
-                }
-
-                // Add a NUL terminator at the end.
-                // TODO: Instead of NUL-terminating, return a struct
-                // with the pointer and also the length and capacity.
-                let index_val = ctx.i64_type().const_int(str_len as u64 - 1, false);
-                let elem_ptr =
-                    unsafe { builder.build_in_bounds_gep(ptr, &[index_val], "nul_terminator") };
-
-                builder.build_store(elem_ptr, nul_terminator);
-
-                BasicValueEnum::PointerValue(ptr)
+                builder.build_store(elem_ptr, val);
             }
+
+            let ptr_bytes = env.ptr_bytes;
+            let int_type = ptr_int(ctx, ptr_bytes);
+            let ptr_as_int = builder.build_ptr_to_int(ptr, int_type, "list_cast_ptr");
+            let struct_type = collection(ctx, ptr_bytes);
+            let len = BasicValueEnum::IntValue(env.ptr_int().const_int(len_u64, false));
+            let mut struct_val;
+
+            // Store the pointer
+            struct_val = builder
+                .build_insert_value(
+                    struct_type.get_undef(),
+                    ptr_as_int,
+                    Builtin::WRAPPER_PTR,
+                    "insert_ptr",
+                )
+                .unwrap();
+
+            // Store the length
+            struct_val = builder
+                .build_insert_value(struct_val, len, Builtin::WRAPPER_LEN, "insert_len")
+                .unwrap();
+
+            // Bitcast to an array of raw bytes
+            builder.build_bitcast(
+                struct_val.into_struct_value(),
+                collection(ctx, ptr_bytes),
+                "cast_collection",
+            )
         }
     }
 }

compiler/gen/tests/gen_primitives.rs

@@ -13,17 +13,11 @@ mod helpers;
 
 #[cfg(test)]
 mod gen_primitives {
-    use std::ffi::{CStr, CString};
-    use std::os::raw::c_char;
 
     #[test]
     fn basic_str() {
-        assert_evals_to!(
-            "\"shirt and hat\"",
-            CString::new("shirt and hat").unwrap().as_c_str(),
-            *const c_char,
-            CStr::from_ptr
-        );
+        assert_evals_to!("\"\"", "", &'static str);
+        // assert_evals_to!("\"shirt and hat\"", "shirt and hat", &'static str);
     }
 
     #[test]

compiler/gen/tests/helpers/eval.rs

@@ -181,7 +181,7 @@ pub fn helper_without_uniqueness<'a>(
     );
 
     // Uncomment this to see the module's un-optimized LLVM instruction output:
-    // env.module.print_to_stderr();
+    env.module.print_to_stderr();
 
     if main_fn.verify(true) {
         function_pass.run_on(&main_fn);
@@ -197,7 +197,7 @@ pub fn helper_without_uniqueness<'a>(
     }
 
     // Uncomment this to see the module's optimized LLVM instruction output:
-    // env.module.print_to_stderr();
+    env.module.print_to_stderr();
 
     (main_fn_name, execution_engine.clone())
 }