From ff503008ea3540963d9e06b57051cf9bdc5fa1f9 Mon Sep 17 00:00:00 2001
From: Richard Feldman <oss@rtfeldman.com>
Date: Sun, 9 Nov 2025 21:05:14 -0500
Subject: [PATCH] Update some comments

---
 src/interpreter_shim/main.zig | 12 +++++++-----
 test/fx/platform/host.zig     | 12 +++++++-----
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/interpreter_shim/main.zig b/src/interpreter_shim/main.zig
index 79f57be062..39a52bb206 100644
--- a/src/interpreter_shim/main.zig
+++ b/src/interpreter_shim/main.zig
@@ -76,9 +76,10 @@ const ShimError = error{
 /// Expected format in shared memory: [u64 parent_address][u32 entry_count][ModuleEnv data][u32[] def_indices]
 export fn roc_entrypoint(entry_idx: u32, ops: *builtins.host_abi.RocOps, ret_ptr: *anyopaque, arg_ptr: ?*anyopaque) callconv(.c) void {
     evaluateFromSharedMemory(entry_idx, ops, ret_ptr, arg_ptr) catch |err| {
-        var buf: [512]u8 = undefined;
-        const msg2 = std.fmt.bufPrint(&buf, "Error evaluating from shared memory: {s} (entry_idx={})", .{ @errorName(err), entry_idx }) catch "Error evaluating from shared memory";
+        // Use heap allocation for error message to avoid fixed buffer size limits
+        const msg2 = std.fmt.allocPrint(std.heap.page_allocator, "Error evaluating from shared memory: {s} (entry_idx={})", .{ @errorName(err), entry_idx }) catch "Error evaluating from shared memory";
         ops.crash(msg2);
+        // Note: We're about to crash, so it's ok to leak this allocation
     };
 }
 
@@ -99,15 +100,16 @@ fn initializeSharedMemoryOnce(roc_ops: *RocOps) ShimError!void {
     }
 
     const allocator = std.heap.page_allocator;
-    var buf: [256]u8 = undefined;
 
     // Get page size
     const page_size = SharedMemoryAllocator.getSystemPageSize() catch 4096;
 
     // Create shared memory allocator from coordination info
     var shm = SharedMemoryAllocator.fromCoordination(allocator, page_size) catch |err| {
-        const msg2 = std.fmt.bufPrint(&buf, "Failed to create shared memory allocator: {s}", .{@errorName(err)}) catch "Failed to create shared memory allocator";
+        // Use heap allocation for error message to avoid fixed buffer size limits
+        const msg2 = std.fmt.allocPrint(allocator, "Failed to create shared memory allocator: {s}", .{@errorName(err)}) catch "Failed to create shared memory allocator";
         roc_ops.crash(msg2);
+        // Note: We're about to crash, so it's ok to leak this allocation
         return error.SharedMemoryError;
     };
 
@@ -231,7 +233,7 @@ fn setupModuleEnv(shm: *SharedMemoryAllocator, roc_ops: *RocOps) ShimError!*Modu
         } else "";
 
         // Deserialize the ModuleEnv with the relocated module_name
-        // Empty string is used for source since it's not needed in the interpreter
+        // Source text is not available because we don't put it in the shared memory.
         module_envs[i] = try serialized_ptr.deserialize(offset, std.heap.page_allocator, "", module_name);
     }
 
diff --git a/test/fx/platform/host.zig b/test/fx/platform/host.zig
index d18653525d..94699b46de 100644
--- a/test/fx/platform/host.zig
+++ b/test/fx/platform/host.zig
@@ -190,10 +190,12 @@ fn platform_main() !void {
     };
 
     // Call the app's main! entrypoint
-    var unit_result: [0]u8 = undefined; // Result is {} which is zero-sized
-    // For a function with signature () => {}, the argument is an empty tuple (zero parameters)
-    // An empty tuple is zero-sized, so we pass a zero-sized value
-    // Note: Can't pass null here - Roc-generated code dereferences the pointer even for zero-sized types
+    var ret: [0]u8 = undefined; // Result is {} which is zero-sized
     var args: [0]u8 = undefined;
-    roc__main_for_host(&roc_ops, @as(*anyopaque, @ptrCast(&unit_result)), @as(*anyopaque, @ptrCast(&args)));
+    // Note: although this is a function with no args and a zero-sized return value,
+    // we can't currently pass null pointers for either of these because Roc will
+    // currently dereference both of these eagerly even though it won't use either,
+    // causing a segfault if you pass null. This should be changed! Dereferencing
+    // garbage memory is obviously pointless, and there's no reason we should do it.
+    roc__main_for_host(&roc_ops, @as(*anyopaque, @ptrCast(&ret)), @as(*anyopaque, @ptrCast(&args)));
 }