compiler: a test program may hold a phase handler - the test runner called @rt_init whenever the program had systems, and a handler alone makes none (LLVM: use of undefined value '@rt_init'); it calls it only when it exists, as an entry program's main does; a ludic test case with a handler (added, not run); reseeded, bootstrap-cfree fixpoint holds

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changes/test-handler-rt-init.md

@@ -0,0 +1,6 @@
+bump: patch
+type: fix
+**A test program may hold a phase handler.** A program with `test` blocks and a `handler ... phase`
+(its own, or one a module it imports declares) failed to compile with LLVM's "use of undefined value
+'@rt_init'": the test runner called the runtime's `rt_init` whenever the program had systems, and a
+handler alone makes none. It now calls it only when it exists, as an `entry` program's `main` does.

selfhost/backend/emit_decl.ludic

@@ -161,7 +161,7 @@ function emit_test_runner() -> void {
   emit(`{lrun0}:\n`)
   emit("  call void @L_init_runtime()\n")
   if has_ecs() { emit("  call void @L_grow(i32 1)\n") }
-  if has_ecs() { emit("  call void @rt_init()\n") }
+  if (find_fn("rt_init") != null) { emit("  call void " + fn_sym("rt_init") + "()\n") }   # as emit_main: a handler alone makes no rt_init
   emit("  call void @L_init_globals()\n")
   i = 0
   while i < len(g_tests) {

tools/ludic-cli/test.ludic

@@ -786,6 +786,11 @@ function test_dir_case() -> void {
   if not shq(`cd {work} && {root}/bin/ludic test pk/tests -j 2 > out3.txt 2>&1`) { bad2(lbl2, capture(`cat {work}/out3.txt`));  return }
   if not shq(`grep -q 'pk/tests/scratch.ludic  (2 tests)' {work}/out3.txt`) { bad2(lbl2, capture(`cat {work}/out3.txt`));  return }
   ok(lbl2)
+  # a test program holding a phase handler: the runner boots no frame loop and calls no rt_init it lacks
+  let lbl3 = "ludic test: a program with a phase handler compiles and runs its tests"
+  write_file(`{work}/pk/tests/handler.ludic`, "program D {\n  handler K phase Input { }\n  test \"d\" {\n    expect_eq(1, 1)\n  }\n}\n")
+  if not shq(`cd {work} && {root}/bin/ludic test pk/tests/handler.ludic > out4.txt 2>&1`) { bad2(lbl3, capture(`cat {work}/out4.txt`));  return }
+  ok(lbl3)
 }
 
 # package.ludic drives the CLI: `entry` (or the one program under src/) is what