[wasm2js] Properly handle loops without labels (#7100)

When a loop has no name, the name does not matter, but we also cannot
emit the same name for all such loops, as that is invalid JS. Just do not
emit a while(){} at all in that case, as no continue can exist anyhow.

Fixes #7099

Also fix two missing * in error reporting logic, that was printing pointers
rather than the expression we wanted to print. I think we changed how
iostream prints things years ago, and forgot to update these.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/wasm2js/empty_loop.wast b/test/wasm2js/empty_loop.wast
new file mode 100644
index 000000000..8f22c033d
--- /dev/null
+++ b/test/wasm2js/empty_loop.wast
@@ -0,0 +1,18 @@
+(module
+ (global $g (mut i32) (i32.const 0))
+
+ (func $test (export "test")
+  ;; Loops without labels. We should not emit anything invalid here (like a
+  ;; null name, which would end up identical between the two, which is wrong).
+  (loop
+   (loop
+    ;; Some content, so the loop is not trivial.
+    (global.set $g
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+   (unreachable)
+  )
+ )
+)