DWARF: Fix sequence_end emitting (#2929)

We must emit those, even if otherwise it looks like a line we can
omit, as the ends of sequences have important meaning and
dwarfdump will warn without them.

Looks like fannkuch0 in the test suite already had an example
of an incorrectly-omitted sequence_end, so no need for a new
testcase.

Verified that without this e.g. wasm2.test_exceptions with -g
added will lead to a wasm that warns, but with this PR the debug_line
section is reported as valid by dwarfdump.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/wasm/wasm-debug.cpp b/src/wasm/wasm-debug.cpp
index 8ae7497ed..20c5dfb62 100644
--- a/src/wasm/wasm-debug.cpp
+++ b/src/wasm/wasm-debug.cpp
@@ -241,9 +241,10 @@ struct LineState {
   }
 
   bool needToEmit() {
-    // Zero values imply we can ignore this line.
+    // Zero values imply we can ignore this line, unless it has something
+    // special we must emit.
     // https://github.com/WebAssembly/debugging/issues/9#issuecomment-567720872
-    return line != 0 && addr != 0;
+    return (line != 0 && addr != 0) || endSequence;
   }
 
   // Given an old state, emit the diff from it to this state into a new line