From a4ccef622cad5c1cdcbce75be20816714a419fc3 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 15 Jan 2026 15:44:22 -0800
Subject: [PATCH 01/11] start

---
 src/tools/wasm-as.cpp                  | 26 ++++++++++++++++----------
 src/tools/wasm-ctor-eval.cpp           |  2 ++
 src/tools/wasm-dis.cpp                 | 10 ++++++++--
 src/tools/wasm-emscripten-finalize.cpp |  3 ++-
 src/tools/wasm-merge.cpp               |  2 ++
 src/tools/wasm-metadce.cpp             |  2 ++
 src/tools/wasm-opt.cpp                 |  3 +++
 src/tools/wasm-shell.cpp               |  2 ++
 src/tools/wasm2js.cpp                  | 16 +++++++++++-----
 9 files changed, 48 insertions(+), 18 deletions(-)

diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index 8d0dbd6495b..36acd6eacea 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -131,19 +131,25 @@ int main(int argc, const char* argv[]) {
   if (options.debug) {
     std::cerr << "writing..." << std::endl;
   }
-  ModuleWriter writer(options.passOptions);
-  writer.setBinary(true);
-  writer.setDebugInfo(debugInfo);
-  if (sourceMapFilename.size()) {
-    writer.setSourceMapFilename(sourceMapFilename);
-    writer.setSourceMapUrl(sourceMapUrl);
-  }
-  if (symbolMap.size() > 0) {
-    writer.setSymbolMap(symbolMap);
+
+  // Ensure the destructor of ModuleWriter runs before quick_exit.
+  {
+    ModuleWriter writer(options.passOptions);
+    writer.setBinary(true);
+    writer.setDebugInfo(debugInfo);
+    if (sourceMapFilename.size()) {
+      writer.setSourceMapFilename(sourceMapFilename);
+      writer.setSourceMapUrl(sourceMapUrl);
+    }
+    if (symbolMap.size() > 0) {
+      writer.setSymbolMap(symbolMap);
+    }
+    writer.write(wasm, options.extra["output"]);
   }
-  writer.write(wasm, options.extra["output"]);
 
   if (options.debug) {
     std::cerr << "Done." << std::endl;
   }
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm-ctor-eval.cpp b/src/tools/wasm-ctor-eval.cpp
index 1407682faf9..24b67acb4de 100644
--- a/src/tools/wasm-ctor-eval.cpp
+++ b/src/tools/wasm-ctor-eval.cpp
@@ -1618,4 +1618,6 @@ int main(int argc, const char* argv[]) {
     writer.setDebugInfo(debugInfo);
     writer.write(wasm, options.extra["output"]);
   }
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm-dis.cpp b/src/tools/wasm-dis.cpp
index be3e7bd10d9..89ec560ce73 100644
--- a/src/tools/wasm-dis.cpp
+++ b/src/tools/wasm-dis.cpp
@@ -98,10 +98,16 @@ int main(int argc, const char* argv[]) {
   if (options.debug) {
     std::cerr << "Printing..." << std::endl;
   }
-  Output output(options.extra["output"], Flags::Text);
-  output.getStream() << wasm << '\n';
+
+  // Ensure the destructor of Output runs before quick_exit.
+  {
+    Output output(options.extra["output"], Flags::Text);
+    output.getStream() << wasm << '\n';
+  }
 
   if (options.debug) {
     std::cerr << "Done." << std::endl;
   }
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index 53e3be196dc..b7e3e11fc72 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -289,5 +289,6 @@ int main(int argc, const char* argv[]) {
     }
     writer.write(wasm, output);
   }
-  return 0;
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm-merge.cpp b/src/tools/wasm-merge.cpp
index d9a991a58cc..39a97fb0efe 100644
--- a/src/tools/wasm-merge.cpp
+++ b/src/tools/wasm-merge.cpp
@@ -832,4 +832,6 @@ Input source maps can be specified by adding an -ism option right after the modu
     }
     writer.write(merged, options.extra["output"]);
   }
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm-metadce.cpp b/src/tools/wasm-metadce.cpp
index b677e575abf..66d99ec6e8a 100644
--- a/src/tools/wasm-metadce.cpp
+++ b/src/tools/wasm-metadce.cpp
@@ -674,4 +674,6 @@ int main(int argc, const char* argv[]) {
 
   // Clean up
   free(copy);
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index 310544c9451..cc2772c4564 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -496,5 +496,8 @@ For more on how to optimize effectively, see
       Fatal() << "extra fuzz command output differs\n";
     }
   }
+
+  std::quick_exit(0);
+
   return 0;
 }
diff --git a/src/tools/wasm-shell.cpp b/src/tools/wasm-shell.cpp
index 046bb33cecd..b8a02fb0dcc 100644
--- a/src/tools/wasm-shell.cpp
+++ b/src/tools/wasm-shell.cpp
@@ -603,4 +603,6 @@ int main(int argc, const char* argv[]) {
   Colors::bold(std::cerr);
   std::cerr << "all checks passed.\n";
   Colors::normal(std::cerr);
+
+  std::quick_exit(0);
 }
diff --git a/src/tools/wasm2js.cpp b/src/tools/wasm2js.cpp
index c6277c6c30f..2515905e18e 100644
--- a/src/tools/wasm2js.cpp
+++ b/src/tools/wasm2js.cpp
@@ -993,14 +993,20 @@ int main(int argc, const char* argv[]) {
   if (options.debug) {
     std::cerr << "j-printing..." << std::endl;
   }
-  Output output(options.extra["output"], Flags::Text);
-  if (script && options.extra["asserts"] == "1") {
-    AssertionEmitter(*script, output, flags, options).emit();
-  } else {
-    emitWasm(*wasm, output, flags, options.passOptions, "asmFunc");
+
+  // Ensure the destructor of Output runs before quick_exit.
+  {
+    Output output(options.extra["output"], Flags::Text);
+    if (script && options.extra["asserts"] == "1") {
+      AssertionEmitter(*script, output, flags, options).emit();
+    } else {
+      emitWasm(*wasm, output, flags, options.passOptions, "asmFunc");
+    }
   }
 
   if (options.debug) {
     std::cerr << "done." << std::endl;
   }
+
+  std::quick_exit(0);
 }

From 1728cd79c2f824bd466f69a812333a1c515500c8 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 15 Jan 2026 15:49:56 -0800
Subject: [PATCH 02/11] nice

---
 src/support/file.cpp                   | 7 +++++++
 src/support/file.h                     | 8 +++++++-
 src/tools/wasm-as.cpp                  | 2 +-
 src/tools/wasm-ctor-eval.cpp           | 2 +-
 src/tools/wasm-dis.cpp                 | 2 +-
 src/tools/wasm-emscripten-finalize.cpp | 2 +-
 src/tools/wasm-merge.cpp               | 2 +-
 src/tools/wasm-metadce.cpp             | 2 +-
 src/tools/wasm-opt.cpp                 | 4 +---
 src/tools/wasm-shell.cpp               | 2 +-
 src/tools/wasm2js.cpp                  | 2 +-
 11 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/support/file.cpp b/src/support/file.cpp
index 08b9e31af91..c43b4be10d7 100644
--- a/src/support/file.cpp
+++ b/src/support/file.cpp
@@ -135,3 +135,10 @@ size_t wasm::file_size(std::string filename) {
                        std::ifstream::ate | std::ifstream::binary);
   return infile.tellg();
 }
+
+void flush_and_quick_exit() {
+  std::cout << std::flush;
+  std::cerr << std::flush;
+  std::quick_exit(0);
+}
+
diff --git a/src/support/file.h b/src/support/file.h
index ae91831c98f..f81de9f6444 100644
--- a/src/support/file.h
+++ b/src/support/file.h
@@ -72,9 +72,15 @@ class Output {
 // Copies a file to another file
 void copy_file(std::string input, std::string output);
 
-// Retusn the size of a file
+// Return the size of a file
 size_t file_size(std::string filename);
 
+// Flush stdout and stderr, and quickly exit. This assumes that all files that
+// need flushing have been flushed, that is, no global ctors or RAII in main's
+// top level are depended on (using quick_exit then avoids running global dtors,
+// which saves otherwise wasted time).
+void flush_and_quick_exit();
+
 } // namespace wasm
 
 #endif // wasm_support_file_h
diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index 36acd6eacea..3db086c1a55 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -151,5 +151,5 @@ int main(int argc, const char* argv[]) {
     std::cerr << "Done." << std::endl;
   }
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-ctor-eval.cpp b/src/tools/wasm-ctor-eval.cpp
index 24b67acb4de..2d8dda63ee1 100644
--- a/src/tools/wasm-ctor-eval.cpp
+++ b/src/tools/wasm-ctor-eval.cpp
@@ -1619,5 +1619,5 @@ int main(int argc, const char* argv[]) {
     writer.write(wasm, options.extra["output"]);
   }
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-dis.cpp b/src/tools/wasm-dis.cpp
index 89ec560ce73..bcd7241743b 100644
--- a/src/tools/wasm-dis.cpp
+++ b/src/tools/wasm-dis.cpp
@@ -109,5 +109,5 @@ int main(int argc, const char* argv[]) {
     std::cerr << "Done." << std::endl;
   }
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index b7e3e11fc72..303664d88d5 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -290,5 +290,5 @@ int main(int argc, const char* argv[]) {
     writer.write(wasm, output);
   }
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-merge.cpp b/src/tools/wasm-merge.cpp
index 39a97fb0efe..d44115399f2 100644
--- a/src/tools/wasm-merge.cpp
+++ b/src/tools/wasm-merge.cpp
@@ -833,5 +833,5 @@ Input source maps can be specified by adding an -ism option right after the modu
     writer.write(merged, options.extra["output"]);
   }
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-metadce.cpp b/src/tools/wasm-metadce.cpp
index 66d99ec6e8a..e12209b4d17 100644
--- a/src/tools/wasm-metadce.cpp
+++ b/src/tools/wasm-metadce.cpp
@@ -675,5 +675,5 @@ int main(int argc, const char* argv[]) {
   // Clean up
   free(copy);
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index cc2772c4564..a788478be4a 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -497,7 +497,5 @@ For more on how to optimize effectively, see
     }
   }
 
-  std::quick_exit(0);
-
-  return 0;
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm-shell.cpp b/src/tools/wasm-shell.cpp
index b8a02fb0dcc..8ec13026ace 100644
--- a/src/tools/wasm-shell.cpp
+++ b/src/tools/wasm-shell.cpp
@@ -604,5 +604,5 @@ int main(int argc, const char* argv[]) {
   std::cerr << "all checks passed.\n";
   Colors::normal(std::cerr);
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }
diff --git a/src/tools/wasm2js.cpp b/src/tools/wasm2js.cpp
index 2515905e18e..e7da05df890 100644
--- a/src/tools/wasm2js.cpp
+++ b/src/tools/wasm2js.cpp
@@ -1008,5 +1008,5 @@ int main(int argc, const char* argv[]) {
     std::cerr << "done." << std::endl;
   }
 
-  std::quick_exit(0);
+  flush_and_quick_exit();
 }

From a6dc74ddc18d4da3031f0f101016d92b720a6d67 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 15 Jan 2026 15:52:15 -0800
Subject: [PATCH 03/11] opos

---
 src/support/file.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/support/file.cpp b/src/support/file.cpp
index c43b4be10d7..6760bf2bb45 100644
--- a/src/support/file.cpp
+++ b/src/support/file.cpp
@@ -136,7 +136,7 @@ size_t wasm::file_size(std::string filename) {
   return infile.tellg();
 }
 
-void flush_and_quick_exit() {
+void wasm::flush_and_quick_exit() {
   std::cout << std::flush;
   std::cerr << std::flush;
   std::quick_exit(0);

From c6732cb5acd90c386317541a2ce6f5124607b2f4 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 15 Jan 2026 15:52:24 -0800
Subject: [PATCH 04/11] fmt

---
 src/support/file.cpp | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/support/file.cpp b/src/support/file.cpp
index 6760bf2bb45..931f9328355 100644
--- a/src/support/file.cpp
+++ b/src/support/file.cpp
@@ -141,4 +141,3 @@ void wasm::flush_and_quick_exit() {
   std::cerr << std::flush;
   std::quick_exit(0);
 }
-

From 2a9e76b4f1b296da0d2bdf6b0a6ea0c301dbd018 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 15 Jan 2026 16:37:33 -0800
Subject: [PATCH 05/11] fix

---
 src/tools/wasm-opt.cpp | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index a788478be4a..8736f6f0627 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -476,18 +476,23 @@ For more on how to optimize effectively, see
         std::cerr << "warning: no output file specified, not emitting output\n";
       }
     }
+
+    flush_and_quick_exit();
     return 0;
   }
 
-  BYN_TRACE("writing...\n");
-  ModuleWriter writer(options.passOptions);
-  writer.setBinary(emitBinary);
-  writer.setDebugInfo(options.passOptions.debugInfo);
-  if (outputSourceMapFilename.size()) {
-    writer.setSourceMapFilename(outputSourceMapFilename);
-    writer.setSourceMapUrl(outputSourceMapUrl);
+  // Ensure the destructor of ModuleWriter runs before quick_exit.
+  {
+    BYN_TRACE("writing...\n");
+    ModuleWriter writer(options.passOptions);
+    writer.setBinary(emitBinary);
+    writer.setDebugInfo(options.passOptions.debugInfo);
+    if (outputSourceMapFilename.size()) {
+      writer.setSourceMapFilename(outputSourceMapFilename);
+      writer.setSourceMapUrl(outputSourceMapUrl);
+    }
+    writer.write(wasm, options.extra["output"]);
   }
-  writer.write(wasm, options.extra["output"]);
 
   if (extraFuzzCommand.size() > 0) {
     auto secondOutput = runCommand(extraFuzzCommand);

From 4b73e3551c0108560d2df09adcbc82aab98dc4a4 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 16 Jan 2026 08:04:55 -0800
Subject: [PATCH 06/11] [[noreturn]]

---
 src/support/file.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/support/file.h b/src/support/file.h
index f81de9f6444..6dc108db82c 100644
--- a/src/support/file.h
+++ b/src/support/file.h
@@ -79,7 +79,7 @@ size_t file_size(std::string filename);
 // need flushing have been flushed, that is, no global ctors or RAII in main's
 // top level are depended on (using quick_exit then avoids running global dtors,
 // which saves otherwise wasted time).
-void flush_and_quick_exit();
+[[noreturn]] void flush_and_quick_exit();
 
 } // namespace wasm
 

From 8afe5b17f1a9bdb5057134fbbbfe0ffeab156341 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 16 Jan 2026 11:04:57 -0800
Subject: [PATCH 07/11] explicit 0

---
 src/support/file.cpp                   | 4 ++--
 src/support/file.h                     | 2 +-
 src/tools/wasm-as.cpp                  | 2 +-
 src/tools/wasm-ctor-eval.cpp           | 2 +-
 src/tools/wasm-dis.cpp                 | 2 +-
 src/tools/wasm-emscripten-finalize.cpp | 2 +-
 src/tools/wasm-merge.cpp               | 2 +-
 src/tools/wasm-metadce.cpp             | 2 +-
 src/tools/wasm-opt.cpp                 | 4 ++--
 src/tools/wasm-shell.cpp               | 2 +-
 src/tools/wasm2js.cpp                  | 2 +-
 11 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/support/file.cpp b/src/support/file.cpp
index 931f9328355..dbb44afd643 100644
--- a/src/support/file.cpp
+++ b/src/support/file.cpp
@@ -136,8 +136,8 @@ size_t wasm::file_size(std::string filename) {
   return infile.tellg();
 }
 
-void wasm::flush_and_quick_exit() {
+void wasm::flush_and_quick_exit(int code) {
   std::cout << std::flush;
   std::cerr << std::flush;
-  std::quick_exit(0);
+  std::quick_exit(code);
 }
diff --git a/src/support/file.h b/src/support/file.h
index 6dc108db82c..0726417285f 100644
--- a/src/support/file.h
+++ b/src/support/file.h
@@ -79,7 +79,7 @@ size_t file_size(std::string filename);
 // need flushing have been flushed, that is, no global ctors or RAII in main's
 // top level are depended on (using quick_exit then avoids running global dtors,
 // which saves otherwise wasted time).
-[[noreturn]] void flush_and_quick_exit();
+[[noreturn]] void flush_and_quick_exit(int code);
 
 } // namespace wasm
 
diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index 3db086c1a55..3eabdef3120 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -151,5 +151,5 @@ int main(int argc, const char* argv[]) {
     std::cerr << "Done." << std::endl;
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-ctor-eval.cpp b/src/tools/wasm-ctor-eval.cpp
index 2d8dda63ee1..fae516d8f6a 100644
--- a/src/tools/wasm-ctor-eval.cpp
+++ b/src/tools/wasm-ctor-eval.cpp
@@ -1619,5 +1619,5 @@ int main(int argc, const char* argv[]) {
     writer.write(wasm, options.extra["output"]);
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-dis.cpp b/src/tools/wasm-dis.cpp
index bcd7241743b..d69cc1f96cc 100644
--- a/src/tools/wasm-dis.cpp
+++ b/src/tools/wasm-dis.cpp
@@ -109,5 +109,5 @@ int main(int argc, const char* argv[]) {
     std::cerr << "Done." << std::endl;
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index 303664d88d5..7ab7fd55cff 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -290,5 +290,5 @@ int main(int argc, const char* argv[]) {
     writer.write(wasm, output);
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-merge.cpp b/src/tools/wasm-merge.cpp
index d44115399f2..3c354f745bf 100644
--- a/src/tools/wasm-merge.cpp
+++ b/src/tools/wasm-merge.cpp
@@ -833,5 +833,5 @@ Input source maps can be specified by adding an -ism option right after the modu
     writer.write(merged, options.extra["output"]);
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-metadce.cpp b/src/tools/wasm-metadce.cpp
index e12209b4d17..299cb2f63c9 100644
--- a/src/tools/wasm-metadce.cpp
+++ b/src/tools/wasm-metadce.cpp
@@ -675,5 +675,5 @@ int main(int argc, const char* argv[]) {
   // Clean up
   free(copy);
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index 8736f6f0627..d3ba797a674 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -477,7 +477,7 @@ For more on how to optimize effectively, see
       }
     }
 
-    flush_and_quick_exit();
+    flush_and_quick_exit(0);
     return 0;
   }
 
@@ -502,5 +502,5 @@ For more on how to optimize effectively, see
     }
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm-shell.cpp b/src/tools/wasm-shell.cpp
index 8ec13026ace..2750f9d0b1e 100644
--- a/src/tools/wasm-shell.cpp
+++ b/src/tools/wasm-shell.cpp
@@ -604,5 +604,5 @@ int main(int argc, const char* argv[]) {
   std::cerr << "all checks passed.\n";
   Colors::normal(std::cerr);
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }
diff --git a/src/tools/wasm2js.cpp b/src/tools/wasm2js.cpp
index e7da05df890..94faf43c821 100644
--- a/src/tools/wasm2js.cpp
+++ b/src/tools/wasm2js.cpp
@@ -1008,5 +1008,5 @@ int main(int argc, const char* argv[]) {
     std::cerr << "done." << std::endl;
   }
 
-  flush_and_quick_exit();
+  flush_and_quick_exit(0);
 }

From 2db41f6782613efc348425d1ce6a2dd0a7d1a6a5 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 16 Jan 2026 11:31:24 -0800
Subject: [PATCH 08/11] add C flushing

---
 src/support/file.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/support/file.cpp b/src/support/file.cpp
index dbb44afd643..97b68333c1d 100644
--- a/src/support/file.cpp
+++ b/src/support/file.cpp
@@ -137,7 +137,13 @@ size_t wasm::file_size(std::string filename) {
 }
 
 void wasm::flush_and_quick_exit(int code) {
+  // We expect C++ files to be flushed by their destructors already. Flush the
+  // standard streams manually.
   std::cout << std::flush;
   std::cerr << std::flush;
+
+  // To be safe, also flush at the C level.
+  fflush(NULL);
+
   std::quick_exit(code);
 }

From 9a4a61fc6adca320f28697478743eddc3fd53784 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 16 Jan 2026 13:23:05 -0800
Subject: [PATCH 09/11] sanitizers

---
 src/support/file.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/support/file.cpp b/src/support/file.cpp
index 97b68333c1d..be06980d591 100644
--- a/src/support/file.cpp
+++ b/src/support/file.cpp
@@ -145,5 +145,13 @@ void wasm::flush_and_quick_exit(int code) {
   // To be safe, also flush at the C level.
   fflush(NULL);
 
+#if __has_feature(address_sanitizer) || __has_feature(thread_sanitizer) ||     \
+  __has_feature(memory_sanitizer) || __has_feature(leak_sanitizer) ||          \
+  __has_feature(undefined_behavior_sanitizer)
+  // Avoid quick_exit when using sanitizers, so that leak checks and other
+  // things can run during shutdown normally.
+  std::exit(code);
+#else
   std::quick_exit(code);
+#endif
 }

From 387ffb958833f015599485099b4b97748097dc87 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 16 Jan 2026 15:57:21 -0800
Subject: [PATCH 10/11] cause lsan errors?

---
 src/wasm-interpreter.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 89b767af2aa..fa06de5ce7e 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -373,7 +373,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
     // Binaryen is generally not used in long-running programs so we just ignore
     // such leaks for now.
     // TODO: Add a cycle collector?
-    __lsan_ignore_object(allocation.get());
+    //__lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation, type.getHeapType());
   }
@@ -382,7 +382,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
   Literal makeExnData(Tag* tag, const Literals& payload) {
     auto allocation = std::make_shared<ExnData>(tag, payload);
 #if __has_feature(leak_sanitizer) || __has_feature(address_sanitizer)
-    __lsan_ignore_object(allocation.get());
+    //__lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation);
   }
@@ -406,7 +406,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
     // function.
     auto allocation = std::make_shared<FuncData>(name, this);
 #if __has_feature(leak_sanitizer) || __has_feature(address_sanitizer)
-    __lsan_ignore_object(allocation.get());
+    //__lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation, type);
   }
@@ -5206,7 +5206,7 @@ class ModuleRunner : public ModuleRunnerBase<ModuleRunner> {
         return callFunction(name, arguments);
       });
 #if __has_feature(leak_sanitizer) || __has_feature(address_sanitizer)
-    __lsan_ignore_object(allocation.get());
+    //__lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation, type);
   }

From 2cb69105247bdba8891981f8787ca7e5240306a8 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 16 Jan 2026 16:24:20 -0800
Subject: [PATCH 11/11] Revert "cause lsan errors?"

This reverts commit 387ffb958833f015599485099b4b97748097dc87.
---
 src/wasm-interpreter.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index fa06de5ce7e..89b767af2aa 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -373,7 +373,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
     // Binaryen is generally not used in long-running programs so we just ignore
     // such leaks for now.
     // TODO: Add a cycle collector?
-    //__lsan_ignore_object(allocation.get());
+    __lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation, type.getHeapType());
   }
@@ -382,7 +382,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
   Literal makeExnData(Tag* tag, const Literals& payload) {
     auto allocation = std::make_shared<ExnData>(tag, payload);
 #if __has_feature(leak_sanitizer) || __has_feature(address_sanitizer)
-    //__lsan_ignore_object(allocation.get());
+    __lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation);
   }
@@ -406,7 +406,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
     // function.
     auto allocation = std::make_shared<FuncData>(name, this);
 #if __has_feature(leak_sanitizer) || __has_feature(address_sanitizer)
-    //__lsan_ignore_object(allocation.get());
+    __lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation, type);
   }
@@ -5206,7 +5206,7 @@ class ModuleRunner : public ModuleRunnerBase<ModuleRunner> {
         return callFunction(name, arguments);
       });
 #if __has_feature(leak_sanitizer) || __has_feature(address_sanitizer)
-    //__lsan_ignore_object(allocation.get());
+    __lsan_ignore_object(allocation.get());
 #endif
     return Literal(allocation, type);
   }