[EH/SjLj] Add tests for mixing exceptions and sjlj (#14732)

This adds three tests for mixing exceptions and sjlj. We currently pass
`test_exceptions_longjmp1`, and other two tests will pass after
llvm/llvm-project@c285a11.

- `test_exceptions_longjmp1`
  In a function with a `setjmp` call, `invoke` exists in LLVM IR. We
  have to check both for EH and sjlj when a function throws.
- `test_exceptions_longjmp2`
  In a function without a `setjmp` call, `invoke` exists in LLVM IR. We
  only have to handle exceptions, but when longjmps occur, we shouldn't
  swallow them.
- `test_exceptions_longjmp3`
  In a function with a `setjmp` call, there's no `invoke` in LLVM IR. We
  only have to handle longjmps, but w hen an exceptions occcur, we
  shouldn't swallow them.

Each of these tests corresponds with tests in
test/CodeGen/WebAssembly/lower-em-sjlj.ll in
llvm/llvm-project@c285a11.

tests/core/test_exceptions_longjmp1.cpp

@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <setjmp.h>
+
+static jmp_buf buf;
+
+void foo() {
+  longjmp(buf, 1);
+}
+
+int main() {
+  int jmpval = setjmp(buf);
+  if (jmpval != 0) {
+    printf("setjmp returned for the second time\n");
+    return 0;
+  }
+  try {
+    foo();
+  } catch (...) {
+  }
+  return 0;
+}

tests/core/test_exceptions_longjmp1.out

@@ -0,0 +1 @@
+setjmp returned for the second time

tests/core/test_exceptions_longjmp2.cpp

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <setjmp.h>
+
+static jmp_buf buf;
+
+void foo() {
+  longjmp(buf, 1);
+}
+
+void test() {
+  try {
+    foo();
+  } catch (...) {
+  }
+}
+
+int main() {
+  int jmpval = setjmp(buf);
+  if (jmpval != 0) {
+    printf("setjmp returned for second time\n");
+    return 0;
+  }
+  test();
+  return 0;
+}

tests/core/test_exceptions_longjmp2.out

@@ -0,0 +1 @@
+setjmp returned for second time

tests/core/test_exceptions_longjmp3.cpp

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <setjmp.h>
+
+static jmp_buf buf;
+
+void foo() {
+  throw 3;
+}
+
+void test() {
+  int jmpval = setjmp(buf);
+  if (jmpval != 0) {
+    printf("setjmp returned for 2nd time\n");
+    return;
+  }
+  foo();
+}
+
+int main() {
+  try {
+    test();
+  } catch (int n) {
+    printf("caught: %d\n", n);
+  }
+  return 0;
+}

tests/core/test_exceptions_longjmp3.out

@@ -0,0 +1 @@
+caught: 3

tests/test_core.py

@@ -1413,6 +1413,21 @@ def test_iostream_ctors(self):
 }
 ''', 'bugfree code')
 
+  def test_exceptions_longjmp1(self):
+    self.set_setting('SUPPORT_LONGJMP')
+    self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
+    self.do_core_test('test_exceptions_longjmp1.cpp')
+
+  def test_exceptions_longjmp2(self):
+    self.set_setting('SUPPORT_LONGJMP')
+    self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
+    self.do_core_test('test_exceptions_longjmp2.cpp')
+
+  def test_exceptions_longjmp3(self):
+    self.set_setting('SUPPORT_LONGJMP')
+    self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
+    self.do_core_test('test_exceptions_longjmp3.cpp')
+
   # Marked as impure since the WASI reactor modules (modules without main)
   # are not yet suppored by the wasm engines we test against.
   @also_with_standalone_wasm(impure=True)