Add tests for dyncall_so patch (#908)

emsdk/patches/dynCall_so.patch

@@ -1,3 +1,5 @@
+Tests for this are in emsdk/tests/test_dyncall.py
+
 --- a/emsdk/fastcomp/emscripten/src/support.js
 +++ b/emsdk/fastcomp/emscripten/src/support.js
 @@ -338,6 +338,11 @@ function relocateExports(exports, memoryBase, tableBase, moduleLocal) {

emsdk/tests/common.py

@@ -16,3 +16,28 @@ env = {
     "EM_CACHE": str(EMSDK / ".emscripten_cache"),
     "BINARYEN_ROOT": str(EMSDK / "binaryen"),
 }
+
+MAIN_C = """
+#include <stdio.h>
+#include <dlfcn.h>
+
+int main() {
+  puts("hello from main");
+  void *handle = dlopen("library.wasm", RTLD_NOW);
+  if (!handle) {
+    puts("cannot load side module");
+    puts(dlerror());
+    return 1;
+  }
+  typedef void (*type_v)();
+  type_v side_func = (type_v) dlsym(handle, "foo");
+  if (!side_func) {
+    puts("cannot load side function");
+    puts(dlerror());
+    return 1;
+  } else {
+    side_func();
+  }
+  return 0;
+}
+"""

emsdk/tests/test_dyncall.py

@@ -0,0 +1,75 @@
+import subprocess
+from . import common
+
+
+def test_emulate_function(tmpdir):
+    with tmpdir.as_cwd():
+        with open("library.c", "w") as f:
+            f.write(
+                """\
+#include <stdio.h>
+#include <stdlib.h>
+#include <setjmp.h>
+#include <assert.h>
+
+// This can be any function that has a signature not found in main.
+__attribute__ ((noinline)) int indirect_function(int a, float b, int c, double d) {
+  return a;
+}
+
+typedef int (*type_iifid) (int, float, int, double);
+
+void foo() {
+  // Hack to force inclusion of malloc
+  volatile int x = (int) malloc(1);
+  free((void *) x);
+
+  type_iifid fp = &indirect_function;
+
+  jmp_buf buf;
+  int i = setjmp(buf);
+
+  printf("%d\\n", i);
+  assert(fp(i, 0, 0, 0) == i);
+
+  if (i == 0) longjmp(buf, 1);
+}
+"""
+            )
+        with open("main.c", "w") as f:
+            f.write(common.MAIN_C)
+
+        subprocess.run(
+            [
+                "emcc",
+                "-s",
+                "SIDE_MODULE=1",
+                "library.c",
+                "-o",
+                "library.wasm",
+                "-s",
+                "EMULATE_FUNCTION_POINTER_CASTS=1",
+                "-s",
+                "EXPORT_ALL=1",
+            ],
+            check=True,
+            env=common.env,
+        )
+        subprocess.run(
+            [
+                "emcc",
+                "-s",
+                "MAIN_MODULE=1",
+                "main.c",
+                "--embed-file",
+                "library.wasm",
+                "-s",
+                "EMULATE_FUNCTION_POINTER_CASTS=1",
+            ],
+            check=True,
+            env=common.env,
+        )
+        out = subprocess.run(
+            ["node", "a.out.js"], capture_output=True, check=True, env=common.env
+        )
+        assert out.stdout == b"hello from main\n0\n4\n"

emsdk/tests/test_emulate.py

@@ -14,31 +14,8 @@ void foo() {
 }"""
             )
         with open("main.c", "w") as f:
-            f.write(
-                """\
-#include <stdio.h>
-#include <dlfcn.h>
+            f.write(common.MAIN_C)
 
-int main() {
-  puts("hello from main");
-  void *f = dlopen("library.wasm", RTLD_NOW);
-  if (!f) {
-    puts("cannot load side module");
-    puts(dlerror());
-    return 1;
-  }
-  typedef void (*voidfunc)();
-  voidfunc g = (voidfunc) dlsym(f, "foo");
-  if (!g) {
-    puts("cannot load side function");
-    return 1;
-  } else {
-    g();
-  }
-  return 0;
-}
-"""
-            )
         subprocess.run(
             [
                 "emcc",