test: Update lib_dlopen2 test case (t200)

It has a couple problems.  First, the filter should be set for the main
function, there's no function called 'a'.  And the 'creat' function is
not the syscall so it should not fix up it to match creat64 in libc.

Finally, it seems GCC optimized out the Parent construction as it does
nothing.  clang seems to keep it, so let's handle it in the fixup().

The failed output looked like below:
    t200_lib_dlopen2: diff result of g++ -pg -O1 -g -fno-ipa-sra
    --- expect	2024-03-02 12:33:32.381859085 -0800
    +++ result	2024-03-02 12:33:32.381859085 -0800
    @@ -3,7 +3,5 @@
        dlsym();
    -   creat64() {
    -     Child::Child() {
    -       Parent::Parent();
    -     } /* Child::Child */
    -   } /* creat64 */
    +   creat() {
    +     Child::Child();
    +   } /* creat */
        Child::func();

Signed-off-by: Namhyung Kim <namhyung@gmail.com>

tests/s-dlopen2.cpp

@@ -11,7 +11,7 @@ class Parent {
 int main(int argc, char *argv[])
 {
 	void *handle;
-	Parent *(*creat)();
+	Parent *(*create)();
 	Parent *p;
 	int n = 1;
 
@@ -23,9 +23,9 @@ int main(int argc, char *argv[])
 	if (!handle)
 		return -1;
 
-	creat = (Parent * (*)()) dlsym(handle, "creat");
-	p = creat();
-	p->bar(n);
+	create = (Parent * (*)()) dlsym(handle, "create");
+	p = create();
+	p->bar(n); // calls func() which is defined in Child
 	dlclose(handle);
 
 	return 0;

tests/s-libbaz.cpp

@@ -14,7 +14,7 @@ int Child::func(int n)
 	return 100;
 }
 
-extern "C" Parent *creat()
+extern "C" Parent *create()
 {
 	return new Child;
 }

tests/t200_lib_dlopen2.py

@@ -13,11 +13,11 @@ def __init__(self):
             [ 29510] | main() {
  398.509 us [ 29510] |   dlopen();
    2.324 us [ 29510] |   dlsym();
-            [ 29510] |   creat() {
+            [ 29510] |   create() {
             [ 29510] |     Child::Child() {
    0.290 us [ 29510] |       Parent::Parent();
    1.703 us [ 29510] |     } /* Child::Child */
-   6.090 us [ 29510] |   } /* creat */
+   6.090 us [ 29510] |   } /* create */
    0.133 us [ 29510] |   Child::func();
   48.519 us [ 29510] |   dlclose();
  465.432 us [ 29510] | } /* main */
@@ -33,7 +33,12 @@ def build(self, name, cflags='', ldflags=''):
                                       cflags, ldflags)
 
     def setup(self):
-        self.option = '-F a'
+        self.option = '-F main'
 
     def fixup(self, cflags, result):
-        return result.replace('creat', 'creat64')
+        # GCC seems to optimize out the empty Parent::Parent().
+        return result.replace("""
+            [ 29510] |     Child::Child() {
+   0.290 us [ 29510] |       Parent::Parent();
+   1.703 us [ 29510] |     } /* Child::Child */""", """
+   1.703 us [ 29510] |     Child::Child();""")