[runtimes] Use int main(int, char**) consistently in tests

This is needed when running the tests in Freestanding mode, where main()
isn't treated specially. In Freestanding, main() doesn't get mangled as
extern "C", so whatever runtime we're using fails to find the entry point.

One way to solve this problem is to define a symbol alias from __Z4mainiPPc
to _main, however this requires all definitions of main() to have the same
mangling. Hence this commit.

Author: ldionne

libcxx/test/libcxx/depr/depr.c.headers/math_h.compile.pass.cpp

@@ -24,5 +24,3 @@
 #       error M_PI not defined
 #   endif
 #endif
-
-int main() { }

libcxx/test/libcxx/depr/depr.c.headers/stdint_h.std_types_t.compile.pass.cpp

@@ -261,5 +261,3 @@
 #ifndef UINTMAX_C
 #error UINTMAX_C not defined
 #endif
-
-int main() { }

libcxx/test/libcxx/depr/depr.c.headers/stdint_h.xopen_source.compile.pass.cpp

@@ -258,5 +258,3 @@
 #ifndef UINTMAX_C
 #error UINTMAX_C not defined
 #endif
-
-int main() { }

libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.comparison.merged.sh.cpp

@@ -32,12 +32,13 @@ void register2();
 #elif defined(MAIN)
   std::vector<std::type_index> registry;
 
-  int main() {
+  int main(int, char**) {
     register1();
     register2();
 
     assert(registry.size() == 2);
     assert(registry[0] != registry[1]);
+    return 0;
   }
 #else
 # error

libcxx/test/libcxx/language.support/support.rtti/type.info/type_info.comparison.unmerged.sh.cpp

@@ -32,12 +32,13 @@ void register2();
 #elif defined(MAIN)
   std::vector<std::type_index> registry;
 
-  int main() {
+  int main(int, char**) {
     register1();
     register2();
 
     assert(registry.size() == 2);
     assert(registry[0] == registry[1]);
+    return 0;
   }
 #else
 # error

libcxx/test/libcxx/min_max_macros.compile.pass.cpp

@@ -285,5 +285,3 @@ TEST_MACROS();
 TEST_MACROS();
 #include <ext/hash_set>
 TEST_MACROS();
-
-int main() { }

libcxx/test/libcxx/no_assert_include.compile.pass.cpp

@@ -170,5 +170,3 @@
 #ifdef assert
 #error "Do not include cassert or assert.h in standard header files"
 #endif
-
-int main() { }

libcxx/test/libcxx/numerics/clamp_to_integral.pass.cpp

@@ -77,7 +77,7 @@ void test_float() {
   }
 }
 
-int main() {
+int main(int, char**) {
   test<short>();
   test<unsigned short>();
   test<int>();
@@ -87,4 +87,5 @@ int main() {
   test_float<short>();
   test_float<int>();
   test_float<long long>();
+  return 0;
 }

libcxx/test/libcxx/selftest/compile.fail.cpp/compile-error.compile.fail.cpp

@@ -11,4 +11,4 @@
 struct Foo { };
 typedef Foo::x x;
 
-int main() { }
+int main(int, char**) { return 0; }

libcxx/test/libcxx/selftest/compile.fail.cpp/compile-success.compile.fail.cpp

@@ -10,4 +10,4 @@
 
 // Make sure the test DOES NOT pass if it succeeds at compile-time
 
-int main() { }
+int main(int, char**) { return 0; }