add additional tests

Author: a-tarasyuk

clang/test/Sema/main-no-return-c89-1.c

@@ -0,0 +1,10 @@
+/* RUN: %clang_cc1 -std=c89 -fsyntax-only -verify -Wno-strict-prototypes -pedantic %s
+ * RUN: %clang_cc1 -std=c89 -fsyntax-only -verify -Wno-strict-prototypes -Wmain-return-type %s
+ * RUN: %clang_cc1 -std=c89 -fsyntax-only -verify=implicit-main-return -Wno-strict-prototypes -pedantic -Wno-main-return-type %s
+ */
+
+/* implicit-main-return-no-diagnostics */
+
+int main() {
+
+} /* expected-warning {{implicit '0' return value from 'main' is a C99 extension}} */

clang/test/Sema/main-no-return-c89-2.c

@@ -0,0 +1,11 @@
+/* RUN: %clang_cc1 -std=c89 -fsyntax-only -verify -Wno-strict-prototypes -Wmain-return-type %s
+ */
+
+/* expected-no-diagnostics */
+
+void exit(int);
+
+int main() {
+    if (1)
+        exit(1);
+}

clang/test/Sema/main-no-return-c89-3.c

@@ -0,0 +1,8 @@
+/* RUN: %clang_cc1 -std=c89 -fsyntax-only -verify -Wno-strict-prototypes -Wmain-return-type %s
+ */
+
+/* expected-no-diagnostics */
+
+int main() {
+    return 0;
+}