[Sema] Don't crash on scanf on forward-declared enums.

This is valid in GNU C, which allows pointers to incomplete enums. GCC
just pretends that the underlying type is 'int' in those cases, follow
that behavior.

llvm-svn: 279374

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/test/Sema/format-strings-enum.c b/clang/test/Sema/format-strings-enum.c
index e79f8598ab4..ba077a887e0 100644
--- a/clang/test/Sema/format-strings-enum.c
+++ b/clang/test/Sema/format-strings-enum.c
@@ -11,6 +11,7 @@
 #endif
 
 EXTERN_C int printf(const char *,...);
+EXTERN_C int scanf(const char *, ...);
 
 typedef enum { Constant = 0 } TestEnum;
 // Note that in C, the type of 'Constant' is 'int'. In C++ it is 'TestEnum'.
@@ -34,3 +35,18 @@ void testLong(LongEnum input) {
   printf("%lu", input);
   printf("%lu", LongConstant);
 }
+
+#ifndef __cplusplus
+// GNU C allows forward declaring enums.
+extern enum forward_declared *fwd;
+
+void forward_enum() {
+  printf("%u", fwd); // expected-warning{{format specifies type 'unsigned int' but the argument has type 'enum forward_declared *}}
+  printf("%p", fwd);
+
+  scanf("%c", fwd); // expected-warning{{format specifies type 'char *' but the argument has type 'enum forward_declared *}}
+  scanf("%u", fwd);
+  scanf("%lu", fwd); // expected-warning{{format specifies type 'unsigned long *' but the argument has type 'enum forward_declared *}}
+  scanf("%p", fwd); // expected-warning{{format specifies type 'void **' but the argument has type 'enum forward_declared *}}
+}
+#endif