If an object (such as a std::string) with an appropriate c_str() member function

is passed to a variadic function in a position where a format string indicates
that c_str()'s return type is desired, provide a note suggesting that the user
may have intended to call the c_str() member.

Factor the non-POD-vararg checking out of DefaultVariadicArgumentPromotion and
move it to SemaChecking in order to facilitate this. Factor the call checking
out of function call checking and block call checking, and extend it to cover
constructor calls too.

Patch by Sam Panzer!

llvm-svn: 158887

1 files changed, 18 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/printf-block.cpp b/clang/test/SemaCXX/printf-block.cpp
new file mode 100644
index 00000000000..a7d266bac5c
--- /dev/null
+++ b/clang/test/SemaCXX/printf-block.cpp
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -fsyntax-only -fblocks -Wformat -verify %s -Wno-error=non-pod-varargs
+
+int (^block) (int, const char *,...) __attribute__((__format__(__printf__,2,3))) = ^ __attribute__((__format__(__printf__,2,3))) (int arg, const char *format,...) {return 5;};
+
+class HasNoCStr {
+  const char *str;
+ public:
+  HasNoCStr(const char *s): str(s) { }
+  const char *not_c_str() {return str;}
+};
+
+void test_block() {
+  const char str[] = "test";
+  HasNoCStr hncs(str);
+  int n = 4;
+  block(n, "%s %d", str, n); // no-warning
+  block(n, "%s %s", hncs, n); // expected-warning{{cannot pass non-POD object of type 'HasNoCStr' to variadic function; expected type from format string was 'char *'}} expected-warning{{format specifies type 'char *' but the argument has type 'int'}}
+}