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!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158887 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 53 insertions, 0 deletions

diff --git a/test/SemaCXX/printf-cstr.cpp b/test/SemaCXX/printf-cstr.cpp
new file mode 100644
index 0000000000..efb2f704e1
--- /dev/null
+++ b/test/SemaCXX/printf-cstr.cpp
@@ -0,0 +1,53 @@
+// RUN: %clang_cc1 -fsyntax-only -Wformat -verify %s -Wno-error=non-pod-varargs
+
+#include <stdarg.h>
+
+extern "C" {
+extern int printf(const char *restrict, ...);
+extern int sprintf(char *, const char *restrict, ...);
+}
+
+class HasCStr {
+  const char *str;
+ public:
+  HasCStr(const char *s): str(s) { }
+  const char *c_str() {return str;}
+};
+
+class HasNoCStr {
+  const char *str;
+ public:
+  HasNoCStr(const char *s): str(s) { }
+  const char *not_c_str() {return str;}
+};
+
+extern const char extstr[16];
+void pod_test() {
+  char str[] = "test";
+  char dest[32];
+  char formatString[] = "non-const %s %s";
+  HasCStr hcs(str);
+  HasNoCStr hncs(str);
+  int n = 10;
+
+  printf("%d: %s\n", n, hcs.c_str());
+  printf("%d: %s\n", n, hcs); // expected-warning{{cannot pass non-POD object of type 'HasCStr' to variadic function; expected type from format string was 'char *'}} expected-note{{did you mean to call the c_str() method?}}
+  printf("%d: %s\n", n, hncs); // expected-warning{{cannot pass non-POD object of type 'HasNoCStr' to variadic function; expected type from format string was 'char *'}}
+  sprintf(str, "%d: %s", n, hcs); // expected-warning{{cannot pass non-POD object of type 'HasCStr' to variadic function; expected type from format string was 'char *'}} expected-note{{did you mean to call the c_str() method?}}
+
+  printf(formatString, hcs, hncs); // expected-warning{{cannot pass object of non-POD type 'HasCStr' through variadic function}} expected-warning{{cannot pass object of non-POD type 'HasNoCStr' through variadic function}}
+  printf(extstr, hcs, n); // expected-warning{{cannot pass object of non-POD type 'HasCStr' through variadic function}}
+}
+
+struct Printf {
+  Printf();
+  Printf(const Printf&);
+  Printf(const char *,...) __attribute__((__format__(__printf__,2,3)));
+};
+
+void constructor_test() {
+  const char str[] = "test";
+  HasCStr hcs(str);
+  Printf p("%s %d %s", str, 10, 10); // expected-warning {{format specifies type 'char *' but the argument has type 'int'}}
+  Printf q("%s %d", hcs, 10); // expected-warning {{cannot pass non-POD object of type 'HasCStr' to variadic function; expected type from format string was 'char *'}} expected-note{{did you mean to call the c_str() method?}}
+}