printf format checking for msvc

Summary:
sal annotations can be used to do similar (not exact) checking to the functionality provided by the format attribute in gcc
the annotations are done by prefixing the format string with a value which makes the macro definitions a bit messy

@override-unit-failures

Test Plan: fbconfig -r folly && fbmake runtests

Reviewed By: delong.j@fb.com

FB internal diff: D1313653

folly/Portability.h

@@ -45,6 +45,21 @@ struct MaxAlign { char c; } __attribute__((aligned));
 // compiler specific attribute translation
 // msvc should come first, so if clang is in msvc mode it gets the right defines
 
+// NOTE: this will only do checking in msvc with versions that support /analyze
+#if _MSC_VER
+# ifdef _USE_ATTRIBUTES_FOR_SAL
+#    undef _USE_ATTRIBUTES_FOR_SAL
+# endif
+# define _USE_ATTRIBUTES_FOR_SAL 1
+# include <sal.h>
+# define FOLLY_PRINTF_FORMAT _Printf_format_string_
+# define FOLLY_PRINTF_FORMAT_ATTR(format_param, dots_param) /**/
+#else
+# define FOLLY_PRINTF_FORMAT /**/
+# define FOLLY_PRINTF_FORMAT_ATTR(format_param, dots_param) \
+  __attribute__((format(printf, format_param, dots_param)))
+#endif
+
 // noreturn
 #if defined(_MSC_VER)
 # define FOLLY_NORETURN __declspec(noreturn)

folly/String.h

@@ -173,16 +173,16 @@ String uriUnescape(StringPiece str, UriEscapeMode mode = UriEscapeMode::ALL) {
  * resulting string, and the second appends the produced characters to
  * the specified string and returns a reference to it.
  */
-std::string stringPrintf(const char* format, ...)
-  __attribute__ ((format (printf, 1, 2)));
+std::string stringPrintf(FOLLY_PRINTF_FORMAT const char* format, ...)
+  FOLLY_PRINTF_FORMAT_ATTR(1, 2);
 
-/** Similar to stringPrintf, with different signiture.
-  */
-void stringPrintf(std::string* out, const char* fmt, ...)
-  __attribute__ ((format (printf, 2, 3)));
+/* Similar to stringPrintf, with different signature. */
+void stringPrintf(std::string* out, FOLLY_PRINTF_FORMAT const char* fmt, ...)
+  FOLLY_PRINTF_FORMAT_ATTR(2, 3);
 
-std::string& stringAppendf(std::string* output, const char* format, ...)
-  __attribute__ ((format (printf, 2, 3)));
+std::string& stringAppendf(std::string* output,
+                          FOLLY_PRINTF_FORMAT const char* format, ...)
+  FOLLY_PRINTF_FORMAT_ATTR(2, 3);
 
 /**
  * Backslashify a string, that is, replace non-printable characters