Define |OPENSSL_PRINTF_FORMAT_FUNC| for format string annotations.

This centralizes the conditional logic into openssl/base.h so that it
doesn't have to be repeated. The name |OPENSSL_PRINTF_FORMAT_FUNC| was
chosen in anticipation of eventually defining an
|OPENSSL_PRINTF_FORMAT_ARG| for MSVC-style parameter annotations.

Change-Id: I273e6eddd209e696dc9f82099008c35b6d477cdb
Reviewed-on: https://boringssl-review.googlesource.com/6909
Reviewed-by: David Benjamin <davidben@google.com>

include/openssl/base.h

diff --git a/include/openssl/base.h b/include/openssl/base.h
index 47b3ccb..65ab3f7 100644
--- a/include/openssl/base.h
+++ b/include/openssl/base.h
@@ -138,6 +138,15 @@
 
 #endif  /* defined(BORINGSSL_SHARED_LIBRARY) */
 
+
+#if defined(__GNUC__)
+#define OPENSSL_PRINTF_FORMAT_FUNC(string_index, first_to_check) \
+        __attribute__((format(printf, string_index, first_to_check)))
+#else
+#define OPENSSL_PRINTF_FORMAT_FUNC(string_index, first_to_check)
+#endif
+
+
 /* CRYPTO_THREADID is a dummy value. */
 typedef int CRYPTO_THREADID;
 

include/openssl/bio.h

diff --git a/include/openssl/bio.h b/include/openssl/bio.h
index c88a3e1..0c8bfe4 100644
--- a/include/openssl/bio.h
+++ b/include/openssl/bio.h
@@ -312,14 +312,8 @@
  *
  * These functions are versions of printf functions that output to a BIO rather
  * than a FILE. */
-#ifdef __GNUC__
-#define __bio_h__attr__ __attribute__
-#else
-#define __bio_h__attr__(x)
-#endif
 OPENSSL_EXPORT int BIO_printf(BIO *bio, const char *format, ...)
-    __bio_h__attr__((__format__(__printf__, 2, 3)));
-#undef __bio_h__attr__
+    OPENSSL_PRINTF_FORMAT_FUNC(2, 3);
 
 
 /* Utility functions. */

include/openssl/mem.h

diff --git a/include/openssl/mem.h b/include/openssl/mem.h
index c8e2b3e..46d75d1 100644
--- a/include/openssl/mem.h
+++ b/include/openssl/mem.h
@@ -119,18 +119,12 @@
  * These functions are either OpenSSL wrappers for standard functions (i.e.
  * |BIO_snprintf| and |BIO_vsnprintf|) which don't exist in C89, or are
  * versions of printf functions that output to a BIO rather than a FILE. */
-#ifdef __GNUC__
-#define __bio_h__attr__ __attribute__
-#else
-#define __bio_h__attr__(x)
-#endif
 OPENSSL_EXPORT int BIO_snprintf(char *buf, size_t n, const char *format, ...)
-    __bio_h__attr__((__format__(__printf__, 3, 4)));
+    OPENSSL_PRINTF_FORMAT_FUNC(3, 4);
 
 OPENSSL_EXPORT int BIO_vsnprintf(char *buf, size_t n, const char *format,
                                  va_list args)
-    __bio_h__attr__((__format__(__printf__, 3, 0)));
-#undef __bio_h__attr__
+    OPENSSL_PRINTF_FORMAT_FUNC(3, 0);
 
 
 #if defined(__cplusplus)