Require source files define __STDC_FORMAT_MACROS to use BN FMT macros.
inttypes.h kindly requires a feature macro in C++ on some platforms, due
to a bizarre footnote in C99 (see footnote 191 in section 7.8.1). As
bn.h is a public header, we must leak this wart to the consumer. On
platforms with unfriendly inttypes.h headers, using BN_DEC_FMT1 and
friends now require the feature macro be defined externally.
This broke the Chromium Android Clang builder:
http://build.chromium.org/p/chromium.linux/builders/Android%20Clang%20Builder%20%28dbg%29/builds/59288
Change-Id: I88275a6788c7babd0eae32cae86f115bfa93a591
Reviewed-on: https://boringssl-review.googlesource.com/4688
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/bn.h b/include/openssl/bn.h
index 18aba5f..2cd0224 100644
--- a/include/openssl/bn.h
+++ b/include/openssl/bn.h
@@ -139,7 +139,12 @@
* will allow you to work with numbers until you run out of memory. */
-/* BN_ULONG is the native word size when working with big integers. */
+/* BN_ULONG is the native word size when working with big integers.
+ *
+ * Note: on some platforms, inttypes.h does not define print format macros in
+ * C++ unless |__STDC_FORMAT_MACROS| defined. As this is a public header, bn.h
+ * does not define |__STDC_FORMAT_MACROS| itself. C++ source files which use the
+ * FMT macros must define it externally. */
#if defined(OPENSSL_64_BIT)
#define BN_ULONG uint64_t
#define BN_BITS2 64
