Convert bn_test to C++.

Along the way, fix a host of missing failure checks. This will save some
headache when it comes time to run these under the malloc failure tests.

Change-Id: I3fd589bd094178723398e793d6bc578884e99b67
Reviewed-on: https://boringssl-review.googlesource.com/4126
Reviewed-by: Adam Langley <agl@google.com>

crypto/bn/CMakeLists.txt

@@ -69,7 +69,7 @@ perlasm(armv4-mont.${ASM_EXT} asm/armv4-mont.pl)
 add_executable(
   bn_test
 
-  bn_test.c
+  bn_test.cc
 )
 
 target_link_libraries(bn_test crypto)

crypto/test/scoped_types.h

@@ -18,6 +18,7 @@
 #include <stdint.h>
 
 #include <openssl/bio.h>
+#include <openssl/bn.h>
 #include <openssl/dh.h>
 #include <openssl/evp.h>
 #include <openssl/hmac.h>
@@ -69,6 +70,9 @@ class ScopedOpenSSLContext {
 };
 
 using ScopedBIO = ScopedOpenSSLType<BIO, BIO_vfree>;
+using ScopedBIGNUM = ScopedOpenSSLType<BIGNUM, BN_free>;
+using ScopedBN_CTX = ScopedOpenSSLType<BN_CTX, BN_CTX_free>;
+using ScopedBN_MONT_CTX = ScopedOpenSSLType<BN_MONT_CTX, BN_MONT_CTX_free>;
 using ScopedDH = ScopedOpenSSLType<DH, DH_free>;
 using ScopedEVP_PKEY = ScopedOpenSSLType<EVP_PKEY, EVP_PKEY_free>;
 using ScopedPKCS8_PRIV_KEY_INFO = ScopedOpenSSLType<PKCS8_PRIV_KEY_INFO,

include/openssl/bn.h

@@ -473,7 +473,8 @@ OPENSSL_EXPORT BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w);
   BN_div(NULL, (rem), (numerator), (divisor), (ctx))
 
 /* BN_nnmod is a non-negative modulo function. It acts like |BN_mod|, but 0 <=
- * |rem| < |divisor| is always true. */
+ * |rem| < |divisor| is always true. It returns one on success and zero on
+ * error. */
 OPENSSL_EXPORT int BN_nnmod(BIGNUM *rem, const BIGNUM *numerator,
                             const BIGNUM *divisor, BN_CTX *ctx);