Add mechanism for deprecated declarations.

This allows us to mark functions as deprecated
declarations with OPENSSL_DEPRECATED.

We also add an OPENSSL_BEGIN_ALLOW_DEPRECATED and an
OPENSSL_END_ALLOW_DEPRECATED for testing use to
test deprecated functions.

The purpose of this is to allow us to mark things
people should not be using as deprecated, and force some
inconvenience on the user of such things to notice them
(as opposed to a only a warning to not use it that they
may not see or read without something tripping them up.)

The intent is to still allow use, with some effort,
before removing the function, or moving it to
libdecrepit.

We initially mark X509V3_EXT_add and X509V3_EXT_add_alias
as deprecated.

Update-Note: We are starting to mark some functions in
boringssl as deprecated declarations which will cause the
compiler to emit warnings if they are used. The intention
is both to prevent accidental use in new code, and to to call
attention to call sites in existing code so that the documentation
for the deprecated function can be revisted and appropriate action
taken.

Bug: 584
Change-Id: Ia9ff386f0d22588e8a5999eda1a48b8c28dca2de
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/58405
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Bob Beck <bbe@google.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/crypto/crypto_test.cc b/crypto/crypto_test.cc
index caccba5..4543d5c 100644
--- a/crypto/crypto_test.cc
+++ b/crypto/crypto_test.cc
@@ -158,3 +158,12 @@ TEST(Crypto, OnDemandIntegrityTest) {
   BORINGSSL_integrity_test();
 }
 #endif
+
+OPENSSL_DEPRECATED static void DeprecatedFunction() {}
+
+OPENSSL_BEGIN_ALLOW_DEPRECATED
+TEST(CryptoTest, DeprecatedFunction) {
+  // This is deprecated, but should not trigger any warnings.
+  DeprecatedFunction();
+}
+OPENSSL_END_ALLOW_DEPRECATED