Add infrastructure for reference counts.
OpenSSL has traditionally done reference counting with |int|s and the
|CRYPTO_add| function. Unless a special callback is installed (rare),
this is implemented by doing the reference count operations under a
lock.
This change adds infrastructure for handling reference counts and uses
atomic operations when C11 support is available.
Change-Id: Ia023ce432319efd00f77a7340da27d16ee4b63c3
Reviewed-on: https://boringssl-review.googlesource.com/4771
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/thread.h b/include/openssl/thread.h
index f6e7529..01df6ea 100644
--- a/include/openssl/thread.h
+++ b/include/openssl/thread.h
@@ -90,6 +90,15 @@
} CRYPTO_MUTEX;
#endif
+/* CRYPTO_refcount_t is the type of a reference count.
+ *
+ * Since some platforms use C11 atomics to access this, it should have the
+ * _Atomic qualifier. However, this header is included by C++ programs as well
+ * as C code that might not set -std=c11. So, in practice, it's not possible to
+ * do that. Instead we statically assert that the size and native alignment of
+ * a plain uint32_t and an _Atomic uint32_t are equal in refcount_c11.c. */
+typedef uint32_t CRYPTO_refcount_t;
+
/* Functions to support multithreading.
*
