commit 1a9bc441270732fd89e2a2d268c122ade759d7f9
author Brian Smith <brian@briansmith.org> Mon Mar 16 19:27:05 2015 -1000
committer Adam Langley <agl@google.com> Mon Apr 13 20:29:05 2015 +0000
tree 8032f6132738e280f22c7444dabfef41f8b2f992
parent 655764a22a9fdcb130d37744c8883776a32f08b5

Fix standalone Windows release-mode builds.

`cmake -GNinja .. -DCMAKE_BUILD_TYPE=Release` fails without this
patch, when building using MSVC 2013.

MSVC will detect (in release builds only, it seems) that functions that
call abort will never return, and then warn that any code after a call
to one of them is unreachable. Since we treat warnings as errors when
building, this breaks the build. While this is usually desirable, it
isn't desirable in this case.

Change-Id: Ie5f24b1beb60fd2b33582a2ceef4c378ad0678fb
Reviewed-on: https://boringssl-review.googlesource.com/3960
Reviewed-by: Adam Langley <agl@google.com>

crypto/cipher/e_aes.c

diff --git a/crypto/cipher/e_aes.c b/crypto/cipher/e_aes.c
index 6e4b7a0..9988345 100644
--- a/crypto/cipher/e_aes.c
+++ b/crypto/cipher/e_aes.c
@@ -283,7 +283,8 @@
 #endif
 
 static int aes_init_key(EVP_CIPHER_CTX *ctx, const uint8_t *key,
-                        const uint8_t *iv, int enc) {
+                        const uint8_t *iv, int enc)
+                        OPENSSL_SUPPRESS_UNREACHABLE_CODE_WARNINGS {
   int ret, mode;
   EVP_AES_KEY *dat = (EVP_AES_KEY *)ctx->cipher_data;
 
@@ -404,7 +405,8 @@
 
 static ctr128_f aes_ctr_set_key(AES_KEY *aes_key, GCM128_CONTEXT *gcm_ctx,
                                 block128_f *out_block, const uint8_t *key,
-                                size_t key_len) {
+                                size_t key_len)
+                                OPENSSL_SUPPRESS_UNREACHABLE_CODE_WARNINGS {
   if (aesni_capable()) {
     aesni_set_encrypt_key(key, key_len * 8, aes_key);
     if (gcm_ctx != NULL) {

crypto/internal.h

diff --git a/crypto/internal.h b/crypto/internal.h
index 30e6e92..38f9820 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -120,6 +120,26 @@
 #endif
 
 
+/* MSVC will sometimes correctly detect unreachable code and issue a warning,
+ * which breaks the build since we treat errors as warnings, in some rare cases
+ * where we want to allow the dead code to continue to exist. In these
+ * situations, annotate the function containing the unreachable code with
+ * OPENSSL_SUPPRESS_UNREACHABLE_CODE_WARNINGS after its parameters:
+ *
+ *    void f() OPENSSL_SUPPRESS_UNREACHABLE_CODE_WARNINGS {
+ *       ...
+ *    }
+ *
+ * Note that MSVC's reachability analysis seems to operate on a whole-function
+ * basis, so the annotation must be placed on the entire function, not just a
+ * block within the function. */
+#if defined(_MSC_VER)
+#define OPENSSL_SUPPRESS_UNREACHABLE_CODE_WARNINGS \
+        __pragma(warning(suppress:4702))
+#else
+#define OPENSSL_SUPPRESS_UNREACHABLE_CODE_WARNINGS
+#endif
+
 /* st_CRYPTO_EX_DATA_IMPL contains an ex_data implementation. See the comments
  * in ex_data.h for details of the behaviour of each of the functions. */
 struct st_CRYPTO_EX_DATA_IMPL {