Fix build with GCC 4.9.2 and -Wtype-limits.

gRPC builds on Debian Jessie, which has GCC 4.9.2, and builds with
-Wtype-limits, which makes it warn about code intended for 64-bit
systems when building on 32-bit systems.

We have tried to avoid these issues with Clang previously by guarding
with “sizeof(size_t) > 4”, but this version of GCC isn't smart enough to
figure that out.

Change-Id: I800ceb3891436fa7c81474ede4b8656021568357
Reviewed-on: https://boringssl-review.googlesource.com/28247
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

crypto/fipsmodule/modes/ccm.c

@@ -158,9 +158,7 @@ static int ccm128_init_state(const CCM128_CONTEXT *ctx,
   size_t remaining_blocks = 2 * ((plaintext_len + 15) / 16) + 1;
   if (plaintext_len + 15 < plaintext_len ||
       remaining_blocks + blocks < blocks ||
-      // Silence Clang's unhelpful -Wtautological-constant-out-of-range-compare
-      // warning.
-      (sizeof(size_t) > 4 && remaining_blocks + blocks > UINT64_C(1) << 61)) {
+      (uint64_t) remaining_blocks + blocks > UINT64_C(1) << 61) {
     return 0;
   }
 

ssl/d1_both.cc

@@ -536,6 +536,20 @@ bool dtls1_finish_message(SSL *ssl, CBB *cbb, Array<uint8_t> *out_msg) {
   return true;
 }
 
+// ssl_size_t_greater_than_32_bits returns whether |v| exceeds the bounds of a
+// 32-bit value. The obvious thing doesn't work because, in some 32-bit build
+// configurations, the compiler warns that the test is always false and breaks
+// the build.
+static bool ssl_size_t_greater_than_32_bits(size_t v) {
+#if defined(OPENSSL_64_BIT)
+  return v > 0xffffffff;
+#elif defined(OPENSSL_32_BIT)
+  return false;
+#else
+#error "Building for neither 32- nor 64-bits."
+#endif
+}
+
 // add_outgoing adds a new handshake message or ChangeCipherSpec to the current
 // outgoing flight. It returns true on success and false on error.
 static bool add_outgoing(SSL *ssl, bool is_ccs, Array<uint8_t> data) {
@@ -550,7 +564,7 @@ static bool add_outgoing(SSL *ssl, bool is_ccs, Array<uint8_t> data) {
                     (1 << 8 * sizeof(ssl->d1->outgoing_messages_len)),
                 "outgoing_messages_len is too small");
   if (ssl->d1->outgoing_messages_len >= SSL_MAX_HANDSHAKE_FLIGHT ||
-      static_cast<uint64_t>(data.size()) > 0xffffffff) {
+      ssl_size_t_greater_than_32_bits(data.size())) {
     assert(false);
     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
     return false;

ssl/s3_both.cc

@@ -238,8 +238,8 @@ int ssl3_flush_flight(SSL *ssl) {
     return -1;
   }
 
-  if (static_cast<uint64_t>(ssl->s3->pending_flight->length) > 0xffffffff ||
-      ssl->s3->pending_flight->length > INT_MAX) {
+  static_assert(INT_MAX <= 0xffffffff, "int is larger than 32 bits");
+  if (ssl->s3->pending_flight->length > INT_MAX) {
     OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
     return -1;
   }