Fix VC++ 2015 64-bit truncation warning in zlib

third_party/zlib/google.patch

Index: third_party/zlib/google.patch
diff --git a/third_party/zlib/google.patch b/third_party/zlib/google.patch
index 3818b11745073fb8afcf71719c84575fda690983..4388317461ccbfc83fe591a948e92153be8bd5d7 100644
--- a/third_party/zlib/google.patch
+++ b/third_party/zlib/google.patch
@@ -1,3 +1,17 @@
+diff -ru zlib-1.2.5/crc_folding.c zlib/crc_folding.c
+--- zlib-1.2.5/crc_folding.c
++++ zlib/crc_folding.c
+@@ -283,7 +283,9 @@
+         goto partial;
+     }
+
+-    algn_diff = 0 - (unsigned long)src & 0xF;
++    // Double cast to avoid truncation errors in 64-bit builds by making the
++    // truncation explicit.
++    algn_diff = 0 - (unsigned long)(size_t)src & 0xF;
+     if (algn_diff) {
+         xmm_crc_part = _mm_loadu_si128((__m128i *)src);
+         _mm_storeu_si128((__m128i *)dst, xmm_crc_part);
 diff -ru zlib-1.2.5/gzlib.c zlib/gzlib.c
 --- zlib-1.2.5/gzlib.c
 +++ zlib/gzlib.c