Add back-and-forth inflateCopy() test

Check that calling inflateCopy() twice does not result in memory
corruption.

test/CMakeLists.txt

@@ -175,6 +175,7 @@ if(WITH_GTEST)
             test_deflate_tune.cc
             test_dict.cc
             test_inflate_adler32.cc
+            test_inflate_copy.cc
             test_large_buffers.cc
             test_raw.cc
             test_small_buffers.cc

test/test_inflate_copy.cc

@@ -0,0 +1,31 @@
+/* test_inflate_copy.cc - Test copying inflate stream */
+
+#include "zbuild.h"
+#ifdef ZLIB_COMPAT
+#  include "zlib.h"
+#else
+#  include "zlib-ng.h"
+#endif
+
+#include "test_shared.h"
+
+#include <gtest/gtest.h>
+
+TEST(inflate, copy_back_and_forth) {
+    PREFIX3(stream) d1_stream, d2_stream;
+    int err;
+
+    memset(&d1_stream, 0, sizeof(d1_stream));
+    err = PREFIX(inflateInit2)(&d1_stream, MAX_WBITS + 14);
+    ASSERT_EQ(err, Z_OK);
+    err = PREFIX(inflateCopy)(&d2_stream, &d1_stream);
+    ASSERT_EQ(err, Z_OK);
+    err = PREFIX(inflateEnd)(&d1_stream);
+    ASSERT_EQ(err, Z_OK);
+    err = PREFIX(inflateCopy)(&d1_stream, &d2_stream);
+    ASSERT_EQ(err, Z_OK);
+    err = PREFIX(inflateEnd)(&d1_stream);
+    ASSERT_EQ(err, Z_OK);
+    err = PREFIX(inflateEnd)(&d2_stream);
+    ASSERT_EQ(err, Z_OK);
+}