lib,lib-test: stop calling memcmp and memcpy with NULL in tests

src/lib-test/test-common.c

@@ -72,8 +72,10 @@ static ssize_t test_read(struct istream_private *stream)
 			stream->buffer = stream->w_buffer;
 			stream->buffer_size = cur_max;
 		}
-		memcpy(stream->w_buffer + new_skip_diff, tstream->orig_buffer,
-		       cur_max - new_skip_diff);
+		ssize_t size = cur_max - new_skip_diff;
+		if (size > 0)
+			memcpy(stream->w_buffer + new_skip_diff,
+				tstream->orig_buffer, (size_t)size);
 
 		ret = cur_max - stream->pos;
 		stream->pos = cur_max;

src/lib/test-istream-base64-decoder.c

@@ -43,7 +43,9 @@ decode_test(const char *base64_input, const char *output, bool broken_input)
 		    (input->stream_errno == EINVAL && broken_input));
 
 	data = i_stream_get_data(input, &size);
-	test_assert(size == strlen(output) && memcmp(data, output, size) == 0);
+	test_assert(size == strlen(output));
+	if (size > 0)
+		test_assert(memcmp(data, output, size) == 0);
 	i_stream_unref(&input);
 	i_stream_unref(&input_data);
 }

src/lib/test-istream-crlf.c

@@ -66,7 +66,9 @@ static void test_istream_crlf_input(const char *input)
 				test_assert(pos + (unsigned int)ret1 == size);
 				pos += ret1;
 			}
-			test_assert_idx(memcmp(data, str_data(output), size) == 0, j*10000+i);
+			if (size > 0)
+				test_assert_idx(memcmp(data, str_data(output),
+							size) == 0, j*10000+i);
 		}
 		test_assert_idx(size == str_len(output), j*10000+i);
 		i_stream_unref(&crlf_istream);