In file included from external/gtest/src/../include/gtest/gtest-param-test.h:157:0, from external/gtest/src/../include/gtest/gtest.h:69, from external/gtest/src/gtest_main.cc:32:external/gtest/src/../include/gtest/internal/gtest-param-util.h:122:11: error: ‘ptrdiff_t’ does not name a typeIn file included from external/gtest/src/../include/gtest/gtest-param-test.h:157:0, from external/gtest/src/../include/gtest/gtest.h:69, from external/gtest/src/../src/gtest.cc:34, from external/gtest/src/gtest-all.cc:36:external/gtest/src/../include/gtest/internal/gtest-param-util.h:122:11: error: ‘ptrdiff_t’ does not name a typeIn file included from external/gtest/src/gtest-all.cc:38:0:解决方法：$vi external/gtest/src/../include/gtest/internal/gtest-param-util.h#include <cstddef>
