error: ‘ptrdiff_t’ does not name a type

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 type
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/../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 type
In 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>