c++ - 无法从项目的示例项目中重现内存清理结果

Question

我从 centos7、clang-3.6.1 中得到了完全相同的结果，这些结果是使用 fedora rpm 规范文件从源代码构建的。 Ubuntu 14.04，clang-3.4

使用此处 wiki 中的说明 https://github.com/google/sanitizers/wiki/MemorySanitizerLibcxxHowTo 尽可能接近。该页面最后一次更新是在 6 个月前。

googlest 修订版 613 仍在使用 tr1

In file included from /home/hal/googletest/src/gtest-all.cc:39:
In file included from /home/hal/googletest/include/gtest/gtest.h:58:
In file included from /home/hal/googletest/include/gtest/internal/gtest-internal.h:40:
/home/hal/googletest/include/gtest/internal/gtest-port.h:507:13: fatal error: 
      'tr1/tuple' file not found
#   include <tr1/tuple>  // NOLINT
            ^
1 error generated.

将 googletest 更新为提示 (746) 并编译时出现以下警告

➜ [hal@davis 9:54 ~/gtest-msan] make
Scanning dependencies of target gtest
[ 50%] Building CXX object CMakeFiles/gtest.dir/src/gtest-all.cc.o
clang: warning: -lc++abi: 'linker' input unused
clang: warning: -lc++abi: 'linker' input unused
clang: warning: argument unused during compilation: '-L/home/hal/libcxx_msan/lib'
clang: warning: argument unused during compilation: '-L/home/hal/libcxx_msan/lib'
Linking CXX static library libgtest.a

msan 没有采纳该页面中建议的琐碎案例

[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from FooTest
[ RUN      ] FooTest.Foo
test.cc:7: Failure
Value of: foo[4]
  Actual: '\0'
Expected: 'z'
Which is: 'z' (122, 0x7A)
[  FAILED  ] FooTest.Foo (1 ms)
[----------] 1 test from FooTest (1 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (1 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] FooTest.Foo

 1 FAILED TEST

我有一个项目，其中 valgrind barfs 由于使用了一些非常大的 mmap，因此内存清理非常有用。如果我做错了什么。看来 googletest 以某种方式抑制了错误。删除谷歌测试并将测试用例转换为

if(foo[4] == 'z') std::cout << "它是 z"<< std::endl;

按预期触发明显错误的报告

==29128== WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x7f59270c1738 in std::string::_Rep::_M_is_leaked() const /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/basic_string.h:192:18
    #1 0x7f59270c1738 in std::string::_M_leak() /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/basic_string.h:316
    #2 0x7f59270c1738 in std::string::operator[](unsigned long) /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/basic_string.h:849
    #3 0x7f59270c1738 in main /home/hal/test-gtest-msan/test2.cc:7
    #4 0x7f5925c2bb14 in __libc_start_main (/lib64/libc.so.6+0x21b14)
    #5 0x7f592706ce30 in _start (/home/hal/test-gtest-msan/test2+0x35e30)

  Uninitialized value was created by an allocation of 'foo' in the stack frame of function 'main'
    #0 0x7f59270c12e0 in main /home/hal/test-gtest-msan/test2.cc:4

SUMMARY: MemorySanitizer: use-of-uninitialized-value /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/basic_string.h:192 std::string::_Rep::_M_is_leaked() const
Exiting

是否可以将内存清理与单元测试库一起使用？

Answer 1

这不是 MemorySanitizer 或 googletest 问题:显然 libc++ 最近发生了变化，现在它初始化实际的四字节字符串“foo”之外的字节，因此 MSan 不会为这种越界访问生成报告。

MSan wiki 已更新为使用不同的示例，如预期的那样报告错误:

TEST(FooTest, Foo) {
  int uninitialized;
  EXPECT_GT(uninitialized, 5);
}

结果:

[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from FooTest
[ RUN      ] FooTest.Foo
==39032== WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x48d73c in testing::AssertionResult testing::internal::CmpHelperGT<int, int>(char const*, char const*, int const&, int const&) googletest/include/gtest/gtest.h:1463:1
    #1 0x48ce7a in FooTest_Foo_Test::TestBody() test.cc:6:3
...

附言当您配置 googletest 以在修订版 613 构建它时，您可以添加 -DGTEST_USE_OWN_TR1_TUPLE=1 来编译标志。