无法重现项目示例项目中的内存清理结果

Unable to reproduce memory sanitization results from the project's example project

本文关键字：项目 内存 结果      更新时间：2023-10-16

我从使用fedora rpm specfile从源代码构建的centos7，clang-3.6.1中得到了完全相同的结果。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。该页面上一次更新是在6个月前。

谷歌613版仍在使用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.

将谷歌测试更新为提示（746），并编译以下警告

➜ [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 并没有发现该页面中微不足道的建议案例

[==========] 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: ''
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，所以内存清理将非常有用。如果我做错了什么。谷歌测试似乎以某种方式抑制了这个错误。删除谷歌测试并将测试用例转换为

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

触发报告预期的明显错误

==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？

这不是MemoryManitizer或谷歌测试的问题：显然libc++最近发生了变化，现在它初始化了实际四字节字符串"foo"之外的字节，所以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，错误报告如预期：

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

结果在：

[==========] 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：当你配置谷歌测试以在613版本构建它时，你可以添加-DGTEST_USE_OWN_TR1_TUPLE=1来编译标志。

由于单元测试中看到的值是''，因此可能是字符串实际初始化了位置4处的内存，使其与C字符串（尾随零）兼容。单元测试和手动测试用例之间的差异可能是编译器优化的结果。如果将字符串切换为std::vector<char>{'f', 'o', 'o'}，会发生什么情况？

如果你也能发布单元测试代码，那会很有帮助。

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