<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/151952>151952</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Msan]False positive reported of std::__1::basic_istream<char, std::__1::char_traits<char>>& std::__1::getline
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          zhaojiangkun-1
      </td>
    </tr>
</table>

<pre>
    When I use getline, there are some warnings even though it's initialized.
Is this a false positive behavior of getline?
```#include <iostream>
#include <string>
class A
{
public:
    A () {}
    ~A() {}
    void func1() noexcept;
};

void A::func1() noexcept
{
    std::string str = "heloworld";
    getline(std::cin, str, '\n');
    std::cout << str << std::endl;
}

int main() {
    A a {};
    a.func1();
    return 0;
}
```
Compiler version：
```
clang version 15.0.4
Target: aarch64-unknown-linux-gnu
Thread model: posix
```
```
[root@xxxxx]# ./msan-run
==3544==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0xaaaab0ade4b4 in std::__1::basic_istream<char, std::__1::char_traits<char>>& std::__1::getline<char, std::__1::char_traits<char>, std::__1::allocator<char>>(std::__1::basic_istream<char, std::__1::char_traits<char>>&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&, char) /xxxxx/usr/include/c++/v1/istream:1507:9
    #1 0xaaaab0ade024 in A::func1() /home/ci/workspace/tmp-warning/test.cpp:14:5
    #2 0xaaaab0ade164 in main /home/ci/workspace/tmp-warning/test.cpp:20:7
    #3 0xe7fbe5a2ae6c  (/usr/lib64/libc.so.6+0x2ae6c)
    #4 0xe7fbe5a2af48 in __libc_start_main (/usr/lib64/libc.so.6+0x2af48)
    #5 0xaaaab0a5b52c in _start /xxxx/aarch64-aos-linux/glibc/2.34-AOS4.0/glibc-2.34/csu/../sysdeps/aarch64/start.S:81

SUMMARY: MemorySanitizer: use-of-uninitialized-value /xxxx/usr/include/c++/v1/istream:1507:9 in std::__1::basic_istream<char, std::__1::char_traits<char>>& std::__1::getline<char, std::__1::char_traits<char>, std::__1::allocator<char>>(std::__1::basic_istream<char, std::__1::char_traits<char>>&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&, char)
==3544==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0xaaaab0adf534 in std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::clear[abi:v15004]() /xxxxxxx/usr/include/c++/v1/string:3328:9
    #1 0xaaaab0ade4e8 in std::__1::basic_istream<char, std::__1::char_traits<char>>& std::__1::getline<char, std::__1::char_traits<char>, std::__1::allocator<char>>(std::__1::basic_istream<char, std::__1::char_traits<char>>&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&, char) /xxxxxxx/usr/include/c++/v1/istream:1513:19
    #2 0xaaaab0ade024 in A::func1() /home/ci/workspace/tmp-warning/test.cpp:14:5
    #3 0xaaaab0ade164 in main /home/ci/workspace/tmp-warning/test.cpp:20:7
    #4 0xe7fbe5a2ae6c  (/usr/lib64/libc.so.6+0x2ae6c)
    #5 0xe7fbe5a2af48 in __libc_start_main (/usr/lib64/libc.so.6+0x2af48)
    #6 0xaaaab0a5b52c in _start /xxxxxx/aarch64-aos-linux/glibc/2.34-AOS4.0/glibc-2.34/csu/../sysdeps/aarch64/start.S:81

SUMMARY: MemorySanitizer: use-of-uninitialized-value /xxxxx/usr/include/c++/v1/string:3328:9 in std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::clear[abi:v15004]()
hello
==3544==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0xaaaab0ae106c in std::__1::basic_ostream<char, std::__1::char_traits<char>>& std::__1::__put_character_sequence<char, std::__1::char_traits<char>>(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, char const*, unsigned long) /xxxxx/usr/include/c++/v1/ostream:760:13
    #1 0xaaaab0adeed0 in std::__1::basic_ostream<char, std::__1::char_traits<char>>& std::__1::operator<<<char, std::__1::char_traits<char>, std::__1::allocator<char>>(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&) /xxxxx/usr/include/c++/v1/ostream:1086:12
    #2 0xaaaab0ade060 in A::func1() /home/ci/workspace/tmp-warning/test.cpp:15:15
    #3 0xaaaab0ade164 in main /home/ci/workspace/tmp-warning/test.cpp:20:7
    #4 0xe7fbe5a2ae6c  (/usr/lib64/libc.so.6+0x2ae6c)
    #5 0xe7fbe5a2af48 in __libc_start_main (/usr/lib64/libc.so.6+0x2af48)
    #6 0xaaaab0a5b52c in _start /xxxxxx/aarch64-aos-linux/glibc/2.34-AOS4.0/glibc-2.34/csu/../sysdeps/aarch64/start.S:81

SUMMARY: MemorySanitizer: use-of-uninitialized-value /xxxxxx/usr/include/c++/v1/ostream:760:13 in std::__1::basic_ostream<char, std::__1::char_traits<char>>& std::__1::__put_character_sequence<char, std::__1::char_traits<char>>(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, char const*, unsigned long)
hello
MemorySanitizer: 3 warnings reported.

```

</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzsWU1v2zgT_jX0hbBAkaItH3yQ4-pFD-kLNLso9mRQ0thiS5NaknLSHva3L6gP2wnSdJNNWmSRQAjl4fAZfsw8DyQJ5-ROAywRXyG-nojW18Yuv9XCfJZC7760ehpPClN9XX6qQeP3uHWAd-CV1IDoBfY1WMDCAnZmD_haWC31zmE4gMa-Nu2uxtIjOndYaumlUPIbVBEi2XuHfS0dFngrlAPcGCe9PAAuoBYHaSw222MkliOSoRkZLsqkLlVbAUbsQhrnLYg9Yu-C060-563Uu76nVMI5nAWf-QqRrGkLJUvEggVjjDOMaIroAofu-Xqw_pXdZz0YWeFtq8t46NUGbkpoPGKrLsB6uCFZ55qFMCy7d8Q4n4DrfNV79hPHzluM2BojSmtQ5tpYVSFKe_Aw4HgU6XFoKXU4GedtaBCdI36hQ0MXp3Enb9P6sFOIXQzRhtuhH3SlTovqViS1x3sRohw3ZtxBMW7TMZCIzhZ9MlvwrdWY3II-ni_JLsy-kQosPoB10mj0LkerC7TI7viVSujd6IRjHpEoQST7TdgdeMQyLIQt61kybfUXba71VEnd3kx3ug1etQVR4b2pQAXfkII3dwLcuucra4xHCbkJf4ivEWU4QjTfO6GnttXBia0RWzOeJP3dp-zjh_cf_hfwL2Fv7NcrEQrhG9hgah1MzXba6rPqmB6EamHYKEQZweRGCCEKIipIigRLfTqfzSbubwrhZLmRYy1clLWwfR7c9Qw9G2-F9G70Y-_CRWf3eB9L8NGI97oKpUwpvLF3QqcvtKL7B_TQIzu87Mq6KfQRFhjRvM8dmrfOIpoPZIVoXiK66q78EIeOcd1ZzMkcsWxxyoj4PCMI7TLiHopBNK_NvsOWiObXxn5xjSiDwe-b6UDW4Rc4H5VNE4IliGX8FIqeh4pnXahQ_E8CpwSxbH4CZ5jcwHxbABdUwKzEPQUPW6NkMUv6toyciWaIrshN5xi45IiSnKNskzRMcbMJozbOC-s3w3x_jLxN0lvI_LR4XnBadsgd5niQiOYjwwjjenZBNN8FZERzGrFkmv3_KonIaJ0GW9g11yKaR4E93FdXQeNOWMEWokRXiGVp3NPu1e-Xl9nHPx5NJGdTfXTKvVHNq6WaF5eiLWcPStFPWXIPo0BYxFeikIhlh5gTknTinJ5T7j-pgHHOGWM0fYBzE0jfSuPVlsajUuKcFGMWmsV31PFlhZi9pBAnzyLE_MWEePZDIX5VUvwUJnoFVItIVoNS5qWlB2IyKx_aD_Ps_LvZNK3fBC9RerAbB3-2oMunEPKDPPsvZz6SHC6Ndh7RLBha3b3kqbAygQce8xBynE42nwXKiNl3BBEq8nMPxDRghxztr1-ji89wXr-yqMc8mT01LWKSzkJDv6eJM_Kcmsj7f2-i-F8UxSfx0ZsMPFUGztT6nvNip3f5Fhpjff_W_s4b0Um1ZNWCLcQElvGcJywmKZ9N6mXKeQnJQjASFzGDIpnDfMt5AdsUyLaqJnJJCeUkJUlMWRIn0ZwstvGC0YRQKItigRICeyFVpNRhHxm7m0jnWljGPF5wOlGiAOW67xaUarjGXS-iFPH1xC7DoGnR7hxKiJLOuxOMl151HzwundCIr_Pbnx_G1WKz_fnPd5PWqmXtfeOCmeahKKWv2yIqzT5QgjqMzbSx5jOUvntEcS2E8hz25rCkfwcAAP__zkqtPA">