[Bug sanitizer/68099] New: arm-*-linux-gnueabihf -fsanitize=undefined warning: '<anonymous>' is used uninitialized in this function

["yba at tkos dot co.il" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68099

            Bug ID: 68099
           Summary: arm-*-linux-gnueabihf -fsanitize=undefined warning:
                    '<anonymous>' is used uninitialized in this function
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yba at tkos dot co.il
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org
  Target Milestone: ---

Created attachment 36586
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36586&action=edit
crosstool-ng .config file for arm-mxs-linux-gnueabihf

Command:
arm-mxs-linux-gnueabihf-g++ \
        -Wall -Wextra \
        -O3 \
        --sysroot=${STAGING} \
        -o test test.cpp

Code:
#include <iostream>

class Dog
{
public:

    typedef void(Dog::*BarkFunction)(int);
    Dog () {}

    void makeNoise (int z)
    {
        std::cout << "Woof!" << z << std::endl;
    }

    void something1()
    {
        BarkFunction fnc = &Dog::makeNoise;
        (this->*fnc)(7);
    }

    void something2();
};

void Dog::something2() {
        BarkFunction fnc = &Dog::makeNoise;
        (this->*fnc)(7);

        Dog::makeNoise(7);
}

int main(int argc, char* argv[])
{
    return 0;
}

Output:
dog.cpp:26:14: warning: '<anonymous>' is used uninitialized in this function
[-Wuninitialized]
  (this->*fnc)(7);
              ^

Comments:
1. crosstool-ng .config attached.

2. The warning cited is not emitted when the optimization -O<x> is removed from
the command.

3. The warning cited is not emitted on x86_64 compiler built with similar
config

4. Compiler was built using crosstool-ng using the attached .config.

5. Same problem happens with GCC 5.1.0 compiled with crosstool-ng with similar
arm-*-linux-gnuabihf .config