[Bug c++/105976] New: -Wuse-after-free warning with std::shared_ptr<std::shared_ptr<T>[]>::reset

["anabelsmruggiero at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105976

            Bug ID: 105976
           Summary: -Wuse-after-free warning with
                    std::shared_ptr<std::shared_ptr<T>[]>::reset
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anabelsmruggiero at gmail dot com
  Target Milestone: ---

GCC 12.1 emits a use-after-free warning when calling
std::shared_ptr<std::shared_ptr<T>[]>::reset outside of main:


void testArrOfArr(){
    std::shared_ptr<std::shared_ptr< double[] >[]> testPtr; 
    testPtr.reset(new std::shared_ptr< double[] >[6]);
}

void testArr(){
    std::shared_ptr<std::shared_ptr< double >[]> testPtr; 
    testPtr.reset(new std::shared_ptr< double >[6]);
}

int main(){
    // Uncommenting the body of main squelches all warnings
    /*
    std::shared_ptr<std::shared_ptr< double >[]> testArrPtr;
    testArrPtr.reset(new std::shared_ptr< double >[6]);

    std::shared_ptr<std::shared_ptr< double[] >[]> testArrOfArrPtr;
    testArrOfArrPtr.reset(new std::shared_ptr< double[] >[6]);
    */
}

Compiler arguments: -std=c++20 -Wall -Wextra -O2 
This warning occurs at or above -02 and disappears below that.

I also have this repro on Godbolt with a few more additional lines that end up
squelching the warning: https://godbolt.org/z/YaKP985es