[Bug c++/112350] New: gcc is not triggering a dangling reference indicating stack use after return

[Bug c++/112350] New: gcc is not triggering a dangling reference indicating stack use after return

[mohamed.selim at dxc dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112350

            Bug ID: 112350
           Summary: gcc is not triggering a dangling reference indicating
                    stack use after return
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mohamed.selim at dxc dot com
  Target Milestone: ---

Scenario A:
gcc is not triggering a dangling reference indicating stack use after return,
the address-sanitizer does trigger though.

"==1==ERROR: AddressSanitizer: stack-use-after-return on"

Scenario B:
gcc triggers a warning "-Wreturn-local-addr"

The sanitizers intervenes in both scenarios as expected, while gcc warnings in
not triggered in scenario A. Looks like the reference_wrapper has something to
do with it.


compiler options used:
-std=c++14 -Wframe-address -Wreturn-local-addr -Wall -Wextra -Wpedantic
-fsanitize=address


#include <iostream>
#include <utility>


// scenario A
const int& foo()
{
    int x = 234;
    std::reference_wrapper<int> s{x};

    return s.get();
}

// scenario B
const int& foo()
{
    int s = 234;   
    return s;
}

int main()
{
    const auto& f_res = foo();
    std::cout << "result: " << f_res << "\n";

    return 0;
}

[Bug c++/112350] gcc is not triggering a dangling reference indicating stack use after return

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112350

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
With optimization enabled and without -fsanitize=address  we get:

<source>: In function 'const int& foo1()':
<source>:12:18: warning: using a dangling pointer to 'x' [-Wdangling-pointer=]
   12 |     return s.get();
      |                  ^
<source>:9:9: note: 'x' declared here
    9 |     int x = 234;
      |         ^

[Bug c++/112350] gcc is not triggering a dangling reference indicating stack use after return with -fsanitize=address and optimization

[mohamed.selim at dxc dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112350

--- Comment #2 from Mohamed <mohamed.selim at dxc dot com> ---
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112350&GoAheadAndLogIn=1

it's shown here that the warning is triggered by setting -O3 optimization level
to 3. 
I don't know if such behavior is expected i.e. triggering warning is coupled
with optimization level!!!

So the above link to compiler explorer example shows only the diagnostic error
from the sanitizer, if -O3 is added the warning is triggered.