title: tracebackqq() with ifort leads to segmentation fault
body: <p>Why does the following code lead to segmentation fault when compiled with <code>ifort</code>?</p>
  <pre><code>! testtrb.f90
  program testtrb
      call tracebackqq()  ! This is for ifort
      !call backtrace()  ! This is for gfortran 
      print '(/1A/)', 'Finish.'
  end program testtrb
  </code></pre>
  <p>Executing
  <code>ifort testtrb.f90 ; ./a.out</code>,
  I got</p>
  <pre><code>forrtl: severe (174): SIGSEGV, segmentation fault occurred
  Image              PC                Routine            Line        Source             
  a.out              0000000000409FFA  Unknown               Unknown  Unknown
  libpthread-2.31.s  00007F6E2C9903C0  Unknown               Unknown  Unknown
  a.out              000000000040746D  Unknown               Unknown  Unknown
  a.out              000000000040383B  Unknown               Unknown  Unknown
  a.out              00000000004037E2  Unknown               Unknown  Unknown
  libc-2.31.so       00007F6E2C7B00B3  __libc_start_main     Unknown  Unknown
  a.out              00000000004036EE  Unknown               Unknown  Unknown
  </code></pre>
  <p>The return of <code>ifort --version</code> is <code>ifort (IFORT) 19.1.1.217 20200306</code>. I also tried
  <code>ifort (IFORT) 2021.1 Beta 20201112</code>, the result being similar. The value of <code>uname -r</code> is <code>5.9.0-050900-generic</code>, if it is helpful.</p>
  <p>However, changing <code>tracebackqq</code> to <code>backtrace</code> and runing <code>gfortran testtrb.f90 ; ./a.out </code>, I get</p>
  <pre><code>#0  0x7f789588ad3a
  #1  0x557b8f35119d
  #2  0x557b8f351254
  #3  0x7f789569f0b2
  #4  0x557b8f3510cd
  #5  0xffffffffffffffff
  
  Finish.
  </code></pre>
  <p>This seems correct.</p>
  <p>So why does <code>tracebackqq</code> give rise to SIGSEGV?</p>
  <p>Any comments or criticism will be appreciated. Thanks.</p>