Bug#1055750: gfortran: [armhf] Yield SIGBUS when compiling with -fstack-clash-protection

[Rafael Laboissière]

The attached file bug-1055750.tgz contains a minimal code that triggers the bug on an armhf system : $ ./run ***** Compile without -fstack-clash-protection & run /usr/bin/ld: warning: /tmp/cc9l2GJa.o: requires executable stack (because the .note.GNU-stack section is executable) ***** Compile with -fstack-clash-protection & run /usr/bin/ld: warning: /tmp/ccP0miz5.o: requires executable stack (because the .note.GNU-stack section is executable)

    Program received signal SIGBUS: Access to an undefined portion of a memory 
object.

    Backtrace for this error:
    Bus error

* Rafael Laboissière <raf...@debian.org> [2023-11-10 15:52]:

Package: gfortran
Version: 13.2.0-1
Severity: normal

Dear Maintainer,







   $ ./gfortran-stack-clash-protection-armhf-bug.sh
   […]
   Program received signal SIGBUS: Access to an undefined portion of a memory 
object.

   Backtrace for this error:
   Bus error





   $ gdb x09f
   […]
   (gdb) run -dev ps -o /dev/null
   Starting program: /home/rafael/fortran/x09f -dev ps -o /dev/null
   [Thread debugging using libthread_db enabled]
   Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".

   Program received signal SIGBUS, Bus error.
   0x00400dfe in x09f::mypltr (x=0, y=1, xt=1, yt=34) at x09f.f90:193
   193             xt = tr(1) * x + tr(2) * y + tr(3)



Any help will be appreciated.

Best,

Rafael Laboissière

The motivation for the present bug report comes from Bug#1055228. Since version 1.22.1 of dpkg-dev was released (on October 30), the plplot package FTBFS due to a failing compilation of one of Fortran examples, which is exercised as a unit test during package building. The package built fine previously. The problem is triggered by the change in dpkg-buildflags, which now includes -fstack-clash-protection in FFLAGS. I am attaching to this bug message a shell script that can reliably trigger the bug on an armhf system. Here is the output: Note that the bug does not happen on amd64. Also, it does not happen on armhf when the option -fstack-clash-protection is not used in the invocation of gfortran. As far as I can tell, the problem is due to a global variable (tr) that is not correctly accessed in a private function (mypltr) of the x09f program. Here is what gdb tells me: My knowledge of Fortran and gfortran is way too scarce and, therefore, I cannot debug the problem deeper. There may be a programming error in x09f.f90 or this may be a problem with gfortran on armhf when option -fstack-clash-protection is given.

bug-1055750.tgz
Description: application/gtar-compressed