[Bug fortran/87689] Memory corruption on Power 8

tkoenig at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Tue Oct 23 22:16:00 GMT 2018


Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
             Status|WAITING                     |NEW

--- Comment #3 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
I checked, and it seems that this is an old bug; it occurs both
with gfortran 4.8.5 and 8.1.0.

This goes away with -flto or if you put both procedures into one file,
and does not happen on Linux.

Tree dump looks reasonable with 8.1:

    static integer(kind=4) C.2183 = 1;
    static integer(kind=4) C.2184 = 2;
    static integer(kind=4) C.2185 = 3;
    static integer(kind=4) C.2186 = 4;
    static integer(kind=4) C.2187 = 5;
    static integer(kind=4) C.2188 = 6;
    character(kind=1) str.0[20];

    doesntwork_p8 ((character(kind=1)[1:20] *) &str.0, 20, &c, &C.2183,
&C.2184, &C.2185, &C.2186, &C.2187, &C.2188, 1);
    __builtin_memmove ((void *) &res, (void *) &str.0, 20);


doesntwork_p8 (character(kind=1)[1:20] & __result, integer(kind=8) .__result,
character(kind=1)[1:1] & restrict c, integer(kind=4) & restrict a1,
integer(kind=4) & restrict a2, integer(kind=4) & restrict a3, integer(kind=4) &
restrict a4, integer(kind=4) & restrict a5, integer(kind=4) & restrict a6,
integer(kind=8) _c)

What looks less reasonable is the debug output:

breakpoint 1, doesntwork_p8 (__result=@0x3fffffffed80:
.__result=20, c='`', a1=1, a2=2, a3=3, a4=4, a5=5, 
    a6=<error reading variable: Cannot access memory at address 0x0>, _c=0) at

This looks like the arguments pushed on the stack somehow have the wrong number
of bytes...

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