[Bug fortran/54852] New: Bogus(?) warnings when compiling gfortran.dg/bind_c_vars.f90 gfortran.dg/bind_c_vars_driver.c with -flto

[Bug fortran/54852] New: Bogus(?) warnings when compiling gfortran.dg/bind_c_vars.f90 gfortran.dg/bind_c_vars_driver.c with -flto

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54852

             Bug #: 54852
           Summary: Bogus(?) warnings when compiling
                    gfortran.dg/bind_c_vars.f90
                    gfortran.dg/bind_c_vars_driver.c with -flto
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dominiq@lps.ens.fr


When compiling gfortran.dg/bind_c_vars.f90 gfortran.dg/bind_c_vars_driver.c
with -flto, one gets the following warnings which seem bogus:

[macbook] f90/bug% /opt/gcc/gcc4.8a/bin/gfortran -flto
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars.f90
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars_driver.c
In file included from
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars.f90:16:0,
                 from :0:
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars_driver.c:12:5: warning:
type of 'myF90Array2D' does not match original declaration [enabled by default]
 int myF90Array2D[2][3];      /* B in bind_c_vars */
     ^
In file included from :0:0:
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars.f90:16:0: note: previously
declared here
   integer(c_int), bind(c, name="myF90Array2D") :: B(3, 2)
 ^
In file included from
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars.f90:16:0,
                 from :0:
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars_driver.c:11:5: warning:
type of 'myF90Array3D' does not match original declaration [enabled by default]
 int myF90Array3D[10][5][18]; /* A in bind_c_vars */
     ^
In file included from :0:0:
/opt/gcc/work/gcc/testsuite/gfortran.dg/bind_c_vars.f90:15:0: note: previously
declared here
   integer(c_int), bind(c, name="myF90Array3D") :: A(18, 3:7, 10)
 ^

The executable runs fine.

[Bug fortran/54852] Bogus(?) warnings when compiling gfortran.dg/bind_c_vars.f90 gfortran.dg/bind_c_vars_driver.c with -flto

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54852

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2013-06-29
                 CC|                            |jh at suse dot cz
     Ever confirmed|0                           |1

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Still present at revision 200557.

[Bug fortran/54852] Bogus(?) warnings when compiling gfortran.dg/bind_c_vars.f90 gfortran.dg/bind_c_vars_driver.c with -flto

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54852

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu.org

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
*** Bug 60057 has been marked as a duplicate of this bug. ***

[Bug fortran/54852] Bogus(?) warnings when compiling gfortran.dg/bind_c_vars.f90 gfortran.dg/bind_c_vars_driver.c with -flto

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54852

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic, lto
             Status|WAITING                     |NEW

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
LTO warns that

/space/rguenther/src/svn/trunk/gcc/testsuite/gfortran.dg/bind_c_vars_driver.c:12:5:
warning: type of 'myF90Array2D' does not match original declaration [enabled by
default]
/space/rguenther/src/svn/trunk/gcc/testsuite/gfortran.dg/bind_c_vars.f90:16:0:
note: previously declared here
/space/rguenther/src/svn/trunk/gcc/testsuite/gfortran.dg/bind_c_vars_driver.c:11:5:
warning: type of 'myF90Array3D' does not match original declaration [enabled by
default]
/space/rguenther/src/svn/trunk/gcc/testsuite/gfortran.dg/bind_c_vars.f90:15:0:
note: previously declared here

which effectively means that assignments in GIMPLE between those arrays
would be invalid (not array members but whole arrays).  Not sure if we
can create a testcase that will eventually ICE though.  Usually the above
also means that the arrays use different alias sets but that's safe here
because the alias set of an array is that of its element (and those are
compatible here).

The issue is that in C a[2][3] is ARRAY_TYPE <ARRAY_TYPE <...> > but
GFortran represents a(2)(3) as 1D ARRAY_TYPE <...> and thus both types
are not structurally equivalent (which is why LTO warns).

Not sure if this case is motivation enough to treat arrays structurally
the same if their overall size is the same.