[Bug fortran/26682] New: gfortran fails with -fwhole-program optimization

[Bug fortran/26682] New: gfortran fails with -fwhole-program optimization

[jjcogliati-r1 at yahoo dot com]

The following simple.f90 program:
PROGRAM hello_world
  PRINT *,"Hello, World!"
END PROGRAM hello_world

does not compile with the following arguments:
gfortran -fwhole-program -O2 -o simple simple.f90

~/gcc_install/lib/gcc/i686-pc-linux-gnu/4.1.0/../../../libgfortranbegin.a(fmain.o)(.text+0x23):
In function `main':
../../../gcc-4.1.0/libgfortran/fmain.c:18: undefined reference to `MAIN__'
collect2: ld returned 1 exit status

The program compiles fine with just -O2 or -fwhole-program and prints out the
expected Hello, World!

I think the problem roughly is that -fwhole-program combined with -O2 is
optimizing out the main function since it is not getting called internally.

I was unable to find in the documentation any method of forcing external
visiblity in a fortran 90 program.  There was also no mention of gfortran not
having -fwhole-program working in
http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Optimize-Options.html


-- 
           Summary: gfortran fails with -fwhole-program optimization
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jjcogliati-r1 at yahoo dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26682

[Bug fortran/26682] gfortran fails with -fwhole-program optimization

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2006-03-14 15:19 -------
I have a fix already in mind for this simple issue.  Though -fwhole-program is
not going to be fixed for Fortran code until the front-end stops having more
than one decl per function.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |link-failure
   Last reconfirmed|0000-00-00 00:00:00         |2006-03-14 15:19:46
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26682

[Bug fortran/26682] gfortran fails with -fwhole-program optimization

[fxcoudert at gcc dot gnu dot org]

------- Comment #2 from fxcoudert at gcc dot gnu dot org  2007-10-01 10:58 -------
There are three different issues:

  1. -fwhole-program should be documented as not working for the Fortran
programs.

  2. The Fortran main program (MAIN__) needs to be kept by the -fwhole-program
optimization; I think one way of achieving this is to mark it as
"externally_visible", but I might be wrong (I've already been wrong on that
issue,!).

  3. We need to generate a correct call graph for Fortran code, either by
emitting one single decl per function, or by making the cgraph calculation
aware of this possible situation.

I'll try to tackle 1 and 2, but 3 needs to wait until 4.3 is branched.


-- 

fxcoudert at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |fxcoudert at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
           Keywords|                            |documentation
   Last reconfirmed|2007-07-13 15:47:54         |2007-10-01 10:58:25
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26682

[Bug fortran/26682] gfortran fails with -fwhole-program optimization

[fxcoudert at gcc dot gnu dot org]

------- Comment #3 from fxcoudert at gcc dot gnu dot org  2007-10-03 09:46 -------
Subject: Bug 26682

Author: fxcoudert
Date: Wed Oct  3 09:46:46 2007
New Revision: 128977

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128977
Log:
        PR fortran/26682

        * options.c (gfc_post_options): Issue an error when
        -fwhole-program is used.

        * doc/invoke.texi (-fwhole-program): Document that Fortran
        doesn't support this option.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/doc/invoke.texi
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/options.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26682

[Bug fortran/26682] gfortran fails with -fwhole-program optimization

[fxcoudert at gcc dot gnu dot org]

------- Comment #4 from fxcoudert at gcc dot gnu dot org  2007-10-03 21:27 -------
Subject: Bug 26682

Author: fxcoudert
Date: Wed Oct  3 21:27:39 2007
New Revision: 128993

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128993
Log:
        PR fortran/26682
        * trans-decl.c (build_function_decl): Set "externally_visible"
        attribute on the MAIN program decl.

Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/trans-decl.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26682

[Bug fortran/26682] gfortran fails with -fwhole-program optimization

[fxcoudert at gcc dot gnu dot org]

------- Comment #5 from fxcoudert at gcc dot gnu dot org  2007-10-03 21:30 -------
I've fixed 1 and 2 (and added an error message when -fwhole-program is used
with Fortran), and there is a separate PR to track 3, so I'll close this one.


-- 

fxcoudert at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26682