Re: Problems while debugging fortran

[Daniel Jacobowitz <drow@false.org>]

On Thu, Sep 20, 2007 at 01:46:22PM -0700, Joel Brobecker wrote:
> > No, just "break <linenumber>". However, I tried your command and it
> > worked. Why? Shouldn't the behavior be the same in both cases?
> 
> It should be the same if the "current file" is set to test.f.
> It looks like it isn't. For some reason, GDB thinks that the current
> file is something else. Again, perhaps a copy of your GDB session
> might give a clue.

Here's a relevant patch from the Debian packages of GDB.  As you can
see it comes from a mailing list message - I don't remember exactly
who submitted it without looking it up and I don't remember exactly
why it was never committed, but it was probably Wu Zhou and it was
probably never merged because of the larger issue of symbol case
sensitivity.

-- 
Daniel Jacobowitz
CodeSourcery

Daniel,

Although the proper way of adding case insensitivity to symbol lookup is 
still under discussion, I think it might be desirable to set the main 
function of Fortran programs to "MAIN__" first.  Because it can at least 
let GDB recognize that the language is Fortran after loading a Fortran 
executable only.  What is your idea on this?  Please comments.  TIA!

Here is the patch to set the main function in Fortran programs to 
"MAIN__".  And followed is a patch to verify this.  Tested with g77 and 
gfortran on x86, and g77 on ppc64.  With the first patch, it reported 
PASS; without, report FAIL.  No regression is found in gdb.fortran 
testcases.  

P.S: if there is a symbol named "MAIN__" in sources of other languages, it 
might disturb the debugging.  But I am not sure how much it is.

---
 gdb/symtab.c                       |    8 +++++--
 gdb/testsuite/gdb.fortran/lang.exp |   40 +++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 2 deletions(-)

Index: gdb/symtab.c
===================================================================
--- gdb/symtab.c.orig	2007-01-27 20:35:18.000000000 -0500
+++ gdb/symtab.c	2007-01-27 20:35:34.000000000 -0500
@@ -4189,8 +4189,12 @@ find_main_name (void)
     }
 
   /* The languages above didn't identify the name of the main procedure.
-     Fallback to "main".  */
-  set_main_name ("main");
+     Fallback to "MAIN__" (g77 and gfortran) if we can find it in the 
+     minimal symtab, to "main" otherwise.  */
+  if (lookup_minimal_symbol ("MAIN__", NULL, NULL))
+    set_main_name ("MAIN__");
+  else
+    set_main_name ("main");
 }
 
 char *
Index: gdb/testsuite/gdb.fortran/lang.exp
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gdb/testsuite/gdb.fortran/lang.exp	2007-01-27 20:35:34.000000000 -0500
@@ -0,0 +1,40 @@
+# Copyright 2005 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
+
+# This file was written by Wu Zhou. (woodzltc@cn.ibm.com)
+
+# This file is part of the gdb testsuite.  It is intended to test that gdb
+# could recognize the Fortran language after loading the binary
+
+if $tracelevel then {
+	strace $tracelevel
+}
+
+set testfile "array-element"
+set srcfile ${srcdir}/${subdir}/${testfile}.f
+set binfile ${objdir}/${subdir}/${testfile}
+
+if  { [gdb_compile "${srcfile}" "${binfile}" executable {debug f77}] != "" } {
+    untested "Couldn't compile ${srcfile}"
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+gdb_test "show language" ".*currently fortran.*" "show language(fortran)"