[RFA/libiberty] Enhance FILENAME_CMP for Windows filesystems

[Joel Brobecker <brobecker at adacore dot com>]

Hello,

We are using the FILENAME_CMP macro in GDB quite a bit, and it is
currently defined in include/filenames.h as:

    #define FILENAME_CMP(s1, s2)    strcasecmp(s1, s2)

This is for "DOSish" filesystems. For other filesystems, it's defined as
a straight strcmp:

    #define FILENAME_CMP(s1, s2)    strcmp(s1, s2)

I came across a case where the DWARF debug info unfortunately used '\'
as the directory separator in one case (in the .debug_info section),
while using '/' in another case (in the .debug_line section).

As a result, FILENAME_CMP returned that the following two files were
not equal:

        c:\cygwin\home\brobecke\tgdb\ex\\foo.adb
        c:/cygwin/home/brobecke/tgdb/ex//foo.adb

This causes the following problem in GDB, when we compile the unit
by giving GCC the full path name to the associated file, such as:

        % gcc -c -g c:\full\path\to\foo.adb

The GDB error looks like this:

        % gdb foo
        (gdb) b foo.adb:3
        No line 3 in file "c:\cygwin\home\brobecke\tgdb\ex\\foo.adb".


I propose to add a new filename_cmp function to libiberty:
  - On Unix, no change, it calls strcmp
  - On Windows, we make slash and backslash equal.

This is a modest improvement, since there are many other things we
can do to enhance it (such as normalizing the path so that '//' and '/'
are treated as equal for instance). But this paves the path for
further improvements of that sort. And in the meantime, if fixes
the problem we are facing.

For that, I added a new file, filename_cmp.c, updated the Makefile
to add this file to the list of required objects, and then changed
the FILENAME_CMP define to unconditionally call this new function.

libiberty/ change:
2007-03-28  Joel Brobecker  <brobecker@adacore.com>

        * filename_cmp.c: New file.
        * Makefile.in (CFILES): Add filename_cmp.c.
        (REQUIRED_OFILES): Add filename_cmp.o
        (filename_cmp.o): New rule.

include/ change:
2007-03-28  Joel Brobecker  <brobecker@adacore.com>

        * filenames.h (FILENAME_CMP): Adjust define to call filename_cmp
        regardless of the type of file system.

Tested on x86-linux and x86-windows, without any regression (using
the GDB testsuite).

OK to apply?

Thank you,
-- 
Joel

Attachment: filename_cmp.c
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Attachment: filename_cmp.diff
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