Re: gdb_realpath: dealing with ./ and ../

[Daniel Jacobowitz <drow at false dot org>]

On Thu, Jan 03, 2008 at 10:20:19AM -0500, Aleksandar Ristovski wrote:
> Hello,
> 
> First a question, to give an idea what I am talking about and then detailed
> explanation.
> 
> Question: Should gdb_realpath deal with './' and '../' path elements and
> compact them along with 'canonicalization' it already does?

The problem with this idea is that removing ../ is not reliably
correct.  On Unix, symlinks allow foo/../bar and bar to be different
directories.  We should only canonicalize paths to local files, not to
files mentioned in debug information.

gdb_realpath shouldn't need any changes to handle ..; it works from
the local filesystem and constructs a real canonical path.  I see that
you're on Windows.  gdb_realpath may not handle Windows correctly;
libiberty's lrealpath does and I don't know why we still have both.

> When our cross-compiler generates binary, it stores relative path in
> .debug_line section (relative to compilation dir), i.e. '..'.

What's in .debug_info?  Also, what version of GDB?

> It loads line table, finds '..', constructs absolute path using compilation
> directory and creates "C:/foo/bar/Debug/../main.cc" and then compares this
> (using FILENAME_CMP macro) to existing subfile-s and fails to find it (file
> buildsym.c, function start_subfile).

I have:

 <0><154>: Abbrev Number: 1 (DW_TAG_compile_unit)
  <189>     DW_AT_name        : ../main.c
  <193>     DW_AT_comp_dir    : /home/drow/z/baz

 The Directory Table:
  ..

 The File Name Table:
  Entry Dir     Time    Size    Name
  1     1       0       0       main.c

So everything constructs the same /home/drow/z/baz/../main.c.

-- 
Daniel Jacobowitz
CodeSourcery