Re: [PATCH] gdb/solib-rocm: add support for file URI on Windows

[Pedro Alves <pedro@palves.net>]

On 2026-05-20 18:22, Lancelot SIX wrote:

> Current GDB does not really AMDGPU debugging on Windows (there are still

Some word missing, I guess "support".

> a couple of missing necessary pieces), but this patch can still be
> applied upstream and will eventually be needed.  I have tested this
> patch on top of the downstream ROCgdb windows branch[1].  I have also
> tested this patch on Linux + gfx1031 on top of master to ensure this
> causes no regression.
> 
> [1] https://github.com/ROCm/ROCgdb/tree/amd-temp-windows
> ---
>  gdb/solib-rocm.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/gdb/solib-rocm.c b/gdb/solib-rocm.c
> index d9ae4294c98..d8d36d2f3c0 100644
> --- a/gdb/solib-rocm.c
> +++ b/gdb/solib-rocm.c
> @@ -30,6 +30,7 @@
>  #include "solib.h"
>  #include "solib-svr4.h"
>  #include "symfile.h"
> +#include "filesystem.h"
>  
>  namespace {
>  
> @@ -586,6 +587,21 @@ rocm_bfd_iovec_open (bfd *abfd, inferior *inferior)
>  
>        if (protocol == "file")
>  	{
> +	  /* Windows absolute file path can be encoded with a leading "/" in
> +	     the URI: "file:///C:/Users/foo/bar".  This scheme is not strictly
> +	     standard but widely used (see RFC 8089 Appendix E.2).  


I think this comment has it backwards.  "file:///C:/Users/foo/bar" is actually the standard
form per RFC 8089.  It's the regular "file://<auth>/<path>" syntax where the authority is
empty and the path-absolute happens to begin with a drive letter, so you get a
leading / before "C:".

The non-standard short form discussed by RFC 8089 Appendix E.2 is:

 file:c:/path/to/file

... with no "//" and no leading slash before the drive.

That same appendix states:

 'URIs of the form "file:///c:/path/to/file" are already supported by the "path-absolute" rule.'

These are standard.

The code is still correct, though.  Once you decode the standard URI you do get "/C:/Users/foo/bar",
and you do need to strip the leading / on DOS-based filesystems to turn it back into a real
Windows path.  That's just an artifact of the URI grammar requiring a path-absolute (must
start with /).  See RFC 8089 Appendix D.2.  It's not because the URI form is non-standard.

I'd suggest rewording the comment to something like:

  /* A Windows absolute file path is encoded in a file: URI with a leading
     "/" before the drive letter: "file:///C:/Users/foo/bar".  See grammar in
     RFC 8089 Section 2, the path-absolute production requires the leading "/".
     'path-absolute' is defined by RFC 3986 Section 3.3.
     After decoding, decoded_path would be "/C:/Users/foo/bar", which is not a
     valid Windows path.  Drop the leading "/" as a normalization step.  */

Otherwise LGTM.

Approved-By: Pedro Alves <pedro@palves.net>

Thanks,
Pedro Alves