Re: [PATCH 3/3] gdb/corelow.c: do not try to reopen a file if open failed once

[Andrew Burgess <aburgess@redhat.com>]

Lancelot SIX via Gdb-patches <gdb-patches@sourceware.org> writes:

> In the current implementation, core_target::build_file_mappings will try
> to locate and open files which were mapped in the process for which the
> core dump was produced.  If the file cannot be found or cannot be
> opened, GDB will re-try to open it once for each time it was mapped in
> the process's address space.
>
> This patch makes it so GDB recognizes that it has already failed to open
> a given file once and does not re-try the process for each mapping.

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

> ---
>  gdb/corelow.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/gdb/corelow.c b/gdb/corelow.c
> index ce68f91132e..b831a90792c 100644
> --- a/gdb/corelow.c
> +++ b/gdb/corelow.c
> @@ -233,6 +233,16 @@ core_target::build_file_mappings ()
>  	   weed out non-file-backed mappings.  */
>  	gdb_assert (filename != nullptr);
>  
> +	if (unavailable_paths.find (filename) != unavailable_paths.end ())
> +	  {
> +	    /* We have already seen some mapping for FILENAME but failed to
> +	       find/open the file.  There is no point in trying the same
> +	       thing again so just record that the range [start, end) is
> +	       unavailable.  */
> +	    m_core_unavailable_mappings.emplace_back (start, end - start);
> +	    return;
> +	  }
> +
>  	struct bfd *bfd = bfd_map[filename];
>  	if (bfd == nullptr)
>  	  {
> @@ -250,11 +260,10 @@ core_target::build_file_mappings ()
>  	    if (expanded_fname == nullptr)
>  	      {
>  		m_core_unavailable_mappings.emplace_back (start, end - start);
> -		/* Print just one warning per path.  */
> -		if (unavailable_paths.insert (filename).second)
> -		  warning (_("Can't open file %s during file-backed mapping "
> -			     "note processing"),
> -			   filename);
> +		unavailable_paths.insert (filename);
> +		warning (_("Can't open file %s during file-backed mapping "
> +			   "note processing"),
> +			 filename);
>  		return;
>  	      }
>  
> @@ -264,10 +273,10 @@ core_target::build_file_mappings ()
>  	    if (bfd == nullptr || !bfd_check_format (bfd, bfd_object))
>  	      {
>  		m_core_unavailable_mappings.emplace_back (start, end - start);
> -		if (unavailable_paths.insert (filename).second)
> -		  warning (_("Can't open file %s which was expanded to %s "
> -			     "during file-backed mapping note processing"),
> -			   filename, expanded_fname.get ());
> +		unavailable_paths.insert (filename);
> +		warning (_("Can't open file %s which was expanded to %s "
> +			   "during file-backed mapping note processing"),
> +			 filename, expanded_fname.get ());
>  
>  		if (bfd != nullptr)
>  		  {
> -- 
> 2.34.1