[7/9] Update exec_file_attach to cope with "target:" filenames

  This commit adds support for filenames prefixed	with "target:" to
exec_file_attach.  This is required to correctly follow inferior
exec* calls when a gdb_sysroot prefixed with "target:" is set.

gdb/ChangeLog:

	* exec.c (exec_file_attach): Support "target:" filenames.
---
 gdb/ChangeLog |    4 +++
 gdb/exec.c    |   71 +++++++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 56 insertions(+), 19 deletions(-)
  

On 03/20/2015 04:48 PM, Gary Benson wrote:
> This commit adds support for filenames prefixed	with "target:" to
> exec_file_attach.  This is required to correctly follow inferior
> exec* calls when a gdb_sysroot prefixed with "target:" is set.

Hmm, I don't see how.  Isn't this only true when target_pid_to_exec_file
prepends the sysroot, which it doesn't yet?  I think this should move
to that other series.

A couple bits could use more explanation (in commit log and/or
comments):

 - Why is writing into executable files not supported with "target:" ?
 - The skipping of gdb_realpath_keepfile.

Thanks,
Pedro Alves

> 
> gdb/ChangeLog:
> 
> 	* exec.c (exec_file_attach): Support "target:" filenames.
> ---
>  gdb/ChangeLog |    4 +++
>  gdb/exec.c    |   71 +++++++++++++++++++++++++++++++++++++++++---------------
>  2 files changed, 56 insertions(+), 19 deletions(-)
> 
> diff --git a/gdb/exec.c b/gdb/exec.c
> index 124074f..113e869 100644
> --- a/gdb/exec.c
> +++ b/gdb/exec.c
> @@ -176,36 +176,66 @@ exec_file_attach (const char *filename, int from_tty)
>      }
>    else
>      {
> +      int load_via_target = 0;
>        char *scratch_pathname, *canonical_pathname;
>        int scratch_chan;
>        struct target_section *sections = NULL, *sections_end = NULL;
>        char **matching;
>  
> -      scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST, filename,
> -		   write_files ? O_RDWR | O_BINARY : O_RDONLY | O_BINARY,
> -			    &scratch_pathname);
> -#if defined(__GO32__) || defined(_WIN32) || defined(__CYGWIN__)
> -      if (scratch_chan < 0)
> +      if (is_target_filename (filename))
> +	{
> +	  if (target_filesystem_is_local)
> +	    filename += strlen (TARGET_SYSROOT_PREFIX);
> +	  else
> +	    load_via_target = 1;
> +	}
> +
> +      if (load_via_target)
>  	{
> -	  char *exename = alloca (strlen (filename) + 5);
> +	  if (write_files)
> +	    warning (_("writing into executable files is "
> +		       "not supported for %s sysroots"),
> +		     TARGET_SYSROOT_PREFIX);
> +
> +	  scratch_pathname = xstrdup (filename);
> +	  make_cleanup (xfree, scratch_pathname);
>  
> -	  strcat (strcpy (exename, filename), ".exe");
> -	  scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST, exename,
> -	     write_files ? O_RDWR | O_BINARY : O_RDONLY | O_BINARY,
> -	     &scratch_pathname);
> +	  scratch_chan = -1;
> +
> +	  canonical_pathname = scratch_pathname;
>  	}
> +      else
> +	{
> +
> +	  scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST,
> +				filename, write_files ?
> +				O_RDWR | O_BINARY : O_RDONLY | O_BINARY,
> +				&scratch_pathname);
> +#if defined(__GO32__) || defined(_WIN32) || defined(__CYGWIN__)
> +	  if (scratch_chan < 0)
> +	    {
> +	      char *exename = alloca (strlen (filename) + 5);
> +
> +	      strcat (strcpy (exename, filename), ".exe");
> +	      scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST,
> +				    exename, write_files ?
> +				    O_RDWR | O_BINARY
> +				    : O_RDONLY | O_BINARY,
> +				    &scratch_pathname);
> +	    }
>  #endif
> -      if (scratch_chan < 0)
> -	perror_with_name (filename);
> +	  if (scratch_chan < 0)
> +	    perror_with_name (filename);
>  
> -      make_cleanup (xfree, scratch_pathname);
> +	  make_cleanup (xfree, scratch_pathname);
>  
> -      /* gdb_bfd_open (and its variants) prefers canonicalized pathname for
> -	 better BFD caching.  */
> -      canonical_pathname = gdb_realpath (scratch_pathname);
> -      make_cleanup (xfree, canonical_pathname);
> +	  /* gdb_bfd_open (and its variants) prefers canonicalized
> +	     pathname for better BFD caching.  */
> +	  canonical_pathname = gdb_realpath (scratch_pathname);
> +	  make_cleanup (xfree, canonical_pathname);
> +	}
>  
> -      if (write_files)
> +      if (write_files && !load_via_target)
>  	exec_bfd = gdb_bfd_fopen (canonical_pathname, gnutarget,
>  				  FOPEN_RUB, scratch_chan);
>        else
> @@ -218,7 +248,10 @@ exec_file_attach (const char *filename, int from_tty)
>  	}
>  
>        gdb_assert (exec_filename == NULL);
> -      exec_filename = gdb_realpath_keepfile (scratch_pathname);
> +      if (load_via_target)
> +	exec_filename = xstrdup (bfd_get_filename (exec_bfd));
> +      else
> +	exec_filename = gdb_realpath_keepfile (scratch_pathname);
>  
>        if (!bfd_check_format_matches (exec_bfd, bfd_object, &matching))
>  	{
>