Re: [PATCH] Avoid harmful fall throughs in core_target::xfer_partial.

[Pedro Alves <pedro@palves.net>]

On 2022-03-16 19:36, John Baldwin wrote:
> The cases for TARGET_OBJECT_LIBRARIES and TARGET_OBJECT_LIBRARIES_AIX
> can try to fetch different data objects (such as
> TARGET_OBJECT_SIGNAL_INFO) if gdbarch methods for the requested data
> aren't present.  Replace case fallthroughs with an explicit goto to
> the default case.

This is OK.  I mean, I think it would be reasonable to instead return
TARGET_XFER_E_IO -- it's what the other cases do (notice even TARGET_OBJECT_SIGNAL_INFO
doesn't fallback to the beneath target if there's no gdbarch method installed), and the targets
beneath (file and dummy) won't be returning any library anyhow.  OTOH, maybe some day we will
teach GDB to read the list of libraries the program is linked with and load those before
the program starts, and it's conceivable that we would do that at the file_stratum layer.

Pedro Alves

> ---
>  gdb/corelow.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/corelow.c b/gdb/corelow.c
> index 1579e6bc2b8..f7f2bd3f318 100644
> --- a/gdb/corelow.c
> +++ b/gdb/corelow.c
> @@ -943,7 +943,7 @@ core_target::xfer_partial (enum target_object object, const char *annex,
>  		return TARGET_XFER_OK;
>  	    }
>  	}
> -      /* FALL THROUGH */
> +      goto fallthrough;
>  
>      case TARGET_OBJECT_LIBRARIES_AIX:
>        if (m_core_gdbarch != nullptr
> @@ -964,7 +964,7 @@ core_target::xfer_partial (enum target_object object, const char *annex,
>  		return TARGET_XFER_OK;
>  	    }
>  	}
> -      /* FALL THROUGH */
> +      goto fallthrough;
>  
>      case TARGET_OBJECT_SIGNAL_INFO:
>        if (readbuf)
> @@ -988,6 +988,7 @@ core_target::xfer_partial (enum target_object object, const char *annex,
>        return TARGET_XFER_E_IO;
>  
>      default:
> +    fallthrough:
>        return this->beneath ()->xfer_partial (object, annex, readbuf,
>  					     writebuf, offset, len,
>  					     xfered_len);