Re: [PATCH] Do partial xfers from trace file

[Stan Shebs <stan at codesourcery dot com>]

Mike Frysinger wrote:
> On Monday 05 April 2010 18:10:49 Stan Shebs wrote:
>   
> > Memory blocks in the trace buffer are limited to 65K (to save a couple
> > bytes in the length field, since most blocks are small), and a tester
> > trying to collect a quarter-megabyte(!) C++ object ran into trouble with
> > that.  The fix is really a target-side thing, but the trace file reader
> > needs to cognizant of this detail also.  Fortunately, we can exploit
> > GDB's partial xfer mechanism, and just return what we find in one block,
> > expecting that GDB will re-request the remainder.
> >
> > I also made the tfile target has_all_memory, and added an emulation of
> > QTro behavior, which lets disassembly and the like work, but rejects
> > attempts to print non-constant globals that were not collected.
> > Committed to trunk.
> >     
>
> there's some problems with this commit ...
>
> it introduces a warning which breaks with -Werror:
> tracepoint.c: In function âtfile_xfer_partialâ:
> tracepoint.c:3895: error: ignoring return value of âreadâ, declared with 
> attribute warn_unused_result
>   

It's a little weird that some people get a complaint and others 
don't...  In any case, it's just an oversight, all the other read 
results are being checked, and so I just committed the fix below.

Stan

2010-04-12  Stan Shebs  <stan@codesourcery.com>

   * tracepoint.c (tfile_xfer_partial): Check read result.

Index: tracepoint.c
===================================================================
RCS file: /cvs/src/src/gdb/tracepoint.c,v
retrieving revision 1.177
diff -p -r1.177 tracepoint.c
*** tracepoint.c    9 Apr 2010 20:46:40 -0000    1.177
--- tracepoint.c    13 Apr 2010 03:52:28 -0000
*************** tfile_xfer_partial (struct target_ops *o
*** 3892,3898 ****
           if (amt > len)
         amt = len;

!           read (trace_fd, readbuf, amt);
           return amt;
           }
       lseek (trace_fd, mlen, SEEK_CUR);
--- 3892,3905 ----
           if (amt > len)
         amt = len;

!           gotten = read (trace_fd, readbuf, amt);
!           if (gotten < 0)
!         perror_with_name (trace_filename);
!           /* While it's acceptable to return less than was
!          originally asked for, it's not acceptable to return
!          less than what this block claims to contain.  */
!           else if (gotten < amt)
!         error (_("Premature end of file while reading trace file"));
           return amt;
           }
       lseek (trace_fd, mlen, SEEK_CUR);