Re: [RFC] Add possibility to force buffering mode for stdout/stderr

[Yao Qi <yao@codesourcery.com>]

On 08/21/2013 11:08 PM, Pierre Muller wrote:
> basically adding
> "-ex {maint setvbuf stdout full 1000000}"
> or
> "-ex {maint setvbuf stdout line 80}"
> should allow to test both performance differences
> induced by buffering changes and possible regressions
> in testsuite results.
>
> This patch is really only of interest to developers
> using the testsuite or wanting to investigate
> performance issues related to buffering.

Pierre,
I am afraid we can't call setvbuf on-the-fly to adjust the buffering to
a stream.

   "The setvbuf() function may be used after the stream pointed to by
stream is associated with an open file but before any other operation"
See http://pubs.opengroup.org/onlinepubs/009696699/functions/setvbuf.html

setvbuf on Windows has similar requirement.

Even this command is only used once like "-ex {maint setvbuf stdout full 
1000000}" or "-iex {maint setvbuf stdout line 80}", they are executed 
after GDB printed version info to stdout, so it is not right to call 
setvbuf, IMO.

-- 
Yao (齐尧)