Re: controlling stdio buffering

[Pádraig Brady]

Andreas Schwab wrote:

>Pádraig Brady <address@hidden> writes:
>
>  
>
>>It's just that above call seems to have no affect,
>>    
>>
>
>The standard does not require that setvbuf has any visible effect apart
>from honoring the buffering mode.
>
>    7.19.5.6 The setvbuf function
>
>    ... If buf is not a null pointer, the array it points to may be used
>    instead of a buffer allocated by the setvbuf function and the argument
>    size specifies the size of the array; otherwise, size may determine
>    the size of a buffer allocated by the setvbuf function. ...
>
>Note the use of "may" instead of "shall".
>  
>
Yes the "size may determine the size of a buffer allocated by the
setvbuf function".
But glibc does not do this and hence should report non 0 to say it's not
honoured.
If the platform does support internal buffer allocation, then that could
fail also
resulting in a non 0 return. In either case the application will want to
know if
it got the requested buffer size or not.

I'm also confused about the default buffer sizes.
On my libc6-2.3.5-1ubuntu1 stdin buffer defaults to 4096, stdout to 1024
and BUFSIZ is 8192 ?

cheers,
Pádraig.