Determining cancellation points in glibc

Loic Domaigne
Tue Nov 25 20:47:00 GMT 2008

Hi Carlos,

> On Mon, Nov 24, 2008 at 3:49 PM, Loic Domaigne <> wrote:
>> I came to similar conclusions. But what about composite functions like
>> printf(), scanf() etc.?
> Good point.
> 5. Any C code contains a cancellation point if it calls functions from
> 1-4 which contains a cancellation point.

I was afraid of that...

As you may know, POSIX defines two list: mandatory and optional 
cancellation points (CP). The problem that we have: we need to document 
if a particular functions in the "optional list" is CP or not. This will 
be a hell of work to figure this out.

The next issue I see: POSIX states that the no other functions except 
the ones listed in the mandatory and optional list may be CP. So a 
natural question arise: how does the Glibc folks enforce this? Through 
code review? Other means, like compiler flags etc. ?

Thanks & Regards,

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