setrlimit always fails

[Brian Inglis]

On 2021-02-11 19:06, Ken Brown via Cygwin wrote:
> On 2/11/2021 10:23 AM, Patrick Chkoreff wrote:
>> I'm trying to use setrlimit to impose limits on various resources such
>> as CPU time and memory.  The call to setrlimit always fails.  I've
>> distilled this into the following example test.c:
> [...]
>>      if (setrlimit(RLIMIT_CPU,&rlim) < 0)
> [...]
>> setrlimit: Invalid argument
> 
> Cygwin's setrlimit only supports a few resources, as you can see in the source:
> 
> https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/resource.cc;h=97777e9d223466b7635b990d6c9e0bfb9e2e9a46;hb=HEAD#l201 

In that case could I suggest:

	/usr/share/doc/cygwin-doc/html/cygwin-api/compatibility.html#std-susv4
	https://cygwin.com/cygwin-api/compatibility.html#std-susv4

in https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/doc/posix.xml

get/setrlimit entries should be annotated with:

	(see chapter "Implementation Notes")

and all those entries should be links to "std-notes":

	/usr/share/doc/cygwin-doc/html/cygwin-api/std-notes.html
	https://cygwin.com/cygwin-api/std-notes.html

	<ulink url="std-notes.html">(see chapter "Implementation Notes")</ulink>

in https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/doc/posix.xml

which should have an entry documenting the limitations of get/setrlimit like e.g.

"<para><function>getrlimit</function> resources RLIMIT_AS, RLIMIT_CPU, 
RLIMIT_FSIZE, RLIMIT_DATA always return rlim_cur and rlim_max as RLIM_INFINITY, 
so <function>setrlimit</function> returns -1 and sets EINVAL if they are 
lowered, or returns 0 if unchanged.
<function>getrlimit</function> resource RLIMIT_NOFILE always returns rlim_cur 
and rlim_max as OPEN_MAX; <function>setrlimit</function> returns 0 sets EINVAL 
if rlim_cur > rlim_max, does not change the value if it is RLIM_INFINITY, 
otherwise returns the result from <function>setdtablesize</function>.
<function>getrlimit</function>/<function>setrlimit</function> resources 
RLIMIT_CORE and RLIMIT_STACK return the current values and set the requested values.
All other resource arguments return -1 and set EINVAL.</para>"

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

This email may be disturbing to some readers as it contains
too much technical detail. Reader discretion is advised.
[Data in binary units and prefixes, physical quantities in SI.]