Re: [Xen-devel] [PATCH] tools/check: check for headers and libraries in EXTRA_INCLUDES and EXTRA_LIB

[Roger Pau Monné <roger.pau@xxxxxxxxxxxxx>]

2011/10/18 Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>:
> Roger Pau Monné writes ("Re: [Xen-devel] [PATCH] tools/check: check for 
> headers and libraries in EXTRA_INCLUDES and EXTRA_LIB"):
>> 2011/10/17 Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>:
>> > Perhaps this would be more easily achieved with "export" ?
>>
>> Exported variables are not passed to the called program (chk in this case).
>
> Are you sure ?  One purpose of "export" is to put the variable in the
> environment of commands make runs.

I'm not an expert on Makefiles, but from what I've found on the
internet, export is used to pass variables to sub-makefiles:
http://www.gnu.org/s/hello/manual/make/Variables_002fRecursion.html
but I couldn't find any reference about using export to pass variables
to executed commands. I've tried:

export PYTHON
export LIBXENAPI_BINDINGS
....
./chk build

And variables where not passed to executed script. At the end I think
the most suitable solution is to use:

PYTHON=$(PYTHON) \
LIBXENAPI_BINDINGS=$(LIBXENAPI_BINDINGS) \
....
./chk build

To avoid having long lines. This way works fine, variables are passed
to the called script.

>> > The check_sys_root stuff seems unrelated ?  Or at least, it's not
>> > mentioned in your commit message.  I'm not sure if it should be
>> > disentangled but it should definitely be mentioned.  (I'm not much of
>> > an expert on tools/check.)
>>
>> The check_sys_root call was already there, just moved it to the top,
>> but I don't know if it's really necessary.
>
> Why do you move it ?

Because if I found the requested headers in one of the folders while
doing the for loop I perform a return 0, I could also perform a break
and left the check_sys_root at the end, but does it really matter that
much to check_sys_root at the start or at the end of has_header?
Looking at the code of the function it doesn't seem to matter when it
is performed.

> Ian.
>

Thanks, Roger.

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