Re: [Boost-build] What variables available in actions (was Re: actions bind doc slightly confusion and what variables available in actions?

From: Vladimir Prus (ghost_at_[hidden])
Date: 2007-08-04 10:30:13

Larry Evans wrote:

> On 08/03/2007 01:23 PM, Larry Evans wrote:
> [snip]
>> * question 2
>> 
>> The following is from gcc.jam:
>> <-------- cut here ---------
>> actions link bind LIBRARIES
>> {
>>      "$(CONFIG_COMMAND)" -L"$(LINKPATH)"
>> -Wl,$(RPATH_OPTION:E=-R)$(SPACE)-Wl,"$(RPATH)"
>> -Wl,-rpath-link$(SPACE)-Wl,"$(RPATH_LINK)" -o "$(<)" $(START-GROUP)
>> "$(>)" "$(LIBRARIES)" -l$(FINDLIBS-ST) -l$(FINDLIBS-SA) $(END-GROUP)
>> $(OPTIONS) $(USER_OPTIONS)
>> #the above appears all on one line in my editor.
>> }
>> 
>>  >-------- cut here ---------
>> 
>> What variable values are available in the actions body?  Was the
>> 'bind LIBRARIES' needed because it wasn't among the set of
>> variables passed to all actions or just actions for link commands
>> or is there some other criteria for determining the variables
>> passed to the actions body?
> 
> Part of the answer to this is, maybe, provided by:
> 
> http://www.boost.org/doc/html/bbv2/extender.html#bbv2.extending.features
> 
> which contains:
> 
> Then, the flags invocation says that whenever verbatin.inline-file
> action is run, the value of the verbatim-options feature will be added
> to the OPTIONS variable, and can be used inside the action body.
> 
> So, are RPATH_LINK, FINDLIBS-ST, FINDLIBS-SA, OPTIONS, and USER_OPTIONS
> all declared as features of the gcc toolset (or more precisely,
> the superclass of gcc, i.e. the unix toolset)?

A rule can use the following variables:

1. Variables globally set in the module an action is in.
2. A variable set "on target"

On Boost.Build, the "on target" variables to set are described via
the 'flags' rule. So, this line from gcc.jam:

        flags $(toolset).link RPATH_LINK $(condition) : <xdll-path> : unchecked ;

makes RPATH_LINK available in the 'link' action.

The 'bind' you was asking is somewhat different -- when a variable used in action
is a string, it can be just used. But when a variable is a name of jam's low-level
target, one has to use 'bind' to get the pathname inside the action, not the target's
name.

Finally, I don't really remember if modifiers should be used before action name
or after -- using 'bind' after apparently works.

- Volodya

> 
> 
> _______________________________________________
> Unsubscribe & other changes:
> http://lists.boost.org/mailman/listinfo.cgi/boost-build