Re: [jamboost] Re: Re: Re: Re: [boost] Comeau setup

From: Rene Rivera (grafik666_at_[hidden])
Date: 2002-07-10 15:17:23

[2002-07-10] gclbb-jamboost_at_[hidden] wrote:

>In article <019401c225e0$bebcee30$6601a8c0_at_[hidden]>,
>David Abrahams <jamboost_at_[hidden]> wrote:
>>Comeau wrote:
>>As for how they interact, if you set COMO_PATH, you will
>>automatically get defaults for the others. If they point to
>>the right places as described by the "Semantics" column, you're done.
>
>This is one root of my question, because I don't see how.
>For instance, how does COMO_PATH set COMO_BIN_PATH and
>COMO_ROOT_DIRECTORY? And so on.

[from como-tools.jam...]

[sets COMO_BASE if not already set by the user]
COMO_BASE ?= $(COMO_PATH) ;

[sets COMO_BIN_DIRECTORY to either COMO_BIN_PATH, COMO_BASE/bin/, or "",
that is more precisely to the first that has a value]
COMO_BIN_DIRECTORY ?= $(COMO_BIN_PATH) ;
COMO_BIN_DIRECTORY ?= $(COMO_BASE)$(SLASH)bin$(SLASH) ;
COMO_BIN_DIRECTORY ?= "" ;

[etc... :-]

But that doesn't actually answer your question because the Jam code
currently(1.28.0) doesn't set "COMO_BIN_PATH", it only uses it and therefore
can only be set by the user. And "COMO_ROOT_DIRECTORY" is not used at all.
For that not setting COMO_PATH makes things not have values or have "" as
the value, causing the default como behaviour to occur, and requires that it
be in the PATH.

Maybe the detail your aren't aware of yet is that in Jam a variable can have
no-value. And when it doesn't have a value it's expansion dooesn't generate
a value either. For example:

SOME_VAR = ; # no-value
ANOTHER_VAR = $(SOME_VAR)/some/stuff ; # still no-value

>>The system will only resort to using PATH for the como toolset
>>if you don't specify COMO_PATH.
>
>Does it do that explicitly, or only as a fallout of the jam file(??)
>being unable to do so?

As a fallout, see above.

>>(e.g. como uses "LIB",
>
>Actually, that's another question I had, because it looks as if
>you're adding libcomo into LIB, and probably that's not the
>best setup (actually, I seem to recall that doesn't work all the time).

Why is it not best? And when doesn't it not work? As it looks to me it
actually does that on Windows, but in addition also adds it to the command
line explicitly.

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