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Subject: Re: [Boost-build] ordering of compiler flags
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2017-07-21 15:38:24


On 07/21/2017 09:30 AM, Stefan Seefeld via Boost-build wrote:
> working on my Python frontend for Boost.Build, I'm reminded of a
> long-standing question I have been having about features / properties.
> In certain cases, compilers are very sensitive to the ordering of
> specific options (search paths, for example, or linker flags). While I
> can define my own order when defining a property locally, I wonder how
> the ordering of properties is managed across multiple locations, i.e.
> when properties are combined (from multiple requirements, for example).
> Is the data flow for property definitions formally specified anywhere ?

They're sorted alphabetically.

> Other build tools (e.g. SCons) have functions to explicitly prepend or
> append, as well as indicate that a flag is only to be prepended /
> appended if not yet present. Is there a way to achieve the same with b2
> ? (For avoidance of doubt: I'm not asking about doing that locally, i.e.
> where I can manipulate a single property set. The question is about
> doing that globally, in the context of multiple property sets being
> eventually merged. (It seems and attribute like "unique" could be a
> property of a feature itself, but I didn't see it there. Likewise, I do
> see "order-sensitive", but am not sure how it is being used.

order-sensitive is not implemented.

In Christ,
Steven Watanabe

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