Cannot override positional-dependent options

[toonetown]

With the change at https://github.com/boostorg/build/commit/61989801cab6a8f92969fcb82340a1e299e14e5e a (perhaps) unintended side effect is that options specified in a project-config.jam file are no longer listed last - so those options (-fvisibility for example) which are position-dependent (later ones override earlier ones), there is no longer a way to override.

This can be seen by looking at the compile commands for boost::log and boost::serialization if you specify <cxxflags>-fvisibility=default in project-config.jam. Prior to this commit (and, rolling back this commit) will place the -fvisibility=default after -fvisibility=hidden. After this commit, the -fvisibility=hidden comes after, thus not providing a way to override the option.

I am attaching a project-config.txt file. Building boost::log with clang on macOS will demonstrate the issue.

[swatanabe]

AMDG

In general, controlling option order is poorly supported by Boost.Build. This particular issue has always been handled inconsistently between toolsets. This changeset makes the behavior the same as for gcc. In addition, the generic behavior for Boost.Build is that local options override global ones, so having the toolset options override the requirements on specific targets is somewhat problematic to begin with.

In Christ, Steven Watanabe

[toonetown]

I am OK with the way it is - especially if it means more consistency. I would value consistency over configurability. The reason I logged this was that it was a change in behavior from one version to another (and it was a change that happened to bite me).

If there were a way to specify something to go in to the $(USER_OPTIONS) variable, that would completely solve my problem. How do you get values into there? When I specify values, such as <cxxflags>, in project-config.jam they appear to go into the $(OPTIONS).

Perhaps this is a documentation task instead of a change in functionality.

[swatanabe]

AMDG

On 08/09/2018 08:17 PM, Nathan Toone wrote:

I am OK with the way it is - especially if it means more consistency. I would value consistency over configurability. The reason I logged this was that it was a change in behavior from one version to another (and it was a change that happened to bite me).

If there were a way to specify something to go in to the $(USER_OPTIONS) variable, that would completely solve my problem. How do you get values into there? When I specify values, such as <cxxflags>, in project-config.jam they appear to go into the $(OPTIONS).

If you put this in project-config.jam, it will end up in USER_OPTIONS:

project : requirements clang-darwin:-fvisibility=default ;

However, this won't actually solve your problem, because -fvisibility=hidden is also in USER_OPTIONS and the options are sorted alphabetically, in this case. There is a syntax to control option order explicitly, but IIRC, it only works for path features.

In Christ, Steven Watanabe

[stale[bot]]

Thank you for your contributions. Main development of B2 has moved to https://github.com/bfgroup/b2 This issue has been automatically marked as "transition" to indicate the potential for needing transition to the new B2 development project.