Re: [boost] Proposal for moving Boost to CMake

Subject: Re: [boost] Proposal for moving Boost to CMake
From: Edward Diener (eldiener_at_[hidden])
Date: 2017-06-19 22:12:38

On 6/19/2017 2:28 PM, Daniel James via Boost wrote:
> On 19 June 2017 at 01:53, Gary Furnish via Boost <boost_at_[hidden]> wrote:
>> For whatever its worth as a user who sometimes contributes patches to
>> fix bugs, I don't use the system compiler and instead use scripts to
>> test different builds of internal code (clang, clang with various
>> sanitizers and options, different versions of gcc, etc).  This is such
>> a pain with boost build because of the difficulty of automating
>> building multiple copies with custom compilers and flags with the same
>> source tree.  In cmake this is easy, you just change some command line
>> flags, something trivial in scripts.  In Boost, I think I got it
>> working once using undocumented features after spending several hours
>> looking around at docs, source code(!), and stack overflow.  I now
>> automatically just don't use boost
>> libraries that aren't header only.  I would rather rewrite code than
>> fight with the build process. That is a bad state of affairs.
> 
> That's odd, that's one thing I've always found easier with boost build
> than any other build system. You add a target to your user-config.jam,
> such as:
> 
> using gcc : sanitize : g++ -fsanitize=address ;
> 
> Then run the build using something like 'b2 gcc-sanitize'.

I have been doing something similar. But according to the Boost Build 
docs ( 
http://www.boost.org/build/doc/html/bbv2/reference/tools.html#bbv2.reference.tools.compiler.gcc 
) the "sanitize" in your example is the gcc version. So I might have the 
equivalent of:

using gcc : 6.3sanitize : g++ : -fsanitize=address ;

and I no doubt delude myself in thinking that when I might run 'b2 
gcc-6.3sanitize' that Boost Build actually checks that the version I am 
using is gcc 6.3. In the docs it does not really say what Boost Build 
actyally does with that 'version' in the using gcc rule.

> I think
> there's some way of specifying flags at the command line

'b2 gcc-sanitize cxxflags=-fsanitize=address'

should also work.

>, but I find
> it's easier just to set up a number of configurations in the
> configuration file. So when developing unordered, if I want to run the
> insert tests, I might do something like this:
> 
> cd libs/unordered/test
> b2 -q insert_tests gcc gcc-std11 clang clang-std14

I agree with you but I am pretty sure the problem is end-users trying to 
understand that you can do these things with Boost Build. It is not so 
much that the information is not in the Boost Build docs as it is that 
the docs themselves are not geared nearly well enough for the beginning 
end-user of Boost Build to make it easy for them to understand what you 
can do with it.

> 
> I have no idea how to do the same thing with cmake. As far as I'm
> aware with cmake you have to set up multiple build directories for
> each variant of each project. I've found it a real pain for building
> projects like libc++.
> 
> Just to make it clear, I'm far from an expert in boost build, and
> struggle with many other aspects. But I've never found cmake to be the
> land of milk and honey that I hear so much about. I'm also more than a
> bit fed up of cleaning up after other people's grand projects.