[MacPorts] #52699: cmake portgroup version 1.1

[MacPorts]

#52699: cmake portgroup version 1.1
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  Reporter:  mkae         |      Owner:  mkae
      Type:  enhancement  |     Status:  accepted
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  cmake        |
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Comment (by RJVB):

 >This parsing code is very fragile. There’s almost certainly a better
 approach. Can you explain again why it is necessary at all? I am not very
 familiar with CMake.

 I've been using this code for months now, and never had issues with it.
 You're probably right it's fragile but in practice it seems to work well
 enough, and it shouldn't drop any options which is probably the most
 important part.

 You have much of the explanation right in the text you quoted. CMake
 defines 4 build types that each come with their own set of compiler
 options. Options set in the environment (CFLAGS, CXXFLAGS, etc) are not
 ignored, but they are prepended to the options CMake imposes. So if a port
 or user wants to build with -O3 but the build type wants -O2, you get `-O3
 -O2` which equals -O2. It's tricky to override this, unless you specify  a
 custom build type which evidently doesn't come with predefined compiler
 options. Then you get only the options you set in the environment.

 The brunt of the parsing however concerns configure.cppflags. This is done
 because CMake doesn't have an equivalent, it only has an option to define
 the include path (which has to be done in one go, not in incremental
 steps). So to be sure that all specified  include paths are known to CMake
 this parser rewrites configure.cppflags so that it contains only the
 -I/foo and `-I /foo` options. All other options are moved to
 configure.*cflags and configure.*cxxflags.

 > Note that base augments several options before setting up the
 environment variables.

 Meaning I should output `$::env(CXXFLAGS)`, or does it not yet have its
 final value in the pre-configure?
 Not that this is crucial, but it'd be nice to get it right.

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Ticket URL: <https://trac.macports.org/ticket/52699#comment:20>
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