[MacPorts] #55577: getting rid of unforeseen -I${prefix}/include option adding and its potential side-effects

[MacPorts]

#55577: getting rid of unforeseen -I${prefix}/include option adding and its
potential side-effects
--------------------------+-----------------
  Reporter:  RJVB         |      Owner:
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  pcre, glib2  |
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Comment (by RJVB):

 I cannot really comment on the idea of using -isystem . It might work as
 you suggest, but it might depend on whether clang or gcc is used. IIRC
 they differ in the way they do this sort of thing for libraries, they
 could also for headers. I forget the details and have more urgent things
 to pursue right now :-/

 I don't claim this is specific to MacPorts. I do suppose that any
 comparable distribution system will run into similar issues sooner or
 later. One could check if any other such system has solutions in place
 (Gentoo Prefix would be a good candidate).
 MacPorts may in fact be a little less vulnerable because the real system
 header file locations are less likely to contain conflicting older
 versions.

 > This will not work if pkgconfig is not installed at the time the user
 requests to install git.

 I guess I should set it in the pre-build indeed? I'm so used to doing the
 configure and build steps separately that I tend to forget this. I did try
 to set this up with options variables and defaults, but that became very
 complicated with a number of unwanted curly braces in the CFLAGS string.

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Ticket URL: <https://trac.macports.org/ticket/55577#comment:8>
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