[MacPorts] #40656: Use -isystem instead of -I in default configure.cppflags

[MacPorts]

#40656: Use -isystem instead of -I in default configure.cppflags
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  Reporter:  ryandesign   |      Owner:  macports-tickets@…
      Type:  enhancement  |     Status:  reopened
  Priority:  Normal       |  Milestone:  MacPorts Future
 Component:  base         |    Version:  2.2.0
Resolution:               |   Keywords:  haspatch
      Port:               |
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Comment (by DanEble):

 Greetings.  I'm speaking as a developer of GNU LilyPond investigating our
 [https://gitlab.com/lilypond/lilypond/-/issues/6135 issue 6135], which is
 an error while compiling the MacPorts port.

 From reading the build log provided to me, I believe that the main issue
 is that MacPorts sets up the build to search /opt/local/include with -I
 rather than -isystem.  (Note that I am not currently a MacPorts user and I
 have not tried to reproduce the issue myself.)

 Using -I makes headers in that directory subject to the same compiler
 warnings as project-specific headers, which is undesirable in my view.
 There are warnings (one of which is currently treated as an error) that we
 benefit from enabling for LilyPond headers, but which we do not want to to
 enable for external headers.  In our own build scripts, we distinguish
 external headers with -isystem.

 I would like to find out whether MacPorts developers are willing to
 address this issue in MacPorts the near future.  Seeing that the previous
 comment is seven years old, I guess that this issue has either been
 forgotten or that there is no real interest in ever doing it.  Which one
 is it?

 Thanks and regards.

-- 
Ticket URL: <https://trac.macports.org/ticket/40656#comment:20>
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