[MacPorts] #69681: gsl @2.7.1: error: implicitly declaring library function 'exit'

[MacPorts]

#69681: gsl @2.7.1: error: implicitly declaring library function 'exit'
-------------------------+--------------------------
  Reporter:  ryandesign  |      Owner:  daitakahashi
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.9.3
Resolution:              |   Keywords:  haspatch
      Port:  gsl         |
-------------------------+--------------------------

Comment (by Dave-Allured):

 Oh sorry, I forgot about the second part above, whitelist `strchr`.  That
 is still needed in the portfile.

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Ticket URL: <https://trac.macports.org/ticket/69681#comment:3>
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