[MacPorts] #57539: legacysupport-1.0: Let ports specify what symbols they need

[MacPorts]

#57539: legacysupport-1.0: Let ports specify what symbols they need
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  Reporter:  ryandesign     |      Owner:  (none)
      Type:  defect         |     Status:  new
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:
Resolution:                 |   Keywords:
      Port:  legacysupport  |
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Comment (by kencu):

 in the build sources for the library, the symbols are disabled on systems
 that have them already.

 For example, the strnlen.c source will be actually built only on 10.6 and
 earlier. On 10.7 and later, it is bypassed by a guard, and there is not
 code built.

 Similar for all the other replaced functions.

 It took me a while to notice this.

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Ticket URL: <https://trac.macports.org/ticket/57539#comment:1>
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