[RTEMS Project] #2967: ARM: Change ABI to not use short enums

[RTEMS trac]

#2967: ARM: Change ABI to not use short enums
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 Reporter:  Sebastian Huber  |      Owner:  joel.sherrill@…
     Type:  enhancement      |     Status:  new
 Priority:  normal           |  Milestone:  4.12.0
Component:  GCC              |    Version:
 Severity:  normal           |   Keywords:
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 Whether enums are short or not is left open in the ARM EABI. On Linux and
 FreeBSD no short enums are used.  Otherwise short enums are enabled by
 default.

 Short enums may cause hard to find issues with 3rd party software, since
 the are quite unusual in general, e.g.

 https://git.rtems.org/rtems-
 libbsd/commit/freebsd/include/rpc?id=9880635f2e642380b69b85e00271649b3a2fc2de

 The data and structure layout may suddenly change in case enumeration
 values are added/removed.  The benefit of short enums is probably not
 worth the trouble, since the packed compiler attribute can be used to
 individually make an enum short.

 The reason for not choosing no short enums during the ARM EABI
 introduction was an issue with Newlib.  This is addressed with the
 following patch:

 https://sourceware.org/ml/newlib/2017/msg00238.html

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Ticket URL: <http://devel.rtems.org/ticket/2967>
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