From owner-svn-src-all@freebsd.org  Tue Jan 17 19:37:35 2017
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Subject: Re: svn commit: r312296 - in head: lib/libc/sys sys/kern sys/netinet
 sys/netinet6 sys/sys tools/regression/sockets/udp_pingpong
 tools/regression/sockets/unix_cmsg
To: Benjamin Kaduk <bjkfbsd@gmail.com>, Ian Lepore <ian@freebsd.org>
References: <201701161746.v0GHkcPX071529@repo.freebsd.org>
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Cc: Maxim Sobolev <sobomax@freebsd.org>, Gleb Smirnoff <glebius@freebsd.org>, 
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From: Eric van Gyzen <vangyzen@FreeBSD.org>
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Date: Tue, 17 Jan 2017 13:37:27 -0600
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On 01/17/2017 11:48, Benjamin Kaduk wrote:
> On Tue, Jan 17, 2017 at 10:57 AM, Ian Lepore <ian@freebsd.org
> <mailto:ian@freebsd.org>> wrote:
> 
>     In my experience, enums are a superior way to define integer constants
>     (compared to #define), but they are pure poison as variable types in
>     APIs and structures because their size is a compiler implementation
>     choice.
> 
> 
> Well, to some extent. For example, the amd64 sysV ABI says that enum
> types are signed fourbyte, with a footnote that "C++ and some
> implementations of C permit enums larger than an int. The underlying
> type is bumped to an unsigned int, long int or unsigned long int, in
> that order."

And in C++11 and later, you can specify the exact type:

enum color
#if defined(__cplusplus) && __cplusplus >= 201103L
	: int
#endif
{
	blue,
	...

Eric