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| Union C++ standard DrDiettrich1@netscape.net (Hans-Peter Diettrich) (2021-11-25) |
| Re: Union C++ standard 480-992-1380@kylheku.com (Kaz Kylheku) (2021-11-26) |
| Re: Union C++ standard gah4@u.washington.edu (gah4) (2021-11-26) |
| Re: Union C++ standard david.brown@hesbynett.no (David Brown) (2021-11-27) |
| Re: Union C++ standard derek@NOSPAM-knosof.co.uk (Derek Jones) (2021-11-28) |
| Re: Union C++ standard david.brown@hesbynett.no (David Brown) (2021-11-28) |
| Re: Union C++ standard derek@NOSPAM-knosof.co.uk (Derek Jones) (2021-11-29) |
| [7 later articles] |
| From: | Hans-Peter Diettrich <DrDiettrich1@netscape.net> |
| Newsgroups: | comp.compilers |
| Date: | Thu, 25 Nov 2021 11:11:04 +0100 |
| Organization: | Compilers Central |
| Injection-Info: | gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="44177"; mail-complaints-to="abuse@iecc.com" |
| Keywords: | C, standards |
| Posted-Date: | 26 Nov 2021 12:31:56 EST |
Can somebody explain why the access to members of a union is "undefined"
except for the most recently written member?
What can be undefined in a union of data types of the same typesize end
alignment? Any member written will result in a unique bit/byte pattern
in memory, whose reading may not make sense in a different type but
undoubtedly is well defined.
DoDi
[I think it's undefined in a standards sense. In any individual
implementation the result is predictable, but it's not portable. -John]
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