Re: Re: Help: How to determine big/little endian?

> The fetch of an int from the union after storing a char is strictly illegal.


As a developer of a very aggressive optimizer for C/C++, I wish it
were illegal. Unfortunately, the C standard (and C++ draft standard)
say otherwise. See the end of Section 3.3 of the ANSI C standard and
the end of Section 5.0 of the ANSI working paper for C++. Both are
explicit that *any* object can be accessed as a character type.


It is perhaps unfortunate that C does not distinguish between bytes
for bit-twiddling and bytes for characters, but that's the way the
C/C++ languages have evolved.


Hence the code


> union { char c; int i; } u;
> u.i = 0; u.c = 1;
> swap = (u.i == 1) != IR->little_endian;


does not require that u be qualified as volatile in order to work correctly.


Arch D. Robison Kuck & Associates Inc.
robison@kai.com 1906 Fox Drive
217-356-2288 Champaign IL 61820


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