[PATCH] Add support for -funsigned-bitfields
Artyom.Skrobov at arm.com
Thu Jan 30 06:27:27 PST 2014
>> Compatibility with GCC is a means to an end -- we
>> primarily aim to be compatible with GCC in order
>> to make it easy for people to move code between
>> GCC and Clang. Is there some particular code
>> that relies on this? Is there a good reason to
>> think it's better to implement this feature in
>> Clang rather than fixing the code that relies on
> IIUC, this is in GCC because it was an old RVCT
> feature, and it was so probably because an
> ancient user needed for some obscure reason that
> was only valid on a very narrow embedded context.
> Maybe ARM folks can explain the rationale behind
> this on any modern codebase.
Yes, that's indeed a legacy feature of ARM Compiler to default to the "more
efficient" data type, one that doesn't require a sign extension on a fetch.
We have to admit that supporting this feature is more trouble than it's
worth, and it would indeed be preferable to fix the legacy code to use
Thanks for sharing the insight about the non-obvious implications of this
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