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Re: [LLVMdev] FYI: IA-32 psABI draft version 0.1
- From: Richard Smith <richard at metafoo dot co dot uk>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GCC Development <gcc at gcc dot gnu dot org>, GNU C Library <libc-alpha at sourceware dot org>, Binutils <binutils at sourceware dot org>, "cfe-dev at cs dot uiuc dot edu Developers" <cfe-dev at cs dot uiuc dot edu>, "llvmdev at cs dot uiuc dot edu Mailing List" <llvmdev at cs dot uiuc dot edu>
- Date: Thu, 22 Jan 2015 11:54:51 -0800
- Subject: Re: [LLVMdev] FYI: IA-32 psABI draft version 0.1
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOppN+Rfb-8FPrXN4BxsrMEeh0ChmN+aWmGKyi6iRu=3aQ at mail dot gmail dot com>
On Thu, Jan 22, 2015 at 4:35 AM, H.J. Lu <email@example.com> wrote:
> Here is the link:
The document contains this claim (as do many other psABI documents):
"Bit-fields that are neither signed nor unsigned
always have non-negative values. Although they may have type char,
short, int, or long (which can have negative values), these bit-fields
have the same range as a bit-field of the same size with the
corresponding unsigned type."
This does not reflect the ABI as widely implemented, and is
incompatible with C++ (in which plain bit-fields are required to be
GCC documents why they ignore the psABI in this regard here:
I would suggest either removing this specification from the psABI or
correcting it to reflect actual implementation practice: plain
bit-fields are signed.