From: Olivier MARTIN <olivier@labapart.com>
To: Clemens Ladisch <clemens@ladisch.de>
Cc: Marcus Shawcroft <marcus.shawcroft@gmail.com>,
Newlib Mailing List <newlib@sourceware.org>,
olivier@labapart.com
Subject: Re: Building newlib for Cortex-M with LLVM
Date: Thu, 12 Nov 2015 13:46:00 -0000 [thread overview]
Message-ID: <758ffcb7b7a715815f410b3b6bd1316e@labapart.com> (raw)
In-Reply-To: <5644870C.6040106@ladisch.de>
On 12.11.2015 12:33, Clemens Ladisch wrote:
> Marcus Shawcroft wrote:
>> On 11 November 2015 at 23:16, Olivier MARTIN <olivier@labapart.com>
>> wrote:
>>> * The first one can be solved. The space in the call of CONCAT2(a, b)
>>> by
>>> CONCAT() is propagated into the subsequent calls. It means when the
>>> strings
>>> 'a' and 'b' are concatenated, the space is inserted between both
>>> strings -
>>> which is not the expected behaviour.
>>>
>>> The fix would be:
>>>
>>> -#define CONCAT(a, b) CONCAT2(a, b)
>>> +#define CONCAT(a, b) CONCAT2(a,b)
>>
>> Have you looked at the C standard on this issue? I wonder which
>> compiler, gcc or clang is not compliant with the standard.
>
> 6.10.3.3:
> | If, in the replacement list of a function-like macro, a parameter is
> | immediately preceded or followed by a ## preprocessing token, the
> | parameter is replaced by the corresponding argumentâs preprocessing
> | token sequence; [â¦]
> | each instance of a ## preprocessing token in the replacement list
> | (not from an argument) is deleted and the preceding preprocessing
> | token is concatenated with the following preprocessing token.
>
> Preprocessing tokens are defined in 6.4:
> | preprocessing-token:
> | header-name
> | identifier
> | pp-number
> | character-constant
> | string-literal
> | punctuator
> | each non-white-space character that cannot be one of the above
> | [â¦]
> | White space may appear within a preprocessing token only as part of
> | a header name or between the quotation characters in a character
> | constant or string literal.
>
> So clang is wrong.
>
> It should be noted that example 4 (6.10.3.5 6) shows such a space:
>
> #define glue(a, b) a ## b
> #define xglue(a, b) glue(a, b)
>
>
> Regards,
> Clemens
Thanks Clemens for looking into the C standards.
I did more investigation before raising a new Clang bug. And actually,
the issue is more localized...
It only happen when the concatenation macro is invoked into an assembly
macro (ie: '.macro') - otherwise clang behaves as expected.
Here is the clang issue: https://llvm.org/bugs/show_bug.cgi?id=25506
--
Olivier MARTIN
http://labapart.com - Lab A Part
next prev parent reply other threads:[~2015-11-12 13:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-12 4:11 Olivier MARTIN
2015-11-12 11:17 ` Marcus Shawcroft
2015-11-12 12:39 ` Clemens Ladisch
2015-11-12 13:46 ` Olivier MARTIN [this message]
2015-11-12 14:22 ` Richard Earnshaw
2015-11-12 15:33 ` Olivier MARTIN
2015-11-12 15:50 ` Richard Earnshaw
2015-11-12 15:56 ` Olivier MARTIN
2015-11-12 15:59 ` Richard Earnshaw
2015-11-12 22:42 ` Jonathan Roelofs
2017-06-15 10:52 ` Emmanuel Blot
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