Am 2015-06-11 10:09, schrieb Richard Weinberger:
> On Thu, Jun 11, 2015 at 9:54 AM, Hans-Werner Hilse <[email protected]>
> wrote:
>> About forbidden use of names/identifiers from the stdlib, the C
>> standard
>> is a bit hard for me to grasp fully. However, I think C99 7.1.3
>> paragraph 1, 3rd point is relevant here: "Each macro name in any of
>> the
>> following subclauses (including the future library directions) is
>> reserved for use as specified if any of its associated headers is
>> included; unless explicitly stated otherwise (see 7.1.4)."
>
> Yeah, but we're talking about structure members.
Indeed, and I can't find more detail about the "reserved for use as
specified" part.
I think it is saying, though, that those identifiers are macros (and as
such will get expanded). The preprocessor will not care if that's in a
struct member name.
>> So aside from renaming struct members, another option would be to lift
>> the macro definition by an "#undef" in relevant places. I have a
>> feeling, though, that this faces new problems with the C99 standard,
>> 7.1.3 paragraph 3, which says that "If the program removes (with
>> #undef)
>> any macro definition of an identifier in the first group listed above,
>> the behavior is undefined."
>
> So, what exactly is the build error you're facing and how can I
> reproduce?
Of course I should have told you in the first place:
[hw@hilses linux-uml]$ make ARCH=um CC="musl-gcc"
...
CC arch/um/drivers/slip_user.o
In file included from arch/um/drivers/slip_user.c:12:0:
/usr/lib/musl/include/sys/termios.h:1:2: warning: #warning redirecting
incorrect #include <sys/termios.h> to <termios.h> [-Wcpp]
#warning redirecting incorrect #include <sys/termios.h> to <termios.h>
^
In file included from arch/um/drivers/slip_user.c:6:0:
arch/um/drivers/slip_user.c: In function ‘slip_pre_exec’:
arch/um/drivers/slip_user.c:67:12: error: expected identifier before ‘(’
token
if (data->stdin >= 0)
^
arch/um/drivers/slip_user.c:68:14: error: expected identifier before ‘(’
token
dup2(data->stdin, 0);
^
arch/um/drivers/slip_user.c:68:3: error: too few arguments to function
‘dup2’
dup2(data->stdin, 0);
^
(We can ignore the warning for now/this discussion, I think.)
You can reproduce without actually installing a musl toolchain when
changing glibc's macro definition to musl's:
make ARCH=um CFLAGS="-Dstdout=\\(stdout\\)"
Will trigger the same error in the same place. Of course, this is
artificially producing it. Using musl, however, leads to the same
behaviour.
I used the defconfig, that's why it triggers in slip_user.c first -
other places do use stdin/stdout as struct member name, too.
-hwh
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