This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH 1/6] Add INLINE_SYSCALL_ERROR_RETURN
- From: Florian Weimer <fweimer at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 13 Oct 2015 15:01:28 +0200
- Subject: Re: [PATCH 1/6] Add INLINE_SYSCALL_ERROR_RETURN
- Authentication-results: sourceware.org; auth=none
- References: <20151012231925 dot GB17339 at intel dot com> <561CFB56 dot 1050504 at redhat dot com> <CAMe9rOqQW4QJiTJkOp5zUfENeDNnxHiBG3OvjGJ867u4eG52cQ at mail dot gmail dot com>
On 10/13/2015 02:44 PM, H.J. Lu wrote:
> On Tue, Oct 13, 2015 at 5:38 AM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 10/13/2015 01:19 AM, H.J. Lu wrote:
>>> +/* Set error number and return -1. A target may choose to return the
>>> + internal function, __syscall_error, which sets errno and returns -1. */
>>> +#define INLINE_SYSCALL_ERROR_RETURN(err) \
>>> + ({ \
>>> + __set_errno (err); \
>>> + -1; \
>>> + })
>>
>> I think the name is unfortunate because it the macro does not contain a
>> return statement.
>>
>> Perhaps INLINE_SYSCALL_SET_ERRNO would be a better name?
>>
>> Florian
>
> i386 defines it as
>
> /* Set error number and return -1. Return the internal function,
> __syscall_error, which sets errno from the negative error number
> and returns -1, to avoid PIC. */
> #undef INLINE_SYSCALL_ERROR_RETURN
> #define INLINE_SYSCALL_ERROR_RETURN(resultvar) \
> __syscall_error (-(resultvar))
>
> This macro should only be used with "return".
> INLINE_SYSCALL_SET_ERRNO may be misleading.
> How about INLINE_SYSCALL_SET_ERRNO_AND_RETURN?
Same problem, the macro does not actually return or alter control flow
in any way. INLINE_SYSCALL_SET_ERRNO_IN_TAIL or
INLINE_SYSCALL_SET_ERRNO_AT_TAIL would be more appropriate.
You could turn the generic definition into an inline function an use the
__wur attribute, then misuse would be easier to detect. The comment on
the declaration should point users who use this function for side effect
only to __set_errno.
Florian