Re: [dpdk-stable] [dpdk-dev] [PATCH] eal: fix API to get error string

[Thomas Monjalon <thomas@monjalon.net>]

01/11/2018 13:46, Ferruh Yigit:
> On 10/31/2018 6:43 PM, Thomas Monjalon wrote:
> > 31/10/2018 19:26, Ferruh Yigit:
> >> On 10/31/2018 6:26 PM, Ferruh Yigit wrote:
> >>> On 10/31/2018 5:16 PM, Thomas Monjalon wrote:
> >>>> 31/10/2018 18:19, Ferruh Yigit:
> >>>>> rte_strerror uses strerror_r(), and strerror_r() has two version of it.
> >>>>> - XSI-compliant version, (_POSIX_C_SOURCE >= 200112L) && !  _GNU_SOURCE
> >>>>> - GNU-specific version
> >>>>>
> >>>>> Those two has different return types, so the exiting return type check
> >>>>> is not correct for GNU-specific version.
> >>>>>
> >>>>> And this is causing failure in errno_autotest unit test.
> >>>>>
> >>>>> Adding different implementation for FreeBSD and Linux.
> >>>>>
> >>>>> Fixes: 016c32bd3e3d ("eal: cleanup strerror function")
> >>>>> Cc: stable@dpdk.org
> >>>>>
> >>>>> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> >>>>> ---
> >>>>> --- a/lib/librte_eal/common/eal_common_errno.c
> >>>>> +++ b/lib/librte_eal/common/eal_common_errno.c
> >>>>>  		default:
> >>>>> +#ifdef RTE_EXEC_ENV_BSDAPP
> >>>>>  			if (strerror_r(errnum, ret, RETVAL_SZ) != 0)
> >>>>>  				snprintf(ret, RETVAL_SZ, "Unknown error%s %d",
> >>>>>  						sep, errnum);
> >>>>> +#else
> >>>>> +			/*
> >>>>> +			 * _GNU_SOURCE version, error string is not always
> >>>>> +			 * strored in "ret" buffer, need to use return value
> >>>>> +			 */
> >>>>> +			ret = strerror_r(errnum, ret, RETVAL_SZ);
> >>>>> +#endif
> >>>>
> >>>> Why not use the return value in both cases?
> >>>>
> >>>> Why not writing an error message in Linux case?
> >>>
> >>> "man strerror_r" has more details, but briefly,
> >>>
> >>> The XSI-compliant strerror_r() function returns 0 on success. GNU one returns
> >>> the pointer to string.
> >>>
> >>> The XSI-compliant can return an empty buffer, GNU one always return a string,
> >>> either proper error string or "Unknown .." one.
> > 
> > You say "GNU one always return a string"
> > The comment says:
> > _GNU_SOURCE version, error string is not always strored in "ret" buffer
> 
> Yes, GNU one always return a char pointer to a string but that pointer may not
> be in the "ret" buffer.

OK

So I suggest only 2 minor changes:
	- strored -> stored
	- add a comment to explain that the error message from return value is enough

> >> strerror_r() not portable. An alternative can be not using it at all...
> > 
> > It's fine to use it.