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

[Thomas Monjalon <thomas@monjalon.net>]

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


> strerror_r() not portable. An alternative can be not using it at all...

It's fine to use it.