From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ferruh Yigit <ferruh.yigit@intel.com>
Subject: Re: [PATCH] eal: fix API to get error string
Date: Wed, 31 Oct 2018 18:26:07 +0000
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 <5469782.njCRi2Lb0J@xps>
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Cc: dev@dpdk.org, Bruce Richardson <bruce.richardson@intel.com>,
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To: Thomas Monjalon <thomas@monjalon.net>
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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.