Re: [Qemu-devel] [PATCH] error: error_setg_errno(): errno gets preserved

[Sascha Silbe <silbe@linux.vnet.ibm.com>]

Dear Eric,

Eric Blake <eblake@redhat.com> writes:

>> +++ b/include/qapi/error.h
>> @@ -170,6 +170,9 @@ void error_setg_internal(Error **errp,
>>   * Just like error_setg(), with @os_error info added to the message.
>>   * If @os_error is non-zero, ": " + strerror(os_error) is appended to
>>   * the human-readable error message.
>> + *
>> + * The value of errno (which usually can get clobbered by almost any
>> + * function call) will be preserved.
>>   */
>>  #define error_setg_errno(errp, os_error, fmt, ...)                      \
>>      error_setg_errno_internal((errp), __FILE__, __LINE__, __func__,     \
>
> Do we need/want to make the guarantee of preserving errno across any of
> the other functions and macros declared in error.h?

It would be more consistent to have all error reporting functions
promise this, even if they do not get passed the errno. In some cases
the errno might not matter to the user (so error_setg_errno() isn't
used), but still be passed on to the caller to signal an error (so
clobbering it could be problematic).

Can prepare a follow-up patch that makes sure error_setg(),
error_propagate(), error_setg_file_open(), error_set() preserve
errno. Optionally also the other functions listed in
include/qapi/error.h and include/qemu/error-report.h.

Sascha
-- 
Softwareentwicklung Sascha Silbe, Niederhofenstraße 5/1, 71229 Leonberg
https://se-silbe.de/
USt-IdNr. DE281696641