Re: [PATCH v2] Do not use %m in common code to print error messages

[Thomas Huth <thuth@redhat.com>]

On 18/10/2019 15.49, Kamil Rytarowski wrote:
> On 18.10.2019 15:42, Stefano Garzarella wrote:
>> On Fri, Oct 18, 2019 at 03:07:16PM +0200, Thomas Huth wrote:
>>> The %m format specifier is an extension from glibc - and when compiling
>>> QEMU for NetBSD, the compiler correctly complains, e.g.:
>>>
>>> /home/qemu/qemu-test.ELjfrQ/src/util/main-loop.c: In function 'sigfd_handler':
>>> /home/qemu/qemu-test.ELjfrQ/src/util/main-loop.c:64:13: warning: %m is only
>>>  allowed in syslog(3) like functions [-Wformat=]
>>>              printf("read from sigfd returned %zd: %m\n", len);
>>>              ^
>>> Let's use g_strerror() here instead, which is an easy-to-use wrapper
>>> around the thread-safe strerror_r() function.
>>>
>>> While we're at it, also convert the "printf()" in main-loop.c into
>>> the preferred "error_report()".
>>>
>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>> ---
>>>  v2: Do not try to g_free() the strings
>>>
>>>  hw/misc/tmp421.c | 4 ++--
>>>  util/main-loop.c | 3 ++-
>>>  util/systemd.c   | 4 ++--
>>>  3 files changed, 6 insertions(+), 5 deletions(-)
>>
>> There are many uses of %m also in hw/vfio/ but that's Linux stuff.
>> Should we change those too or it doesn't matter since it never really
>> compiled on NetBSD?
> 
> It's a gnu (glibc) extension and linux can use alternative libc
> implementations. Probably most of them capable to host qemu use %m.

I think I read somewhere that other libcs on Linux also support %m (like
musl), but I just can't find that reference anymore. Anyway, we can
still fix that later in case someone hits the issue.

>> Anyway, this patch LGTM:
>> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

 Thanks,
  Thomas