RFR(XS): 8218935: Make jfr strncpy uses GCC 8.x friendly

[Langer, Christoph]

Hi Mikael,

lokks good to me.

In src/hotspot/share/jfr/recorder/checkpoint/types/jfrThreadGroup.cpp:
Line 242: Could you use spaces between "len+1" ? Maybe you could fix it in the line above as well...

Also assuming you update the copyright year when pushing.

Best regards
Christoph

> -----Original Message-----
> From: hotspot-jfr-dev <hotspot-jfr-dev-bounces at openjdk.java.net> On
> Behalf Of Mikael Vidstedt
> Sent: Mittwoch, 13. Februar 2019 23:54
> To: hotspot-jfr-dev at openjdk.java.net
> Cc: Dmitry Chuyko <dmitry.chuyko at bell-sw.com>
> Subject: RFR(XS): 8218935: Make jfr strncpy uses GCC 8.x friendly
> 
> 
> Please review this small fix which updates some uses of strncpy to address
> some GCC 8.x warnings.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8218935
> Webrev:
> http://cr.openjdk.java.net/~mikael/webrevs/8218935/webrev.00/open/we
> brev/
> <http://cr.openjdk.java.net/~mikael/webrevs/8218935/webrev.00/open/w
> ebrev/>
> 
> 
> Specifically, GCC 8.2 is producing warnings like this:
> 
> In function 'char* copy_path(const char*)',
>     inlined from 'void JfrChunkState::set_path(const char*)' at
> src/hotspot/share/jfr/recorder/repository/jfrChunkState.cpp:115:22:
> src/hotspot/share/jfr/recorder/repository/jfrChunkState.cpp:103:10: error:
> 'char* strncpy(char*, const char*, size_t)' output truncated before
> terminating nul copying as many bytes from a string as its length [-
> Werror=stringop-truncation]
>    strncpy(new_path, path, path_len);
>    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Basically, gcc is pointing out that the resulting string is not going to be
> terminated. This is fine from a functional perspective, because in all cases the
> very next thing we do is add the necessary nul termination, but having
> strncpy produce a nul terminated string has the benefit of not having to
> terminate it explicitly, and, of course, silence the warnings.
> 
> (Note: additional changes are needed to make the build GCC 8.2 warning
> free.)
> 
> Passes tier1.
> 
> Cheers,
> Mikael