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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Re: warnings about strict aliasing |
| From: | Dirk Zimoch <[email protected]> |
| To: | Michael Davidsaver <[email protected]>, "[email protected]" <[email protected]> |
| Date: | Thu, 30 Nov 2017 13:33:39 +0100 |
On 29.11.2017 20:51, Michael Davidsaver wrote:
On 11/29/2017 12:43 PM, Dirk Zimoch wrote:The file anyscalar.h generates many warnings of the form /afs/psi.ch/group/8431/dirk/git/BASE/epics-base-master/include/pv/anyscalar.h:98: warning: dereferencing pointer ‘<anonymous>’ does break strict-aliasing rulesThe construct used (std::aligned_storage) is well defined in c++11. http://en.cppreference.com/w/cpp/types/aligned_storageI am a bit concerned about that because it may lead to wrong optimization. I think this should either be fixed or -fno-strict-aliasing should be added to the compiler flags for recent gccs (i.e. not old vxWorks :-) )GCC >=4.8.4 (at latest) doesn't warn about this even with -std=c++98. So if anything, this is only need for older compilers.
I checked the code and found that older compilers (those who complain) see a different piece of code. (#if __cplusplus>=201103L ... #else). And not all of them complain.
I will do some tests to find out if I can remove the warnings. If not, I will add the -fno-strict-aliasing compiler option to my architectures which use older compilers and to the vxWorks configuration in EPICS.
But this is no showstopper for the release.