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https://issues.apache.org/jira/browse/TS-837?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13065973#comment-13065973
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Alan M. Carroll commented on TS-837:
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I spent over a day working on this when I ran it to it and the problem is much
larger than just this one place. I found no end to similar issues and in at
least one case (casting between sockaddr types in ink_inet.h) no reasonable
solution[1]. I think it is insolvable without changes to the compiler or the
language specification[2]. The best that can be done is the work around of
using -fno-strict-aliasing as a gcc option.
I do have a solution to this specific issue which I will check in because
(IMHO) it's cleaner, better code, and another couple fixes on this same theme.
Those are just a drop in the bucket of the underlying issue, however (see
I_ProxyAllocator.h for another nasty instance).
[1] It does seem possible to work around if you declare a local uint64_t and
assign in to and out of it. The variable is required, just casting through
uint64_t doesn't suffice. The Unix paradigm for network address handling is
critically dependent on exactly that type of type punning which makes a work
around challenging at best.
[2] My suggestion would be a monad like "volatile" which means "this pointer is
potentially aliasing / aliased by another pointer" and prevents optimizations,
just like volatile does.
> ATS fails to compile with gcc 4.6.1 with --enable-debug
> -------------------------------------------------------
>
> Key: TS-837
> URL: https://issues.apache.org/jira/browse/TS-837
> Project: Traffic Server
> Issue Type: Bug
> Affects Versions: 3.1.0, 3.0.0
> Environment: Linux, Debian, Amd64 + GCC 4.6.1
> Reporter: Igor Galić
> Fix For: 3.1.0
>
>
> {noformat}
> In file included from ../../proxy/ControlMatcher.h:104:0,
> from ../../proxy/ParentSelection.h:37,
> from P_Socks.h:30,
> from P_Net.h:106,
> from Connection.cc:34:
> ../../proxy/hdrs/HTTP.h: In member function 'INK_MD5
> HTTPInfo::object_key_get()':
> ../../proxy/hdrs/HTTP.h:1375:24: error: dereferencing type-punned pointer
> will break strict-aliasing rules [-Werror=strict-aliasing]
> ../../proxy/hdrs/HTTP.h: In member function 'int64_t
> HTTPInfo::object_size_get()':
> ../../proxy/hdrs/HTTP.h:1405:24: error: dereferencing type-punned pointer
> will break strict-aliasing rules [-Werror=strict-aliasing]
> ../../proxy/hdrs/HTTP.h: In member function 'void
> HTTPInfo::object_size_set(int64_t)':
> ../../proxy/hdrs/HTTP.h:1422:51: error: dereferencing type-punned pointer
> will break strict-aliasing rules [-Werror=strict-aliasing]
> cc1plus: all warnings being treated as errors
> *** [Connection.o] Error 1
> make[2]: Leaving directory `/netsrc/trafficserver-3.0.0/iocore/net'
> make[1]: *** [all-recursive] Error 1
> make[1]: Leaving directory `/netsrc/trafficserver-3.0.0/iocore'
> make: *** [all-recursive] Error 1
> {noformat}
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