Date: Tue, 15 Mar 2016 21:50:48 +0100 From: Willem Jan Withagen <wjw@digiware.nl> To: Dimitry Andric <dimitry@andric.com> Cc: toolchain@freebsd.org Subject: Re: Crash in ostream <<operator Message-ID: <56E875A8.4090309@digiware.nl> In-Reply-To: <53A640CD-4F24-4242-8252-B27225A20071@andric.com> References: <56E7F4DB.2000404@digiware.nl> <53A640CD-4F24-4242-8252-B27225A20071@andric.com>
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On 15-3-2016 19:52, Dimitry Andric wrote:
> On 15 Mar 2016, at 12:41, Willem Jan Withagen <wjw@digiware.nl> wrote:
>>
>> While running Ceph tools I get a crash in
>> fr 10
>> #10 0x00000000016d82ca in FileStore::omap_get_values(coll_t const&, ghobject_t const&, std::__1::set<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::less<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&, std::__1::map<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, ceph::buffer::list, std::__1::less<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >, std::__1::allocator<std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const, ceph::buffer::list> > >*) ()
>> (gdb) l
>> 95 int preload_erasure_code()
>> 96 {
>> 97 string plugins = g_conf->osd_erasure_code_plugins;
>> 98 stringstream ss;
>> 99 int r = ErasureCodePluginRegistry::instance().preload(
>> 100 plugins,
>> 101 g_conf->erasure_code_dir,
>> 102 &ss);
>> 103 if (r)
>> 104 derr << ss.str() << dendl;
>> (gdb)
>> 105 else
>> 106 dout(10) << ss.str() << dendl;
>> 107 return r;
>> 108 }
>> 109
>>
>> All of this seems to be inlined since I'm not able to get at ss or r
>>
>>
>> #8 0x0000000000e16145 in std::__1::char_traits<char>::length (__s=0x0) at /usr/include/c++/v1/string:640
>> 640 static inline size_t length(const char_type* __s) {return strlen(__s);}
>
> What happened here is that something attempted to initialize a
> std::string with a NULL pointer, and that isn't allowed. As you saw in
> the debugger, the constructor just runs strlen() on the incoming string,
> and that will segfault.
>
>
>> Looking at the strlen implementation in
>> /usr/srcs/head/src/lib/libc/string/strlen.c
>>
>> shows that strlen does not take 0x0 as pointer, so when we get here with __s = 0x0 all is lost.
>> So I tried running it through 3.7, but since this is in the libraries with the bintools/os, I'd expect
>> both versions to crash on this.
>>
>> Now the question I have to solve:
>> is it the compiler/toolset/libraries
>> is it a bug in the ceph code.
>
> Most likely a bug in the Ceph code. Try figuring out where the NULL
> pointer originally came from.
I've started with compiling wit -O0 but that probably will still inline
the pieces of code designated as such. Otherwise I'll have to resort to
inserting asserts.
I'm now using gdb 7.1, loading lldb gives me a sort of strange
commandline that looks like utf-8-ish???
Would lldb give better analysis of the structures?
--WjW
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