From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19182 invoked by alias); 20 Jan 2015 19:16:23 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 19156 invoked by uid 48); 20 Jan 2015 19:16:18 -0000 From: "vhaisman at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/64697] New: C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd' Date: Tue, 20 Jan 2015 19:16:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 4.9.2 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: vhaisman at gmail dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2015-01/txt/msg02097.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697 Bug ID: 64697 Summary: C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd' Product: gcc Version: 4.9.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: vhaisman at gmail dot com I have hit an issue with thread-local storage variables on Cygwin/AMD64, I do not see it with Cygwin/i686. I am having linking issues when using `thread_local` keyword in Cygwin with its GCC 4.8.3 and GCC 4.9.2. This is derived from log4cplus. The test case is split into three files: File def.hxx: ~~~~ #include namespace N { struct S { std::string str; }; // extern declaration in a header extern thread_local S * ptd; // accessing the extern declared ptd here inline S * get_ptd () { if (! ptd) ptd = new S; return ptd; } } // namespace N ~~~~ File def.cxx: ~~~~ #include "def.hxx" namespace N { // definition of ptd thread_local S * ptd = nullptr; } // namespace N ~~~ File use.cxx: ~~~~ #include "def.hxx" namespace N { __declspec(dllexport) void * foo () { // invoking inline get_ptd() function to get the value in ptd return get_ptd (); } } ~~~~ Now, when I compile each .cxx with `g++ -std=gnu++11 -fvisibility=hidden -c use.cxx def.cxx` and then try to link with `g++ -shared -o cygtest.dll use.o def.o`, I get the following error from linker: ~~~~ use.o:use.cxx:(.text$_ZTWN1N3ptdE[_ZTWN1N3ptdE]+0x15): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd' collect2: error: ld returned 1 exit status ~~~~ The nm -C ./def.o output confirms that: ~~~~ `--> nm -C ./def.o 0000000000000000 b .bss 0000000000000000 d .data 0000000000000000 r .rdata 0000000000000000 r .rdata$zzz 0000000000000000 t .text 0000000000000008 r __emutls_t._ZN1N3ptdE 0000000000000000 D __emutls_v._ZN1N3ptdE 0000000000000000 r std::piecewise_construct ~~~~ As you can see, the ptd thread-local variable initialization function is not defined anywhere. The use.o references this initialization function (see bottom of the listing): ~~~~ `--> nm -C ./use.o 0000000000000000 b .bss 0000000000000000 d .data 0000000000000000 i .drectve 0000000000000000 p .pdata 0000000000000000 p .pdata$_ZN1N1SC1Ev 0000000000000000 p .pdata$_ZN1N7get_ptdEv 0000000000000000 p .pdata$_ZTWN1N3ptdE 0000000000000000 r .rdata 0000000000000000 r .rdata$.refptr.__emutls_v._ZN1N3ptdE 0000000000000000 r .rdata$.refptr._ZTHN1N3ptdE 0000000000000000 r .rdata$zzz 0000000000000000 R .refptr.__emutls_v._ZN1N3ptdE 0000000000000000 R .refptr._ZTHN1N3ptdE 0000000000000000 t .text 0000000000000000 t .text$_ZN1N1SC1Ev 0000000000000000 t .text$_ZN1N7get_ptdEv 0000000000000000 t .text$_ZTWN1N3ptdE 0000000000000000 A .weak._ZTHN1N3ptdE._ZN1N1SC1Ev 0000000000000000 r .xdata 0000000000000000 r .xdata$_ZN1N1SC1Ev 0000000000000000 r .xdata$_ZN1N7get_ptdEv 0000000000000000 r .xdata$_ZTWN1N3ptdE U __emutls_get_address U __emutls_v._ZN1N3ptdE U __gxx_personality_seh0 U __real__ZdlPv U __real__Znwm U _Unwind_Resume U operator delete(void*) 0000000000000000 T N::S::S() 0000000000000000 T N::foo() 0000000000000000 T N::get_ptd() U std::basic_string, std::allocator >::basic_string() U operator new(unsigned long) 0000000000000000 r std::piecewise_construct w TLS init function for N::ptd 0000000000000000 T TLS wrapper function for N::ptd ~~~~ Now, this code seems to work well on Linux with both GCC and Clang. Is this a GCC problem on Cygwin? Am I using extern thread_local wrong? My experiments show that not using the extern keyword seems to fix the issue. But I am not sure if that does not introduce two ptd thread-local variables in two TUs. See also http://stackoverflow.com/q/28023728/341065