[llvm-bugs] [Bug 33846] New: extern thread_local and lto

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Jul 18 21:13:34 PDT 2017 

https://bugs.llvm.org/show_bug.cgi?id=33846

            Bug ID: 33846
           Summary: extern thread_local and lto
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: anthony at ajrh.net
                CC: llvm-bugs at lists.llvm.org

compiling the following into a shared library:

__attribute__ ((visibility("default"))) extern thread_local int foo;
int x() { return foo; }

generates TLS support functions:

% clang++ -std=c++11 -fPIC -shared  -o x.so z.cpp && nm x.so | c++filt | grep
TLS
                 w TLS init function for foo
00000000000006c0 t TLS wrapper function for foo

which vanish if -flto is used:

% clang++ -flto -std=c++11 -fPIC -shared  -o x.so z.cpp && nm x.so | c++filt |
grep TLS
                 U TLS init function for foo

=========================================
this is with current Debian testing distribution, per below

% clang++ -v -flto -std=c++11 -fPIC -shared  -o x.so z.cpp
clang version 4.0.1-1 (tags/RELEASE_401/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.2
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.2.4
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.3.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.5.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.2.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.3.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.5.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.1.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
 "/usr/lib/llvm-4.0/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-llvm-bc
-flto -disable-free -disable-llvm-verifier -discard-value-names -main-file-name
z.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix
-mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases
-munwind-tables -fuse-init-array -target-cpu x86-64 -v -dwarf-column-info
-debugger-tuning=gdb -resource-dir /usr/lib/llvm-4.0/bin/../lib/clang/4.0.1
-internal-isystem
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/c++/7.1.0
-internal-isystem
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/x86_64-linux-gnu/c++/7.1.0
-internal-isystem
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/x86_64-linux-gnu/c++/7.1.0
-internal-isystem
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/c++/7.1.0/backward
-internal-isystem /usr/include/clang/4.0.1/include/ -internal-isystem
/usr/local/include -internal-isystem
/usr/lib/llvm-4.0/bin/../lib/clang/4.0.1/include -internal-externc-isystem
/usr/include/x86_64-linux-gnu -internal-externc-isystem /include
-internal-externc-isystem /usr/include -std=c++11 -fdeprecated-macro
-fdebug-compilation-dir /work/ajrh/src/etp/src -ferror-limit 19
-fmessage-length 168 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions
-fdiagnostics-show-option -fcolor-diagnostics -o /tmp/z-8e3cb3.o -x c++ z.cpp
clang -cc1 version 4.0.1 based upon LLVM 4.0.1 default target
x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
ignoring duplicate directory
"/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/x86_64-linux-gnu/c++/7.1.0"
ignoring duplicate directory "/usr/include/clang/4.0.1/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/c++/7.1.0

/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/x86_64-linux-gnu/c++/7.1.0

/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../../include/c++/7.1.0/backward
 /usr/include/clang/4.0.1/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
 "/usr/bin/ld" --eh-frame-hdr -m elf_x86_64 -shared -o x.so
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../x86_64-linux-gnu/crti.o
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/crtbeginS.o
-L/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0
-L/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../x86_64-linux-gnu
-L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
-L/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../..
-L/usr/lib/llvm-4.0/bin/../lib -L/lib -L/usr/lib -plugin
/usr/lib/llvm-4.0/bin/../lib/LLVMgold.so -plugin-opt=mcpu=x86-64
/tmp/z-8e3cb3.o -lstdc++ -lm -lgcc_s -lc -lgcc_s
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/crtendS.o
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.1.0/../../../x86_64-linux-gnu/crtn.o

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