[Openmp-commits] [PATCH] D93727: [OpenMP] Add using bit flags to select Libomptarget Information

[Joseph Huber via Phabricator via Openmp-commits]

jhuber6 added inline comments.


================
Comment at: openmp/libomptarget/include/Debug.h:54-63
+static inline uint32_t getInfoLevel() {
+  static uint32_t InfoLevel = 0;
+  static std::once_flag Flag{};
+  std::call_once(Flag, []() {
+    if (char *EnvStr = getenv("LIBOMPTARGET_INFO"))
+      InfoLevel = std::stoi(EnvStr);
+  });
----------------
jhuber6 wrote:
> vzakhari wrote:
> > Hello.  Am I the only one who is getting `libomptarget.rtl.x86_64.so` build fail with `-DCMAKE_BUILD_TYPE=Debug`?
> > 
> > > ld: CMakeFiles/omptarget.rtl.x86_64.dir/__/generic-elf-64bit/src/rtl.cpp.o: in function `getInfoLevel()::{lambda()#1}::operator()() const':
> > > .../openmp/libomptarget/include/Debug.h:61: undefined reference to `getInfoLevel()::InfoLevel'
> > > ld: CMakeFiles/omptarget.rtl.x86_64.dir/__/generic-elf-64bit/src/rtl.cpp.o: relocation R_X86_64_PC32 against undefined symbol `_ZZL12getInfoLevelvE9InfoLevel' can not be used when making a shared object; recompile with -fPIC
> > 
> > Here is a small reproducer:
> > 
> > ```
> > #include <mutex>
> > 
> > static inline uint32_t getInfoLevel() {
> >   static uint32_t InfoLevel = 0;
> >   static std::once_flag Flag{};
> >   std::call_once(Flag, []() {
> >       InfoLevel = 1;
> >   });
> > 
> >   return InfoLevel;
> > }
> > ```
> > 
> > I cannot build a shared library from it using gcc: g++ -fPIC -std=c++14 test.cpp -shared -o test.so
> > 
> > 
> > > ld: /tmp/ccBpTXXs.o: relocation R_X86_64_PC32 against undefined symbol `_ZZL12getInfoLevelvE9InfoLevel' can not be used when making a shared object; recompile with -fPIC
> > 
> > 
> > The issue is reproducible with GCC 5.5.0 and 6.5.0, and does not reproduce with 7.3.0.  I believe LLVM's minimal requirement is 5.1, so it is a problem.
> > 
> > The issue seems to be caused by the fact that getInfoLevel() is not referenced in `openmp/libomptarget/plugins/generic-elf-64bit/src/rtl.cpp`
> I have no issues compiling the reproducer you provided. It compiles without errors locally and here https://godbolt.org/z/oEKq3E for the compilers you listed. There might be a problem when the compiler doesn't create a static variable when the function in unused. Does the problem go away if you create a dummy usage of getInfoLevel()?
Actually you're right, it doesn't work on Godbolt, the error went off screen and didn't list as an error in the compilation. It definitely works locally on the machine I tested it on so who knows what's up with that. The error goes away if I just add a dummy usage to force the compiler to actually generate a symbol for InfoLevel. It's a solution but probably not the best.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93727/new/

https://reviews.llvm.org/D93727