IJ15329: RUNTIME ABORT ON THROWN EXCEPTION WHEN USING -BRTL RUNTIME LINKING

APAR status

• Closed as program error.

Error description

• An abort occurs at runtime after an exception is thrown in a
  shared library accessed via runtime linking.  The exception
  should have been caught in the library code, however the
  addition of the -brtl runtime linking option to the main
  executable causes different symbol binding to occur, and results
  in the abort.
  
  
     === TEST CASE ===
  
  // Shared Library Code
  #include <string>
  #include <stdexcept>
  void throwAndCatch() {
      try {
          std::string().substr(2);  // Triggers Exception
      } catch (const std::out_of_range &) { }
  }
  
  // Main Executable Code
  void throwAndCatch();
  
  int main() {
      throwAndCatch();
      return 0;
  }
  
     ===
  
  To Build:
  
  $ xlclang++ -qmkshrobj -o shared.so shared_library.cpp
  $ xlclang++ -Wl,-brtl main.cpp ./shared.so
  
  $ ./a.out
  IOT/Abort trap (core dumped)
  $
  
     ===
  
  Analysis of the corefile will show a reference to the
  __throw_out_of_range symbol in the cxa_demanlge component of
  libC.a:
  
  cxa_demangle.std::__1::__basic_string_common<true>::__throw_out_
  of_range() const() at 0xd243d66c
  
      (dbx) map 0xd334366c
      Entry 10:
         Object name: /usr/lib/libC.a
         Member name: shrcore.o
  
  This symbol binding is incorrect and should be bound to the
  symbol in libc++.a:
  
      Entry 3:
         Object name: /usr/lib/libc++.a
         Member name: shr.o
  

Local fix

• Do not use runtime linking.
  

Problem summary

• PROBLEM DESCRIPTION:
  A number of symbols, including __throw_out_of_range, were
  exported in the libC.a runtime library that should only be
  exported from the libc++.a runtime library.  The symbols are
  exported as weak symbols in libC.a, so normal linking works
  correctly, however runtime linking links with the incorrect
  symbols in libC.a, resulting in a runtime crash.
  
  USERS AFFECTED:
  Users compiling C++ code with the xlclang++ invocation, and
  using runtime linking (i.e. -Wl,-brtl).
  

Problem conclusion

• The incorrectly exported symbols in libC.a were removed, and
  runtime linking will now work correctly.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  XL C/C++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels