IV85869: NAME DEMANGLING CHANGE CAUSING INCOMPATIBLE SYMBOL NAMES BETWEEN PTFS

XL C/C++ for AIX Fix Pack 16 (July 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 17 (November 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 18 (February 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 19 (August 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 20 (March 2018 Update) for 12.1
XL C/C++ for AIX Fix Pack 21 (January 2019 Update) for 12.1

APAR status

• Closed as program error.

Error description

• A C++ name mangling change to function names in unnamed
  namespaces was made in the XL C/C++ for AIX, V11.1.0.13 PTF
  (February 2013) and XL C/C++ for AIX, V12.1.0.3 PTF (March
  2013).  The V11.1 APAR was IV24703, and the V12.1 APAR was
  IV37942.
  
  This change introduced a backwards compatibility issue with code
  compiled before/after the fix.  Linking objects compiled with
  the compiler before the fix with objects compiled after the fix
  might result in undefined symbol linker errors for similar
  function names in unnamed namespaces.
  
  This APAR is to revert the name mangling behaviour change in
  IV24703 and IV37942 to allow the older behaviour to act as
  default.  The newer IV24703 and IV37942 behaviour will now be
  enabled by a -qxflag option, and will be required by users
  impacted by the constructor/destructor issue as described in
  IV24703 and IV37942.
  
  The newer IV24703 and IV37942 behaviour is enabled by default in
  the V13.1 and up compilers.  Older name mangling behaviour can
  be set with the -qnamemangling option.
  
  
  
     === TEST CASE ===
  
  For objects compiled with
      V11.1.0.0 - V11.1.0.12 / V12.1.0.0 -V12.1.0.2:
  
  $ cat test.cpp
  namespace {
      int testfunc() { return 5; }
  }
  $ xlC -c test.cpp
  $ nm -C test.o | grep testfunc
  .testfunc__10test.cpp-0Fv T         320
  testfunc__10test.cpp-0Fv D         952          12
  testfunc__10test.cpp-0Fv d         916           4
  $
  
  For objects compiled with
      V11.1.0.13 - V11.1.0.23 / V12.1.0.3 - V12.1.0.15:
  
  $ xlC -c test.cpp
  bash-4.2$ nm test.o | grep testfunc
  .testfunc__8test_cppFv T         320
  testfunc__8test_cppFv D         952          12
  testfunc__8test_cppFv d         916           4
  $
  

Local fix

• None.  Use older PTF level to generate older name mangling
  behaviour.
  

Problem summary

• PROBLEM DESCRIPTION:
  The problem is with inconsistent mangling of
  constructor/destructor names for classes in an unnamed
  namespace between PTF releases.
  
  USERS AFFECTED:
  The problem may affect users of a class in an unnamed namespace
  requiring binary compatibility with an older compiler.
  

Problem conclusion

• The original V11.1/V12.1 name mangling has been restored and
  the updated mangling is protected under a special flag:
  -qxflag=UnnamedNamespaceNM
  

Temporary fix

Comments

APAR Information

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

  IV82949

• 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

• RC10 PSY

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