PI92943: INCORRECT C++ CALLING CONVENTION FOR DEREFERENCED COMPLEX-TYPE STRUCT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The October 2017 z/OS XL C/C++ V2R2 PTF contained APAR PI88204
  which corrected a C++ calling convention issue for structs
  containing two floating point values (i.e. the 'complex'
  datatype).  The fix corrected the parameter-passing method for
  this type, i.e. via floating point registers instead of general
  purpose registers.
  
  This APAR corrects a similar case where a dereferenced 'complex'
  struct is passed to a function.
  
  
     === TEST CASE ===
  #include <stdio.h>
  
  struct Complex
  {
      double real;
      double imag;
  };
  
  void func( struct Complex t )
  {
      printf( "%10f , %10f \n", t.real, t.imag );
  }
  
  int main( int ac, char *av[] )
  {
      struct Complex st;
      struct Complex *p_st = &st;
      st.real = 1.1;
      st.imag = 2.2;
  
      func( p_st[0] );  // PASSING DEREFERENCED STRUCT
      func( *p_st   );
  
      return 0;
  }
  
  $ xlc++ -q64 -qlist apar.cpp
  
  
     === LISTING ===
  
            func(Complex)
  000009 |        DS       0D
  000009 |        STMG     r5,r9,1736(r4)
  000009 |        LAY      r4,-320(,r4)
  End of Prolog
  
  000000 |        LARL     r9,F'118'
  000009 |        STD      f0,t(,r4,2496)  // LOAD VALUES IN
  000009 |        STD      f2,t(,r4,2504)   // VIA FPRs
  
  
            main()
  000014 |        STMG     r5,r9,1736(r4)
  000014 |        LAY      r4,-320(,r4)
   000114           End of Prolog
  
  000000 |        LARL     r9,F'62'
  ...
  000021 |       *  func( p_st[0]);
  000021 |        LG       r6,p_st(,r4,2240)
  000021 |        LG       r5,#Save_ADA_Ptr_2(,r4,2056)
  000021 |        LG       r1,(Complex)(,r6,0)   // LOAD VALUES IN
  000021 |        LG       r2,(Complex)(,r6,8)    // VIA GPRs
  000021 |        BRAS     r7,func(Complex)
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: C++ users calling function with homogeneous  *
  *                 float aggregate parameter like 'complex' by  *
  *                 indirecting argument(s).                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: Indirecting argument used general       *
  *                      purpose registers are apposed to        *
  *                      floating registers but the function     *
  *                      was                                     *
  *                      receiving argument via floating point   *
  *                      registers. This caused incorrect        *
  *                      floating point values.                  *
  ****************************************************************
  .
  

Problem conclusion

• Apply service provided.
  

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:

  PI96208

Modules/Macros

• CCNECICS CCNECWI  CCNED220 CCNEDSCT CCNEDWRT CCNEFILT CCNEHIFC
  CCNEMDEP CCNEOPTP CCNEP    CCNEPP   CCNETBY  CCNMSGE  CCNMSGT
  

Fix information

• Fixed component name

  C/C++ FOR MVS

• Fixed component ID

  56551210A

Applicable component levels

• R7A0 PSY UI53925

     UP18/03/15 P F803

Fix is available

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