PH66223: METAL C MEMCMP() GENERATES INCORRECT ASSEMBLER INSTRUCTIONS COMPARING SAME VALUES

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When using the memcmp() function in the following testcase:
  1     #include <metal.h>
      2     #include <string.h>
      3     #include <stdio.h>
      4
      5     int compare(const void * num1, const void * num2) {
      6          int val= memcmp(&num1, &num2, sizeof(num1));
      7          return val;
      8     }
  
  
  Compiling for Metal C and generating assembler source:
  >xlc -S -qmetal -qlist -qsource
  -Wc,"NOSEARCH,SEARCH(/usr/include/metal)" test.c >test.lst
  >as -a=test.asmlst test.s
  
  If using references "&" to the address in the pointer, comparing
  &num1 and &num1, the following assembler gets generated for
  memcmp() function:
  
     99                                                 36 *  int
  val= memcmp(&num1, &num2, sizeof(num1));
   000006
    100   0000004A 58E0 D070               00000070     37
   L     14,112(,13)             #SR_PARM_1
  000006
    101   0000004E E54C D054 0000 00000054              38
   MVHI  84(13),0
  000006
    102                       R:E 00000000              39
   USING @@PARMD@1,14
  000006
    103   00000054 41F0 E004               00000004     40
   LA    15,@3num2
  000006
    104                                                 41
   DROP  14
  000006
    105                       R:F 00000000              42
   USING @@PARMD@1,15
  000006
    106   00000058 D503 F000 F000 00000000 00000000     43
   CLC   @2num1,@3num2-4
  000006
  
  The CLC seems to compare the same R15 and not R14 with R15:
    106   00000058 D503 F000 F000 00000000 00000000     43
   CLC   @2num1,@3num2-4
  000006
  

Local fix

• If you use a pointer value in the memcmp() function it should
  generate the CLC correctly to compare R14 and R15:
      6          int val= memcmp(num1, num2, sizeof(num1));
  
  >xlc -S -qmetal -qlist -qsource
  -Wc,"NOSEARCH,SEARCH(/usr/include/metal)" test.c >test.lst
  >as -a=test.asmlst test.s
    105   0000005C D503 E000 F000 00000000 00000000     42
   CLC   0(4,14),0(15)
  000006
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of metal C with generated SS or SSE    *
  *                 instruction format instruction, where both   *
  *                 address operands are directly from the       *
  *                 parameters save area.                        *
  ****************************************************************
  * PROBLEM DESCRIPTION: Incorrect assembly code might be        *
  *                      generated for metal C program with      *
  *                      generated SS or SSE instruction format  *
  *                      instruction, where both address         *
  *                      operands are directly from the          *
  *                      parameters save area.                   *
  ****************************************************************
  * RECOMMENDATION: install the PTF                              *
  ****************************************************************
  N/A
  

Problem conclusion

• install the PTF
  

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:

  UO03571

Modules/Macros

• CCNECICS CCNECWI  CCNED240 CCNEDSCT CCNEDWRT CCNEFILT CCNEHIFC
  CCNEIPA3 CCNEIPAO CCNEMDEP CCNEOPTP CCNEP    CCNEPP   CCNETBY
  CCNMSGE  CCNMSGT  CCNQIPA
  

Fix information

• Fixed component name

  C/C++ FOR MVS

• Fixed component ID

  56551210A

Applicable component levels

• R7C0 PSY UO03571

     UP25/07/30 P F507

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.