LI77335: ?: METHOD PARAMETER OPTIMIZING AWAY VALID CODE

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • Compiling with -O2 and inlining enabled, with a ?: conditional
    as a template function parameter, is causing valid code to be
    optimized away, resulting in invalid code behaviour.  In the
    example below, invalid stack data is accessed, and output is
    incorrect:
    
    
        ====  TEST CASE  ====
    
    #include <iostream>
    
    struct MyStruct
    {
        template <typename T>
        static void print( T const & x )
        {
            std::cout << x;
        }
    };
    
    int main(int argc, char *argv[])
    {
      MyStruct::print(argc == 1?"test1":"test2");
    }
    
    
    $ xlC -q64 -O2 apar.cpp
    $ ./a.out | od -c
    0000000  &#65447; &#65434; 017   &#65413; &#65517; &#65488; \r &#65447; &#65434; 017   &#65413;   &#65517; &#65488;  \r
    0000020
    $
    $ ./a.out | od -x
    0000000  badc 0ffe e0dd f00d badc 0ffe e0dd f00d
    0000020
    $
    

Local fix

  • - Disable inlining
    - Convert ?: conditional into an IF statement
    

Problem summary

  • PROBLEM DESCRIPTION:
    Processing of the ?: ternary operator is ignoring the memory
    location of the result, leading to incorrect code and
    behaviour.
    
    USERS AFFECTED:
    Users of the ?: ternary operator, the << operator, and
    optimization.
    

Problem conclusion

  • The issue has been corrected.
    

Temporary fix

Comments

APAR Information

  • APAR number

    LI77335

  • Reported component name

    XL C/C++ FOR LI

  • Reported component ID

    5725C7300

  • Reported release

    C10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-04-27

  • Closed date

    2013-04-27

  • Last modified date

    2013-04-27

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

    IV31404

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

Fix information

  • Fixed component name

    XL C/C++ FOR LI

  • Fixed component ID

    5725C7300

Applicable component levels



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Document information


More support for:

XL C/C++ for Linux
Compiler

Software version:

12.1

Reference #:

LI77335

Modified date:

2013-04-27

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