Documentation errata for IBM XL C/C++ for Linux, V12.1

Preventive Service Planning


Abstract

This page contains corrections and additions to the product documentation shipped with IBM XL C/C++ for Linux, V12.1.

Content

Installation Guide
The following corrections and additions apply to the IBM XL C/C++ for Linux, V12.1 Installation Guide:

Topic location: Before installing IBM XL C/C++ for Linux, V12.1

Upgrading the evaluation copy of the XL C/C++ compiler

Install only the vac.lic RPM packages for the full product version of the XL C/C++ compiler and run vac_configure to re-configure the compiler.

Should read:

  1. Install the vac.lic RPM packages.

  2. Install the vac.cmp and vacpp.cmp RPM packages using the --replacepkgs --replacefiles options.

    For example:
    rpm -ivh  vac.cmp-12.1.0.0-120323.ppc64.rpm --replacepkgs --replacefiles
    rpm -ivh  vacpp.cmp-12.1.0.0-120323.ppc64.rpm --replacepkgs --replacefiles

  3. Run new_install or vac_configure to re-configure the compiler.


Topic location: Before installing IBM XL C/C++ for Linux, V12.1 > The installation image and packages

Table 2. Utilization reporting tool package 1.1

Should read:

Table 2. Utilization reporting tool package 1.2

All references to the version of the utilization reporting tool (urt) in the Installation Guide should be changed to V1.2.


Compiler Reference
The following corrections and additions apply to the IBM XL C/C++ for Linux, V12.1 Compiler Reference:

Topic location: Tracking and reporting compiler usage > Understanding the utilization reporting tool

The tool is located in the /opt/ibmurt/1.1/bin directory.

Should read:

The tool is located in the /opt/ibmurt/1.2/bin directory.

A default configuration file ibmurt.cfg is provided in the /opt/ibmurt/1.1/config directory.

Should read:

A default configuration file ibmurt.cfg is provided in the /opt/ibmurt/1.2/config directory.

All references to the version of the utilization reporting tool (urt) in the Compiler Reference should be changed to V1.2.


Topic location: Compiler options reference > Individual option descriptions > -qalign

Defaults
-qalign=power
linuxppc

Should read:

Defaults
-qalign=linuxppc


Topic location: Compiler options reference > Individual option descriptions > -qdigraph

Purpose
Enables recognition of digraph key combinations or keywords to represent characters not found on some keyboards.

Should read:

Enables recognition of digraph key combinations C++ onlyand operator keywords C++ only to represent characters that are not found on some keyboards. Digraph key combinations include <:,   <%, and so on. C++ onlyOperator keywords include and, or, and so on. C++ only


Topic location: Compiler options reference > Individual option descriptions > -qinline

Note that the -qinline- and -qinline+ options are supported only by the XL C compiler.

Defaults
  • -qnoinline
  • At optimization levels of -O2 and higher, the default is -qinline=noauto
  • -qinline=auto:level=5 is the default suboption of -qinline

Parameters
noauto | auto
Enables or disables automatic inlining. If you do not specify any -qinline suboptions, -qinline=auto is the default.
Should read:

Defaults

If -qinline is not specified, the default option is -qnoinline at the -O0 or -qnoopt optimization level or -qinline=noauto:level=5:20 at the -O2 or higher optimization levels.

If -qinline is specified without any suboptions, the default option is -qinline=auto:level=5:20.

Parameters
noauto | auto
Enables or disables automatic inlining.

Topic location: Compiler options reference > Individual option descriptions > -O, -qoptimize

The following statement should be added under "Usage":

If optimization level -O3 or higher is specified on the command line, the -qhot and -qipa options that are set by the optimization level cannot be overridden by #pragma option_override(identifier, "opt(level, 0)") or #pragma option_override(identifier, "opt(level, 2)").


Topic location: Compiler options reference > Individual option descriptions > -qstaticlink

Syntax



Should read:



The following description should be added under Parameters:

xllibs

  • When you specify xllibs with nostaticlink, the compiler links the shared version of the XL compiler libraries.
  • When you specify xllibs with staticlink, the compiler links the static version of the XL compiler libraries.

For more information, see A new suboption xllibs added to -qstaticlink for XL C/C++ for Linux, V12.1 and XL Fortran for Linux, V14.1.


Topic location: Compiler options reference > Individual option descriptions > -qtune

The following rows in the Acceptable -qarch/-qtune combinations table:

-qarch option Default -qtune setting Available -qtune settings
pwr4 pwr4 auto | pwr4 | pwr5 | pwr7 | ppc970 | balanced
pwr5 pwr5 auto | pwr5 | pwr7 | balanced
pwr5x pwr5 auto | pwr5 | pwr7 | balanced

Should read:

-qarch option Default -qtune setting Available -qtune settings
pwr4 pwr4 auto | pwr4 | pwr5 | pwr6 | pwr7 | ppc970 | balanced
pwr5 pwr5 auto | pwr5 | pwr6 | pwr7 | balanced
pwr5x pwr5 auto | pwr5 | pwr6 | pwr7 | balanced


Topic location: Compiler pragmas reference > Individual pragma descriptions > #pragma option_override

Syntax



Should read:



Parameters

#pragma option_override value Equivalent compiler option
level, 0 -O
level, 2 -O2
level, 3 -O3
level, 4 -O4
level, 5 -O5
registerspillsize, size -qspill=size
size -qcompact
size, yes
size, no -qnocompact
strict, all -qstrict, -qstrict=all
strict, no, none -qnostrict
strict, suboption_list -qstrict=suboption_list

Should read:

#pragma option_override value Equivalent compiler option
level, 0 -O1
level, 2 -O21
level, 3 -O32
registerspillsize, size -qspill=size
size -qcompact
size, yes
size, no -qnocompact
strict  -qstrict, -qstrict=all
strict, yes
strict, no -qnostrict
strict, suboption_list -qstrict=suboption_list

Notes:
1. If optimization level -O3 or higher is specified on the command line,  #pragma option_override( identifier , "opt(level, 0)") or  #pragma option_override( identifier , "opt(level, 2)") does not turn off the implication of the -qhot and -qipa options.
2. Specifying -O3 implies -qhot=level=0. However, specifying  #pragma option_override( identifier , "opt(level, 3)") in source code does not imply -qhot=level=0.


Topic location: Compiler pragmas reference > Individual pragma descriptions > #pragma reg_killed_by

fs
    Floating-point and status control register

Should read:

fsr
    Floating-point and status control register


Topic location: Compiler pragmas reference > Individual pragma descriptions > #pragma ibm independent_loop

This section should be moved out of the " Pragma directives for parallel processing" section and be put under the " Individual pragma descriptions" section directly.

The following statement should be added:

This pragma only takes effect if you specify the -qsmp or -qhot compiler option.


Topic location: Compiler built-in functions > Synchronization and atomic built-in functions > Synchronization functions > __lwsync, __iospace_lwsync

Load Word Synchronize

Should read:

Lightweight Synchronize


Topic location: Compiler built-in functions > GCC atomic memory access built-in functions

The data types of the parameters that are supported in these functions include Boolean type and any integral scalar type of 1, 2, 4 or 8 bytes, listed as follows.

Should read:

In the prototype of each function, the parameter types T, U, and V can be of pointer or integral type. U and V can also be of real floating-point type, but only when T is of integral type. The following tables list the integral and floating-point types that are supported by these built-in functions.

Table 1. Supported data types

Should read:

Table 1. Supported integral data types

The following data types in Table 1. Supported integral data types

C++ only bool C++ onlywchar_t
C only _Bool

Should read:

C++ only bool C only _Bool

The following table should be added:

Table 2. Supported floating-point data types
float
double
long double

Language Reference
The following corrections and additions apply to the IBM XL C/C++ for Linux, V12.1 Language Reference:

Topic location: Declarators > Pointers > Type-based aliasing

In the example:



Should read:



The compiler determines that the result of f += 1.0; is never used subsequently. Thus, the optimizer may discard the statement from the generated code.

Should read:

The compiler determines that the result of f += 1.0 does not affect the value of *p. Thus, the optimizer might move the assignment after the printf statement.

Topic location: Declarators > Initializers > Initialization of structures and unions

You do not have to initialize all members of a structure or union; the initial value of uninitialized structure members depends on the storage class associated with the structure or union variable. In a structure declared as static, any members that are not initialized are implicitly initialized to zero of the appropriate type; the members of a structure with automatic storage have no default initialization. The default initializer for a union with static storage is the default for the first component; a union with automatic storage has no default initialization.

The following definition shows a partially initialized structure:


struct address {
                int street_no;
                char *street_name;
                char *city;
                char *prov;
                char *postal_code;
              };
struct address temp_address =
              { 44, "Knyvet Ave.", "Hamilton", "Ontario" };


The values of temp_address are:

Member
Value
temp_address.street_no 44
temp_address.street_name address of string "Knyvet Ave."
temp_address.city address of string "Hamilton"
temp_address.prov address of string "Ontario"
temp_address.postal_code Depends on the storage class of the temp_address variable; if it is static, the value would be NULL.

Should read:

You do not have to initialize all members of structure variables. If a structure variable does not have an initializer, the initial values of the structure members depend on the storage class associated with the structure variable:
  • If a structure variable has static storage, its members are implicitly initialized to zero of the appropriate type.
  • If a structure variable has automatic storage, its members have no default initialization.

If a structure variable is partially initialized, all the uninitialized structure members are implicitly initialized to zero no matter what the storage class of the structure variable is. See the following example:

struct one {
   int a;
   int b;
   int c;
};
void main(){
   struct one z1;               // Members in z1 do not have default initial values.
   static struct one z2;        // z2.a=0, z2.b=0, and z2.c=0.
   struct one z3 = {1};         // z3.a=1, z3.b=0, and z3.c=0.
}


In this example, structure variable z1 has automatic storage, and it does not have an initializer, so all the members in z1 do not have default initial values. Structure variable z2 has static storage, and all its members are implicitly initialized to zero. Structure variable z3 is partially initialized, so all its uninitialized members are implicitly initialized to zero.

You do not have to initialize all members of a union. The default initializer for a union with static storage is the default for the first component. A union with automatic storage has no default initialization.

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Document information


More support for:

XL C/C++ for Linux
Documentation

Software version:

12.1

Operating system(s):

Linux

Reference #:

1588552

Modified date:

2014-09-30

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