z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

c89, cc, and c++
You can specify an MVS data set name as an include file search directory.
Also, MVS data set names can explicitly be specified on #include
directives. You can indicate both by specifying a leading double slash (//).
Example: To include the include file DEF that is a member of the MVS PDS
ABC.HDRS, code your C or C++ source as follows:
#include
MVS data set include files are handled according to z/OS XL C/C++
compiler conversion rules (see Usage Note 4 on page 98). When specifying
an #include directive with a leading double slash (in a format other than
#include and #include), the specified name
is paired only with MVS data set names specified on the -I option. That is,
when you explicitly specify an MVS data set name, any z/OS UNIX file
system directory names specified on the -I option are ignored.
-L directory
Specifies the directories to be used to search for archive libraries specified
by the -l operand. The directories are searched in the order specified,
followed by the usual places. You cannot specify an MVS data set as an
archive library directory.
For information on specifying C370LIB libraries, see the description of the -l
libname operand. Also see Usage Note 7 on page 99 for a description of
the usual places.
-0, -O (-1), -2, -3
Specifies the level of compiler optimization (including inlining) to be used.
The level -1 (number one) is equivalent to -O (capital letter O). The level -3
gives the highest level of optimization. The default is -0 (level zero), no
optimization and no inlining, when not using IPA (Interprocedural Analysis).
When optimization is specified, the default is ANSIALIAS. The ANSIALIAS
default specifies whether type-based aliasing is to be used during
optimization. That is, the optimizer assumes that pointers can only be used
to access objects of the same type. Type-based aliasing improves
optimization. Applications that use pointers that point to objects of a
different type will need to specify NOANSIALIAS when the optimization
compiler option is specified. If your application works when compiled with
no optimization and fails when compiled with optimization, then try
compiling your application with both optimization and NOANSIALIAS
compiler options. The z/OS XL C/C++ User’s Guide contains more
information on ANSIALIAS.
Notes:
1. Options can also be specified as -O1 (using capital letter O), -O2, and
-O3. For further information, see Usage Note 12 on page 100.
2. These options cannot be overridden by specifying optimization options
using the -Wc syntax. This behavior differs from the behavior of the xlc
utility, which allows the use of -q and -Wc syntax to override the flag
optimization options.
Example: The following is an example of a compile with the highest level of
optimization and no type-based aliasing:
c89 -o outfile -O3 -Wc,NOANSIALIAS file.c
74 z/OS V1R9.0 UNIX System Services Command Reference
When optimization is specified, you may want to obtain a report on the
amount of inlining performed and increase or decrease the level of inlining.