This page lists all IBM C and C++ Compilers options, specifying each compiler option's type and if it exists, default value. Where a * appears beside the default value for a compiler option, see the description for that option for special notes regarding the default value.
To get detailed information on any option listed, click on the that option's name in the table.
| Option Name | Type | Default | Description |
-flag |
- |
Compiles any file, filename.nnn, as a C++ language file, where nnn is any suffix other than .o, .a, or .s. | |
-flag |
- |
Traces the compilation without doing anything. | |
-qopt |
- |
Selects 32- or 64-bit compiler mode. | |
| Option Name | Type | Default | Description |
-qopt |
See alias. |
Specifies which type-based aliasing is to be used during optimization. | |
-qopt |
align=full |
Specifies what aggregate alignment rules the compiler uses for file compilation. | |
-qopt |
ansialias* |
Specifies whether type-based aliasing is to be used during optimization. | |
-qopt |
arch=com |
Specifies the architecture on which the executable program will be run. | |
-qopt |
noassert |
Requests the compiler to apply aliasing assertions to your compilation unit. | |
-qopt |
noattr |
Produces a compiler listing that includes an attribute listing for all identifiers. | |
| Option Name | Type | Default | Description |
-flag |
- |
Determines substitute path names for the compiler, assembler, linkage editor, and preprocessor. | |
-flag |
unsigned |
Specifies if bitfields are signed. | |
-flag |
- |
Tells the linkage editor to accept both .so and .a library file types. | |
-flag |
bdynamic |
Determines which types of library files are searched by the linkage editor. | |
| Option Name | Type | Default | Description |
-flag |
- |
Preserves comments in preprocessed output. | |
-flag |
- |
Instructs the compiler to pass source files to the compiler only. | |
-qopt |
chars=unsigned |
Instructs the compiler to treat all variables of type char as either signed or unsigned. | |
-qopt |
nocheck |
Generates code which performs certain types of run-time checking. | |
-qopt |
nocompact |
When used with optimization, reduces code size where possible, at the expense of execution speed. | |
-qopt |
nocpluscmt |
Use this option if you want C++ comments to be recognized in C source files. | |
| Option Name | Type | Default | Description |
-flag |
- |
Defines the identifier name as in a #define preprocessor directive. | |
-qopt |
dataimported |
Mark data as local or imported. | |
-qopt |
nodbxextra |
Specifies that all typedef declarations, struct, union, and enum type definitions are included for xldb processing. | |
-qopt |
nodigraph |
Allows use of digraph character sequences in your program. | |
-qopt |
nodollar |
Allows the $ symbol to be used in the names of identifiers. | |
| Option Name | Type | Default | Description |
-flag |
- |
Runs the source files named in the compiler invocation through the preprocessor. | |
-qopt |
enum=int |
Specifies the amount of storage occupied by the enumerations. | |
-qopt |
noextchk |
Generates bind-time type checking information and checks for compile-time consistency. | |
| Option Name | Type | Default | Description |
-flag |
- |
Names an alternative configuration file for xlC. | |
-qopt |
nofdpr |
Collect program information for use with the AIX fdpr performance-tuning utility. | |
-qopt |
flag=i:i |
Specifies the minimum severity level of diagnostic messages to be reported. | |
-qopt |
See float. |
Specifies various floating point options to speed up or improve the accuracy of floating point operations. | |
-qopt |
noflttrap |
Generates extra instructions to detect and trap floating point exceptions. | |
-qopt |
fold |
Specifies that constant floating point expressions are to be evaluated at compile time. | |
-qopt |
nofullpath |
Specifies what path information is stored for files when you use -g and the graphical debugger, xldb. | |
| Option Name | Type | Default | Description |
-flag |
- |
Linkage editor (ld command) option only. Used to generate a dynamic libary file. | |
-flag |
- |
Generates debugging information used by the xldb graphical debugger. | |
-qopt |
nogenpcomp |
Generates a precompiled version of any header file for which the original source is used. | |
-qopt |
nogenproto |
Produces ANSI prototypes from K&R function definitions. | |
| Option Name | Type | Default | Description |
-qopt |
halt=s |
Instructs the compiler to stop after the compilation phase when it encounters errors of specified severity or greater. | |
-qopt |
noheapdebug |
Enables debug versions of memory management functions. | |
-qopt |
nohsflt |
Speeds up calculations by removing range checking on single-precision float results and on conversions from floating point to integer. | |
-qopt |
nohssngl |
Specifies that single-precision expressions are rounded only when the results are stored into float memory locations. | |
| Option Name | Type | Default | Description |
-flag |
- |
Specifies an additional search path if the file name in the #include directive is not specified using its absolute path name. | |
-qopt |
noidirfirst |
Specifies the search order for files included with the #include "file_name" directive. | |
-qopt |
noignerrno |
Allows the compiler to perform optimizations that assume errno is not modified by system calls. | |
-qopt |
- |
This option is useful for detecting aliasing pragma errors. | |
-qopt |
noinfo |
Produces informational messages. | |
-qopt |
noinitauto |
Initializes automatic storage to the two-digit hexadecimal byte value hex_value. | |
-qopt |
noinlglue |
Generates fast external linkage by inlining the pointer glue code necessary to make a call to an external function or a call through a function pointer. | |
-qopt |
See inline. |
Attempts to inline functions instead of generating calls to a function. | |
-qopt |
object (compile-time), |
Turns on or customizes a class of optimizations known as interprocedural analysis (IPA). | |
-qopt |
- |
Specifies functions in the source file that have no side effects. | |
| Option Name | Type | Default | Description |
-flag |
See L. |
Searches the specified directory for library files specified by the -l option. | |
-flag |
See l. |
Searches a specified library for linking. | |
-qopt |
langlvl=ansi* |
Selects the C or C++ language level for compilation. | |
-qopt |
noldbl128 |
Increases the size of long double type from 64 bits to 128 bits. | |
-qopt |
nolibansi |
Assumes that all functions with the name of an ANSI C library function are in fact the system functions. | |
| linedebug | -qopt | nolinedebug | Generates abbreviated line number and source file name information for the debugger. |
-qopt |
nolist |
Produces a compiler listing that includes an object listing. | |
-qopt |
nolistopt |
Produces a compiler listing that displays all options in effect. | |
-qopt |
longlong* |
Allows long long types in your program. | |
| Option Name | Type | Default | Description |
-flag |
- |
Creates an output file that contains targets suitable for inclusion in a description file for the AIX make command. | |
-flag |
- |
Substitutes inline code for calls to function alloca as if #pragma alloca directives are in the source code. | |
-qopt |
nomacpstr |
Converts Pascal string literals into null-terminated strings where the first byte contains the length of the string. | |
-qopt |
maf |
Specifies whether the floating-point multiply-add instructions are to be generated. | |
-qopt |
- |
Creates an output file that contains targets suitable for inclusion in a description file for the AIX make command. | |
-qopt |
nomaxerr |
Instructs the compiler to halt compilation when a specified number of errors of specified or greater severity is reached. | |
-qopt |
maxmem=2048 |
Limits the amount of memory used for local tables of specific, memory-intensive optimizations. | |
-qopt |
nombcs |
Use the -qmbcs option if your program contains multibyte characters. | |
| Option Name | Type | Default | Description |
-qopt |
- |
Suppresses listings. | |
| Option Name | Type | Default | Description |
-qopt, -flag |
nooptimize |
Optimizes code at a choice of levels during compilation. | |
-flag |
- |
Specifies a name or directory for the output executable file(s) created either by the compiler or the linkage editor. | |
-qopt |
noonce |
Avoids including a header file more than once even if it is specified in several of the files you are compiling. | |
| Option Name | Type | Default | Description |
-flag |
- |
Preprocesses the C or C++ source files named in the compiler invocation and creates an output preprocessed source file for each input source file. | |
-flag |
- |
Sets up the object files produced by the compiler for profiling. | |
-qopt |
nopascal |
Ignores the word pascal in type specifiers and function declarations. | |
-qopt |
nopdf1 |
Tunes optimizations through Profile-Directed Feedback. | |
-flag |
- |
Sets up the object files for profiling, but provides more information than is provided by the -p option. | |
-qopt |
nophsinfo |
Reports the time taken in each compilation phase. | |
-qopt |
- |
Specifies the priority level for the initialization of static constructors | |
-qopt |
proclocal* |
Mark functions as local, imported, or unknown. | |
-qopt |
noproto |
Assumes all functions are prototyped. | |
| Option Name | Type | Default | Description |
-flag |
See Q. |
Attempts to inline functions instead of generating calls to a function. | |
| Option Name | Type | Default | Description |
-flag |
- |
Produces a relocatable object. | |
-qopt |
norndsngl |
Specifies that the result of each single-precision (float) operation is to be rounded to single precision. | |
-qopt |
ro* |
Specifies the storage type for string literals. | |
-qopt |
roconst* |
Specifies the storage location for constant values. | |
-qopt |
norrm |
Prevents floating-point optimizations that are incompatible with run-time rounding to plus and minus infinity modes. | |
-qopt |
nortti |
Generates run-time type identification (RTTI) information for the typeid operator and the dynamic_cast operator. | |
-qopt |
norwvftable |
Specifies whether virtual function tables are to be put into read/write or read-only storage. | |
| Option Name | Type | Default | Description |
-flag |
- |
Generates an assembly language file (.s) for each source file. | |
-qopt |
noshowinc |
If used with -qsource, all the include files are included in the source listing. | |
-qopt |
nosource |
Produces a compiler listing and includes source code. | |
-qopt |
spill=512 |
Specifies the size of the register allocation spill area. | |
-qopt |
nospnans |
Generates extra instructions to detect signalling NaN on conversion from single precision to double precision. | |
-qopt |
nosrcmsg |
Adds the corresponding source code lines to the diagnostic messages in the stderr file. | |
-qopt |
nostatsym |
Adds user-defined, non-external names that have a persistent storage class to the name list. | |
-qopt |
stdinc |
Specifies which files are included with #include <file_name> and #include "file_name" directives. | |
-qopt |
See strict. |
Turns off aggressive optimizations that have the potential to alter the semantics of your program. | |
-qopt |
See strict_induction. |
Disables loop induction variable optimizations that have the potential to alter the semantics of your program. | |
-qopt |
- |
Causes the compiler to perform syntax checking without generating an object file.. | |
| Option Name | Type | Default | Description |
-flag |
See t. |
Adds the prefix specified by the -B option to designated programs. | |
-qopt |
tabsize=8 |
Changes the length of tabs as perceived by the compiler. | |
-qopt |
full* |
Sets traceback table characteristics. | |
-qopt |
See tempinc. |
Generates separate include files for template functions and class declarations, and places these files in a directory which can be optionally specified. | |
-qopt |
tempmax=1 |
Specifies the maximum number of template include files to be generated by the tempinc option for each header file. | |
-qopt |
See tune. |
Specifies the architecture for which the executable program is optimized. | |
-qopt |
notwolink* |
Minimizes the number of static constructors included from libraries. | |
| Option Name | Type | Default | Description |
-flag |
- |
Undefines a specified identifier defined by the compiler or by the -D option. | |
-qopt |
nounique |
Generates unique names for static constructor/deconstructor file compilation units. | |
-qopt |
unroll=4* |
Unrolls inner loops in the program by a specified factor. | |
-qopt |
noupconv* |
Preserves the unsigned specification when performing integral promotions. | |
-qopt |
nousepcomp |
Use precompiled header files for any files that have not changed since the precompiled header was created. | |
| Option Name | Type | Default | Description |
-flag |
- |
Instructs the compiler to report information on the progress of the compilation. | |
-flag |
See vftable. |
Controls the generation of virtual function tables. | |
| Option Name | Type | Default | Description |
-flag |
- |
Passes the listed words to a designated compiler program. | |
-flag |
- |
Requests that warning messages be suppressed. | |
-qopt |
nowarn64 |
Enables warning of possible long to integer data truncations. | |
| Option Name | Type | Default | Description |
-qopt |
noxcall |
Generates code to static routines within a compilation unit as if they were external calls. | |
-qopt |
noxref |
Produces a compiler listing that includes a cross-reference listing of all identifiers. |
|
| Option Name | Type | Default | Description |
-flag |
- |
Specifies the compile-time rounding mode of constant floating-point expressions. |
Options that Specify Compiler Characteristics
Options that Specify Debugging Features
Options that Specify Preprocessor Options
Options that Specify Compiler Output
Options that Define the Compiler Object Code Produced
Options that Specify Linkage Options
Resolving Conflicting Compiler Options
