User's Guide

Preprocessor Options

The following options are accepted by the preprocessor:

-C

Using the -C option prevents the preprocessor from stripping comments. See the description of

cpp in the cpp(1) manpage for details.

-dM

When -dM is present, instead of normal preprocessor output the compiler lists the #define

directives it encounters as it preprocesses the file, thus providing a list of all macros that are in

effect at the start of the compilation. The -dM option requires that -P or -E also be specified.

A common use of this option is to determine the compiler's predefined macros. For example:

touch foo.c ; cc -E -dM foo.c

-Dname

-Dname[=def]

name is the symbol name that is defined for the preprocessor.

def is the definition of the symbol name (name).

The -Dname option defines a symbol name (name) to the preprocessor, as if defined by the

preprocessing directive#define.

If no definition (def) is given, the name is defined as 1.

NOTE: __ia64 and __HP_aCC are defined automatically.

Example:

The following example defines the preprocessor symbol DEBUGFLAG and gives it the value 1.

aCC -DDEBUGFLAG file.C

The following program uses this symbol:

#include <iostream.h>

int main(){

int i, j;

#ifdef DEBUGFLAG

int call_count=0;

#endif

/* ... */

}

-E

Using the -E option runs only the preprocessor on the named C++ files and sends the result to

standard output (stdout).

An exception to this rule is when-E is used with +Make[d] option, the only output is the make

dependency information. Unlike the -P option, the output of -E contains #line entries indicating

the original file and line numbers.

Redirecting Output From This Option

Use the -.suffix option to redirect the output of this option.

72 Command-Line Options