-WH
: Send additional arguments to the C preprocessor
When the -H
option (see -H_) is used, the C preprocessor is
invoked to scan include header files for typedef's and class
declarations. That is called with a standard set of options.
(Presently, gcc
is actually called to invoke the preprocessor; it
is sent the options -E
, -P
, and -I
.) Occasionally
it may be necessary to send additional options. Those can be specified
as the (string) argument to -WH
. Thus, to define two macros to the
preprocessor, one could say either of
-WH-Dtest1=1 -WH-Dtest2=2 -WH"-Dtest1=1 -Dtest2=2"
The first form shows that -WH
accretes to earlier uses. The
second form shows how to handle embedded blanks (in a UNIX shell).
Then, if one were programming in C, use of -H
would issue the
system command
gcc -E -P -Dtest1=1 -Dtest2=2