Supported Pragma Directives |
The Wave preprocessor library supports a couple of specific #pragma directives, which may be used to control some of the library features. All directives described here are usable as conventional #pragma directives and as operator _Pragma (if variadics are enabled). So for instance the following directives are functionally identical:
#pragma wave trace(enable)
and
_Pragma("wave trace(enable)")
All Wave specific pragma's must have the general form 'wave option[(value)]', where 'wave' is the specific keyword, 'option' is the concrete pragma functionality to trigger and 'value' is an optional value to be supplied to the 'option' functionality. The following table lists all possible pragma functions supported by the Wave library.
Supported pragma's |
|||
pragma option |
pragma value |
description |
supported by |
trace |
enable/on/1 |
Enable or disable the tracing of the macro expansion process. This is needed, even if there is given the --trace command line option, because the trace output is generated only, if there is at least one trace(enable) pragma found. |
Wave library |
stop |
message |
Stop the execution of Wave and print out the given message. This is very helpful for direct debugging purposes. |
Wave library |
system |
command |
Try to spawn the 'command' as a new operating system
command and intercept the generated stdout and stderr. The stdout output
of this command (if any) is retokenized and used as the replacement text
for the whole pragma, the stderr output is ignored. The command is considered
to be successful, if/when the return value is zero, otherwise an error
is reported. |
Wave library |
timer |
restart/0 |
The value restart set the current elapsed
time to 0 and restarts the timer. |
Wave driver |
All pragma's not listed here but flagged as 'wave' are reported as
errors. The handling of all remaining pragma's depends on the compilation constant
WAVE_RETURN_PRAGMA_DIRECTIVES
, which allows to specify,
if those pragmas are left unchanged in the output stream or not. Please note,
that the operator _Pragma variant is always subject to full preprocessing, before
the pragma itself is evaluated. The #pragma variant is subject to preprocessing
only, if the WAVE_PREPROCESS_PRAGMA_BODY
compilation constant
was specified during compilation.For more information about the possible compilation
constants look here.
Additionally the Wave preprocessor supports the #pragma once directive, which specifies that the file, in which the pragma resides, will be included (opened) only once by the compiler in a build. This may be used to optimize the preprocessing of larger compilation units, which include a lot of files.
Copyright © 2003-2004 Hartmut Kaiser
Use, modification and distribution is subject to the Boost Software
License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)