| The Context Policy | |
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Introduction
Header 'wave/preprocessing_hooks.hpp' synopsis
Member functions
Please note that the following description relates to the new preprocessing hooks interface used by default starting with the Boost V1.35.0 release. If you are interested in the older interface please look here.
The context policy is used to provide callback hooks, which are called from inside the library into the user code, whenever
This policy type is used as a template parameter to the boost::wave::context<> object, where the default policy provides empty hook functions only.
namespace boost {
namespace wave {
namespace context_policies {
struct default_preprocessing_hooks {
// general hook functions template <typename ContextT, typename TokenT>
bool found_directive(ContextT const &ctx,
TokenT const &directive);
template <typename ContextT, typename ExceptionT>
void throw_exception(ContextT const &ctx,
ExceptionT const& e);
// test, whether a given token may be skipped
template <typename ContextT>
bool may_skip_whitespace (ContextT const& ctx,
TokenT &token, bool &skipped_newline);
// Conditional compilation template <
typename ContextT, typename TokenT,
typename ContainerT
>
bool evaluated_conditional_expression(
ContextT const &ctx, TokenT const& directive,
ContainerT const& expression, bool expression_value);
template <typename ContextT, typename TokenT>
void skipped_token(ContextT const &ctx,
TokenT const& token);
template <typename ContextT, typename TokenT>
TokenT const& generated_token(ContextT const &ctx,
TokenT const& token);
// macro expansion tracing template < typename ContextT, typename TokenT, typename ContainerT,
typename IteratorT
>
bool expanding_function_like_macro(
ContextT const &ctx, TokenT const ¯odef,
std::vector<TokenT> const &formal_args,
ContainerT const &definition, TokenT const ¯ocall,
std::vector<ContainerT> const &arguments,
IteratorT const &seqstart, Iterator const &seqend);
template <typename ContextT, typename TokenT, typename ContainerT>
bool expanding_object_like_macro(
ContextT const &ctx, TokenT const ¯o,
ContainerT const &definition, TokenT const ¯ocall);
template <typename ContextT, typename ContainerT>
void expanded_macro(ContextT const &ctx,
ContainerT const &result);
template <typename ContextT, typename ContainerT>
void rescanned_macro(ContextT const &ctx,
ContainerT const &result);
// include file tracing functions template <typename ContextT>
bool found_include_directive(ContextT const &ctx,
std::string const &filename, bool include_next);
template <typename ContextT>
void opened_include_file(ContextT const &ctx,
std::string const &relname, std::string const& absname,
bool is_system_include);
template <typename ContextT>
void returning_from_include_file(ContextT const &ctx);
template <typename ContextT>
void detected_include_guard(ContextT const &ctx, std::string const& filename, std::string const& include_guard);
template <typename ContextT, typename TokenT>
void detected_pragma_once(ContextT const &ctx, TokenT const& pragma_token, std::string const& filename);
// interpretation of #pragma's of the form // 'wave option[(value)]' template <typename ContextT, typename ContainerT>
bool interpret_pragma(ContextT const &ctx, ContainerT &pending,
typename ContextT::token_type const &option,
ContainerT const &values,
typename ContextT::token_type const &pragma_token);
// macro definition hooks template <
typename ContextT, typename TokenT, typename ParametersT, typename DefinitionT
>
void defined_macro(ContextT const &ctx, TokenT const &name, bool is_functionlike, ParametersT const ¶meters,
DefinitionT const &definition, bool is_predefined);
template <typename ContextT, typename TokenT>
void undefined_macro(ContextT const &ctx,
TokenT const &name);
// #error and #warning directive hooks template <typename ContextT, typename ContainerT>
bool found_warning_directive(ContextT const &ctx,
ContainerT const &message);
template <typename ContextT, typename ContainerT>
bool found_error_directive(ContextT const &ctx,
ContainerT const &message);
// #line directive hook template <typename ContextT, typename ContainerT>
void found_line_directive(ContextT const &ctx,
ContainerT const &arguments, unsigned int line,
std::string const& filename);
};
}}} // namespace boost::wave::context_policies
template <typename ContextT, typename TokenT>
bool found_directive(ContextT const& ctx, TokenT const &directive);
The function found_directive is called, whenever the preprocessor has detected one of the preprocessing directives (#define, #undef, #if, #idef, #ifndef, #elif, #endif, #error, #include, #pragma or #warning) .
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter directive refers to the token containing the detected preprocessing directive.
If the return value is true, the directive will be skipped altogether, i.e. no preprocessing is done. The overall directive is replaced by a single newline character. If the return value is false, the directive is processed in the normal manner.
template <typename ContextT, typename ExceptionT>
void throw_exception(ContextT const &ctx,
ExceptionT const& e);
he function throw_exception is called, whenever a preprocessing exception occurs .
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The parameter e is the exception object containing detailed error information.
template <typename ContextT, typename TokenT>
bool may_skip_whitespace(ContextT const& ctx, TokenT &token,
bool& skipped_newline);
The function may_skipwhitespace will be called by the library, whenever a token is about to be returned to the calling application.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Wave V1.2.4 release.
The token parameter holds a reference to the current token. The policy is free to change this token if needed.
The skipped_newline parameter holds a reference to a boolean value which should be set to true by the policy function whenever a newline is going to be skipped.
If the return value is true, the given token is skipped and the preprocessing continues to the next token. If the return value is false, the given token is returned to the calling application. Caution has to be used, because by returning true the policy function is able to force skipping even significant tokens not only whitespace.
evaluated_conditional_expression
template <typename ContextT, typename TokenT, typename ContainerT> bool evaluated_conditional_expression(ContextT const& ctx,
TokenT const& directive, ContainerT const& expression,
bool expression_value);
The function evaluated_conditional_expression is called, whenever the preprocessor has encountered a #if, #elif, #ifdef or #ifndef directive. This hook gets passed the non-expanded conditional expression (as it was given in the analysed source file) and the result of the evaluation of this expression in the current preprocessing context.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The token parameter holds a reference to the evaluated directive token.
The parameter expression holds the non-expanded token sequence comprising the evaluated expression.
The parameter expression_value contains the result of the evaluation of the expression in the current preprocessing context.
The return value defines, whether the given expression has to be evaluated again, allowing to decide which of the conditional branches should be expanded. You need to return 'true' from this hook function to force the expression to be re-evaluated. Note, this was changed from a 'void' for the Boost V1.35.0 release.
template <typename ContextT, typename TokenT>
void skipped_token(ContextT const& ctx, TokenT const& token);
The function skipped_token is called, whenever a token is about to be skipped due to a false preprocessor condition (code fragments to be skipped inside the not evaluated conditional #if/#else/#endif branches).
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter token refers to the token to be skipped.
template <typename ContextT, typename TokenT>
TokenT const& generated_token(ContextT const& ctx, TokenT const& token);
The function generated_token is called, whenever a token is about to be returned from the library.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter token refers to the token about to be returned from the library. This function may alter the token, but in this case it must be implemented with a non-const reference for the token parameter, allowing to modify the token in place.
The default behavior is to return the passed token reference unchanged to the caller.
template <typename ContextT, typename TokenT, typename ContainerT>
bool expanding_function_like_macro(
ContextT const& ctx, TokenT const ¯odef,
std::vector<TokenT> const &formal_args,
ContainerT const &definition, TokenT const ¯ocall,
std::vector<ContainerT> const &arguments,
IteratorT const &seqstart, Iterator const &seqend);
The function expanding_function_like_macro is called, whenever a function-like macro is to be expanded, i.e. before the actual expansion starts.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The macroname parameter marks the position where the macro to expand is defined. It contains the token which identifies the macro name used inside the corresponding macro definition.
The formal_args parameter holds the formal arguments used during the definition of the macro.
The definition parameter holds the macro definition for the macro to trace. This is a standard STL container which holds the token sequence identified during the macro definition as the macro replacement list.
The macrocall parameter marks the position where this macro is invoked. It contains the token, which identifies the macro call inside the preprocessed input stream.
The arguments parameter holds the macro arguments used during the invocation of the macro. This is a vector of standard STL containers which contain the token sequences identified at the position of the macro call as the arguments to be used during the macro expansion.
The parameters seqstart and seqend point into the input token stream allowing to access the whole token sequence comprising the macro invocation (starting with the opening parenthesis and ending after the closing one).
If the return value is true, the macro is not expanded, i.e. the overall macro invocation sequence, including the parameters are copied to the output without further processing . If the return value is false, the macro is expanded as expected.
template <typename ContextT, typename TokenT, typename ContainerT>
bool expanding_object_like_macro(
ContextT const& ctx, TokenT const ¯o,
ContainerT const &definition, TokenT const ¯ocall);
The function expanding_object_like_macro is called, whenever a object-like macro is to be expanded, i.e. before the actual expansion starts.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The macroname parameter marks the position where the macro to expand is defined. It contains the token which identifies the macro name used inside the corresponding macro definition.
The definition parameter holds the macro definition for the macro to trace. This is a standard STL container which holds the token sequence identified during the macro definition as the macro replacement list.
The macrocall parameter marks the position where this macro is invoked. It contains the token which identifies the macro call inside the preprocessed input stream.
If the return value is true, the macro is not expanded, i.e. the macro symbol is copied to the output without further processing. If the return value is false, the macro is expanded as expected.
template <typename ContextT, typename ContainerT>
void expanded_macro(ContextT const& ctx, ContainerT const &result);
The function expanded_macro is called whenever the expansion of a macro is finished, the replacement list is completely scanned and the identified macros herein are replaced by its corresponding expansion results, but before the rescanning process starts.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter result contains the the result of the macro expansion so far. This is a standard STL container containing the generated token sequence.
template <typename ContextT, typename ContainerT>
void rescanned_macro(ContextT const& ctx, ContainerT const &result);
The function rescanned_macro is called whenever the rescanning of a macro is finished, i.e. the macro expansion is complete.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter result contains the the result of the whole macro expansion. This is a standard STL container containing the generated token sequence.
template <typename ContextT>
bool found_include_directive(ContextT const& ctx,
std::string const &filename, bool include_next);
The function found_include_directive is called whenever whenever a #include directive was located..
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter filename contains the (expanded) file name found after the #include directive. This has the format <file>, "file" or file. The formats <file> or "file" are used for #include directives found in the preprocessed token stream, the format file is used for files specified through the --force_include command line argument.
The parameter include_next is set to true if the found directive was a #include_next directive and the BOOST_WAVE_SUPPORT_INCLUDE_NEXT preprocessing constant was defined to something != 0.
If the return value is true, the include directive is not executed, i.e. the file to include is not loaded nor processed. The overall directive is replaced by a single newline character. If the return value is false, the directive is executed in a normal manner.
template <typename ContextT>
void opened_include_file(ContextT const& ctx,
std::string const &rel_filename, std::string const &abs_filename,
bool is_system_include);
The function opened_include_file is called whenever a file referred by an #include directive was successfully located and opened.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter rel_filename contains the (normalised) probably relative file system path of the opened file. The concrete format of this file name depends on the format of the include search path given to the library beforehand.
The parameter abs_filename contains the (normalised) full file system path of the opened file.
The is_system_include parameter denotes, if the given file was found as a result of a #include <...> directive.
template <typename ContextT>
void returning_from_include_file(ContextT const& ctx);
The function returning_from_include_file is called whenever an included file is about to be closed after it's processing is complete.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
template <typename ContextT>
void detected_include_guard(ContextT const& ctx, std::string const& filename, std::string const& include_guard);
The function detected_include_guard is called whenever an include file is about to be added to the list of #pragma once headers as the result of a detected include guard scheme. That means this header file will not be opened and parsed again even if it is specified in a later #include directive.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The parameter filename contains the file system path of the opened file (this is relative to the directory of the currently processed file or a absolute path depending on the paths given as the include search paths).
The parameter include_guard contains the name of the detected include guard.
template <typename ContextT, typename TokenT>
void detected_pragma_once(ContextT const& ctx, TokenT const& pragma_token, std::string const& filename);
The function detected_pragma_once is called whenever either an include file is about to be added to the list of #pragma once headers as the result of a detected #pragma once directive. That means this header file will not be opened and parsed again even if it is specified in a later #include directive.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The parameter pragma_token refers to the token "#pragma" triggering this preprocessing hook.
The parameter filename contains the file system path of the opened file (this is relative to the directory of the currently processed file or a absolute path depending on the paths given as the include search paths).
template <typename ContextT, typename ContextT, typename ContainerT>
bool interpret_pragma(ContextT const &ctx, ContainerT &pending,
typename ContextT::token_type const &option,
ContainerT const &values,
typename ContextT::token_type const &pragma_token);
The function interpret_pragma is called whenever an unrecognized #pragma wave ... or operator _Pragma("wave ...") is found in the input stream.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The pending parameter may be used to push tokens back into the input stream which are to be used as the replacement text for the whole #pragma wave() directive. If this sequence is left empty, no replacement takes place, i.e. the interpreted directive is removed from the generated token stream.
The option parameter contains the name of the interpreted pragma.
The values parameter holds the value of the parameter provided to the pragma operator.
The pragma_token parameter contains the actual #pragma token which may be used for extraction of the location information for some error output.
If the return value is 'false', the whole #pragma directive is interpreted as unknown and a corresponding error message is issued. A return value of 'true' signs a successful interpretation of the given #pragma.
template <
typename ContextT, typename TokenT, typename ParametersT, typename DefinitionT
>
void defined_macro(ContextT const& ctx,
TokenT const &name, bool is_functionlike,
ParametersT const ¶meters, DefinitionT const &definition,
bool is_predefined);
The function defined_macro is called whenever a macro was defined successfully.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter name is a reference to the token holding the macro name.
The parameter is_functionlike is set to true whenever the newly defined macro is defined as a function like macro.
The parameter parameters holds the parameter tokens for the macro definition. If the macro has no parameters or if it is a object like macro, then this container is empty.
The parameter definition contains the token sequence given as the replacement sequence (definition part) of the newly defined macro.
The parameter is_predefined is set to true for all macros predefined during the initialisation pahase of the library.
template <typename ContextT, typename TokenT>
void undefined_macro(ContextT const& ctx, TokenT const &name);
The function undefined_macro is called whenever a macro definition was removed successfully.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user. Note, this parameter was added for the Boost V1.35.0 release.
The parameter name holds the token of the macro which definition was removed.
template <typename ContextT, typename ContainerT>
bool found_warning_directive(ContextT const& ctx,
ContainerT const &message);
The function found_warning_directive is called whenever a #warning directive has been encountered. Note, this function was added for the Boost V1.35.0 release. This function will be called only if the BOOST_WAVE_SUPPORT_WARNING_DIRECTIVE compile time constant was defined to something not equal to zero (see the Compile Time Configuration for more information).
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The parameter message references the argument token sequence of the encountered #warning directive.
If the return value is false, the library throws a preprocessor exception of the type
warning_directive(normal execution continues), if the return value is true the execution continues as if no #warning directive has been found and the overall directive is replaced by a single newline.
template <typename ContextT, typename ContainerT>
bool found_error_directive(ContextT const& ctx,
ContainerT const &message);
The function found_error_directive is called whenever a #error directive has been encountered. Note, this function was added for the Boost V1.35.0 release.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The parameter message references the argument token sequence of the encountered #error directive.
If the return value is false, the library throws a preprocessor exception of the type
error_directive(normal execution continues), if the return value is true the execution continues as if no #error directive has been found and the overall directive is replaced by a single newline.
template <typename ContextT, typename ContainerT>
void found_line_drective(ContextT const& ctx,
ContainerT const &arguments, unsigned int line,
std::string const& filename);
The function found_line_directive is called whenever a #line directive has been encountered. Note, this function was added for the Boost V1.35.0 release.
The ctx parameter provides a reference to the context_type used during instantiation of the preprocessing iterators by the user.
The parameter arguments references the argument token sequence of the encountered #line directive.
The parameter line contains the recognized line number from the #line directive.
The parameter filename references the recognized file name from the #line directive (if there was one given).
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Copyright © 2003-2011 Hartmut Kaiser
Distributed under 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)
Last updated: Thursday, September 18, 2010 09:10