--- name: "tradcpp" section: "1" platform: "openbsd" package: "man" version: "8.0-current-20261101" release: "OpenBSD 8.0-current (2026-11-01)" platforms: ["openbsd"] url: "https://new.carta.tech/tradcpp" --- # tradcpp(1) traditional (K&R-style) C macro preprocessor ## NAME **tradcpp** – traditional (K&R-style) C macro preprocessor ## SYNOPSIS **tradcpp** \[**-options**\] \[*input-file* \[*output-file*\]\] ## DESCRIPTION The **tradcpp** command provides a traditional K&R-style C macro preprocessor. It is intended to be suitable for historical Unix uses of the preprocessor, such as **imake**, particularly those that depend on preservation of whitespace. The chief ways in which traditional cpp differs from Standard C are: - Macro arguments are expanded within quoted strings. There is no stringize operator. - There is no token pasting operator; tokens can be concatenated by placing comments between them. This process is also not limited to valid C language tokens. - Whitespace is preserved, and in particular tabs are not expanded into spaces. Furthermore, additional whitespace is not injected. ## OPTIONS **tradcpp** has many options, many of which are defined for compatibility with [gcc(1)](/gcc/1.md) or other compilers. Many of the options are not yet implemented. ### Common Options - **-C** Retain comments in output. - **-Dmacro\[=expansion\]** Provide a definition for the named macro. If no expansion is provided, the value “1” is used. Note that like many Unix compilers, **tradcpp** does not accept a space between the “D” and the macro name. - **-Ipath** Add the specified path to the main list of include directories. Note that like many Unix compilers, **tradcpp** does not accept a space between the “I” and the directory name. - **-nostdinc** Do not search the standard system include directories. - **-P** Suppress line number information in the output. Currently line number information is not generated at all and this option has no effect. - **-Umacro** Remove any existing definition for the named macro. Note that like many Unix compilers, **tradcpp** does not accept a space between the “U” and the macro name. - **-undef** Remove all predefined macros. ### Warning Options Warning options can be disabled or enabled by inserting, or not, the string “no-” between the “W” and the warning name. Herein the “**-Wno-**” form is shown for options that are enabled by default. - **-Wall** Turn on all warnings. The option **-Wno-all** disables only the warnings that are disabled by default. - **-w** Turn off all warnings. - **-Werror** Make warnings into fatal errors. - **-Wcomment** Warn about nested comments. - **-Wno-endif-labels** Don't warn about symbols attached to #endif directives. (The warning is currently not implemented.) - **-Wundef** Warn about undefined symbols appearing in #if and #elif expressions. - **-Wunused-macros** Warn about macros that are defined and never used. Not implemented. ### Depend Options - **-M** Generate dependency information for [make(1)](/make/1.md) on the standard output, instead of preprocessing. Not implemented. - **-MD** Like **-M** but skip system headers. Not implemented. - **-MM** Like **-M** but write the dependency information to a file named after the input file with extension *.d* and preprocess normally to standard output. Not implemented. - **-MMD** Like **-MM** but skip system headers. Not implemented. - **-MF** *file* Send dependency output to the named file instead of the default location. Not implemented. - **-MG** When generating dependency information, assume that missing files are generated instead of failing. Not implemented. - **-MP** Issue dummy rules for all include files. This prevents [make(1)](/make/1.md) from choking if an include file is removed. Not implemented. - **-MQ** *target* Same as **-MT** except that any [make(1)](/make/1.md) metacharacters appearing in the target are escaped. - **-MT** *target* Set the name of the [make(1)](/make/1.md) target appearing in the generated dependency information. The default is the name of the input file with its suffix replaced with the suffix for object files, normally *.o*. ### More Include Path Options - **-idirafter** *path* Add the specified path to the “afterwards” include path. This path is searched after all directories specified with **-I** and the standard system directories. Directories on this path are treated as containing system include files. - **-imacros** *file* Read in *file* prior to reading the main input file, and preprocess it, but throw away the output and retain only the macro definitions. - **-include** *file* Read in and preprocess *file* prior to reading the main input file. - **-iprefix** *prefix* Set the path prefix used with the **-iwithprefix** option. - **-iquote** *path* Add *path* to the list of directories searched for include directives written with quotes. This list is not searched for include directives written with angle brackets. - **-iremap** *string:replacement* Substitute *replacement* for *string* in the \_\_FILE\_\_ built-in macro. Not supported. - **-isysroot** *path* Use *path* as the “system root”, that is, the directory under which the standard system paths are found. - **-isystem** *path* Add *path* to the list of system include directories. This list is searched after the list given with *I*. Files found on this path are treated as system headers. - **-iwithprefix** *dir* Splice *dir* onto the prefix given with **-iprefix** and add this directory as if it were specified with **-idirafter**. - **-iwithprefixbefore** *dir* Like **-iwithprefix** but adds the result as if it were specified with **-I**. ### Diagnostic Options - **-debuglog** *file* Write a trace of actions and operations to *file* as the input is processed. Meant for debugging problems in complex substitution schemes fed to **tradcpp**, such as those used by **imake**. - **-dD** Dump all macro definitions, except for the predefined macros, after the normal preprocessing output. Not implemented. - **-dI** Dump all include directives along with the normal preprocessing output. Not implemented. - **-dM** Dump all macro definitions instead of the normal preprocessing output. Not implemented. - **-dN** Like **-dD** but emits only macro names and not the expansions. Not implemented. - **-H** Output a trace of the include tree as it gets processed. Not implemented. ### Other Options - **-CC** Retain comments in output. Same as **-C**, accepted for compatibility with [gcc(1)](/gcc/1.md). - **-fdollars-in-identifiers**, **-fno-dollars-in-identifiers** Enable (or disable, respectively) the use of the dollar sign in identifiers. Not implemented. - **-ftabstop=num** Set the tab width to the specified value, for reporting column positions in diagnostics. The default is 8. Not implemented. - **-std=standard** Ask **tradcpp** to conform to the named standard. The default, and the only supported value, is “krc”. - **-traditional** This option is accepted for compatibility with [gcc(1)](/gcc/1.md) and ignored. - **-x** *lang* Adjust the preprocessor for the given language. The only values accepted for *lang* are “assembler-with-cpp” and “c”, neither of which have any effect on the behavior of **tradcpp**. ## FILES The default list of directories searched for include files is: - */usr/local/include* - */usr/include* ## SEE ALSO [cc(1)](/cc/1.md), [cpp(1)](/cpp/1.md), [make(1)](/make/1.md) ## STANDARDS None. The whole point of a traditional cpp is that it reflects practices in pre-standardization implementations of C. Some information is available from the first edition of Kernighan and Ritchie. Much of the rest of the behavior is based on lore, pragmatism, material encountered in the wild, and comparison to other implementations. ## HISTORY The original version of **tradcpp** was written one evening in late 2010. This version had some problems and was put aside. The first working version was released in June 2013. ## BUGS Probably plenty.