getCppDefines: Compute the C/C++ pre-processor macro definitions

In omegahat/RGCCTranslationUnit: R interface to GCC source code information

Description

The getCppDefines function attempts to get the definitions of the pre-processor definitions from one or more header/source files by using GCC's ability to emit the table of macro definitions. It compares the collection of defined symbols to that without the source file (but with specified system header files) so as to find the ones that are actually defined within the user-level source files and not the system definitions. These can then be processed further to organize them into different categories using, e.g. processDefines and filterMacros.

Usage

getCppDefines(fileName = character(), cppFlags = "", cpp = "g++",
               flags = "-E -P -dM", sysIncludes = c("stdlib.h", "stdio.h"))

Arguments

fileName	the name of the C/C++ source file which is to be passed to the pre-processor. This is the file containing the code for which we want to extract the pre-processor definitions.
cppFlags	any extra C/C++ pre-processor flags needed for processing filename. These can be literal strings giving the flags or alternatively, a shell command that computes the flags within the execution of the shell command to run the pre-processor. Such dynamic flags should be enclosed within double quotes with the command in back-quotes, e.g. "`wx-config --cflags`". And this is platform-specific, working on Mac OS X and UNIX/Linux.
cpp	the name of the C/C++ pre-processor. By default, we use the GCC C++ compiler and instruct it to only run the pre-processor phase of the compilation via the flags arguments. One can specify an executable and flags here as the strings are pasted together to form the command. By separating the flags and the executable, we make it easier to specify a different executable, e.g. in a different location/directory than the default.
flags	additional flags or command line-arguments to be passed to the pre-processor command (i.e. cpp). These control how the processor is invoked relative to executable which may be the regular compiler.
sysIncludes	a character vector which gives the names of the system-level include files which are to be treated as the baseline. These are used by first computing all the macro definition symbols that occur in these files (and the compiler/pre-processor itself) and removing these from the symbols that are found when we apply the pre-processor to the the user-specified source file, i.e., fileName.

Details

This uses the GCC suite's ability to dump the table of pre-processor symbols via command line arguments.

Value

A character vector giving the set of macro definitions as lines of the form "#define SYM definition". Macros that have multi-line definitions will have multiple entries in this vector with the subsequent lines of the definition being successive elements in the result. These are manipulated and pulled into single definitions using processDefines.

Author(s)

Duncan Temple Lang

References

The GCC pre-processor

See Also

processDefines

omegahat/RGCCTranslationUnit documentation built on May 24, 2019, 1:53 p.m.