Extracting C / C++ function prototypes

Question

I want to do this:

extract_prototypes file1.c file2.cpp file3.c

and have whatever script/program print a nice list of function prototypes for all functions defined in the given C / C++ files. It must handle multi-line declarations nicely.

Is there a program that can do this job? The simpler the better.

EDIT: after trying to compile two C programs, bonus points for something that uses {perl, python, ruby}.

Answer 1

I use ctags

# p = function declaration, f = function definition
ctags -x --c-kinds=fp /usr/include/hal/libhal.h

Also works with C++

ctags -x --c++-kinds=pf --language-force=c++ /usr/include/c++/4.4.1/bits/deque.tcc

---

Note, you may need to add include paths, do this using the -I /path/to/includes.

Answer 2

The tool cproto does what you want and allows to tune the output to your requirements.

Note: This tool also only works for C files.

Answer 3

I use ctags and jq

ctags --output-format=json --totals=no --extras=-F --fields=nP file1.c |
jq -sr 'sort_by(.line) | .[].pattern | ltrimstr("/^") | rtrimstr("$/") | . + ";"'

Answer 4

If you have universal-ctags (https://ctags.io), --_xformat option may be useful though you need sed and tr commands to get what you want.

$ cat input.c 
struct object *new_object (struct
                           /* COMMENT */
                           param
                           /* IGNORE ME */
                           *p)
{
    return NULL;
}
int main (void)
{
    return 0;
}
$ ./ctags -o - --kinds-C=f --kinds-C++=f -x --_xformat='%{typeref} %{name} %{signature};' input.c | tr ':' ' ' | sed -e 's/^typename //'
struct object * new_object (struct param * p);
int main (void);
$

This is similar to the answer posted by Steve Ward but this one requires sed, and tr instead of jq.

Answer 5

http://cfunctions.sourceforge.net

(This only does C and a limited subset of C++. Disclaimer: this is my program.)

Answer 6

I used to use doxygen to generate documentation for my C++ code. I am not an expert, but i think you can use doxygen to generate some sort of index file of the function prototypes.

Here is a thread of someone asking a similar question

Answer 7

If you format your comments suitably, you could try DOxygen. In fact, if you've not tried it before I'd recommend giving it a go anyway - it will produce inheritance graphs as well as full member function lists and descriptions (from your comments).

Answer 8

gccxml is interesting, but it print a xml tree. You need to extract information about class, functions, types, and even the specialized templates of class and functions. gccxml use parser of GCC, so you don't need to do the worst job wich is parsing C++ file, and you are 100% sure that it's what probably the best compilator understand.

Answer 9

In more modern versions of GCC, you can also use -aux-info to get this information when writing C code. See here.

Here's a sample of what the output looks like:

/* src/main.c:30:NC */ static void usage (const char *);
/* src/main.c:32:NF */ extern int main (int argc, char **argv); /* (argc, argv) int argc; char **argv; */
/* src/main.c:57:NF */ static void usage (const char *prog_name); /* (prog_name) const char *prog_name; */

Answer 10

gcc-xml might help, although as it is, it only does half the job you want. You'll need some processing of the XML output

Answer 11

You can run the source file through this program:

/* cproto_parser.c */
#include <stdio.h>                           
int main (void)                              
{                                            
    int c;                                   
    int infundef = 0;                        
    int nb = 0,                              
        np = 0;                              
    while((c=getc(stdin))!=EOF){             
        if(c=='{'){                          
            if((np==0)&&(nb==0)){infundef=1;}
            nb++;                            
        }                                    
        if (infundef==0) {putc(c,stdout);}   
        if(c=='}'){                          
            if((np==0)&&(nb==1)){infundef=0;}
            nb--;                            
        }                                    
        if(c=='('){np++;}                    
        if(c==')'){np--;}                    
    }                                        
    return 0;                                
}                    

Run through the preprocessor to get rid of comments. If you have unmatched braces due to #ifdefs you have to set defines, include files to make it not so.

e.g., cc cproto_parser.c -o cproto_parser; cc -E your_source_file.c|./cproto_parser