Question

How can I extract just the required functions from a pile of C source files? Is there a tool which can be used on GNU/Linux?

Preferably FOSS, but the GNU/Linux is a hard requirement.

Basically I got about 10 .h files; I’d like to grab part of the code and get the required variables from the header files. Then I can make a single small .h file corresponding to the code I’m using in another project.

My terms might not be 100% correct.

Answer 1

One tool that you may or may not be aware of is cscope. It can be used to help you.

For a given set of files (more on what that means shortly), it gives you these options:

Find this C symbol:
Find this global definition:
Find functions called by this function:
Find functions calling this function:
Find this text string:
Change this text string:
Find this egrep pattern:
Find this file:
Find files #including this file:

Thus, if you know you want to use a function humungous_frogmondifier(), you can find where it is declared or defined by typing its name (or pasting its name) after ‘Find this global definition’. If you then want to know what functions it calls, you use the next line. Once you’ve hit return after specifying the name, you will be given a list of the relevant lines in the source files above this menu on the screen. You can page through the list (if there are more entries than will fit on the screen), and at any time select one of the shown entries by number or letter, in which case cscope launches your editor on the file.

How about that list of files? If you run cscope in a directory without any setup, it will scan the source files in the directory and build its cross-reference. However, if you prefer, you can set up a list of files names in cscope.files and it will analyze those files instead. You can also include -I /path/to/directory on the cscope command line and it will find referenced headers in those directories too.

I’m using cscope 15.7a on some sizeable projects – depending on which version of the project, between about 21,000 and 25,000 files (and some smaller ones with only 10-15 thousand files). It takes about half an hour to set up this project (so I carefully rebuild the indexes once per night, and use the files for the day, accepting that they are a little less accurate at the end of the day). It allows me to track down unused stuff, and find out where stuff is used, and so on.

If you’re used to an IDE, it will be primitive. If you’re used to curses-mode programs (vim, etc), then it is tolerably friendly.