Header file inclusion static analysis tools?

Question

A colleague recently revealed to me that a single source file of ours includes over 3,400 headers during compile time. We have over 1,000 translation units that get compiled in a build, resulting in a huge performance penalty over headers that surely aren't all used.

Are there any static analysis tools that would be able to shed light on the trees in such a forest, specifically giving us the ability to decide which ones we should work on paring out?

UPDATE

Found some interesting information on the cost of including a header file (and the types of include guards to optimize its inclusion) here, originating from this question.

Answer 1

The output of gcc -w -H <file> might be useful (If you parse it and put some counts in) the -w is there to suppress all warnings, which might be awkward to deal with.

From the gcc docs:

-H

Print the name of each header file used, in addition to other normal activities. Each name is indented to show how deep in the #include stack it is. Precompiled header files are also printed, even if they are found to be invalid; an invalid precompiled header file is printed with ...x and a valid one with ...!.

The output looks like this:

. /usr/include/unistd.h .. /usr/include/features.h ... /usr/include/bits/predefs.h ... /usr/include/sys/cdefs.h .... /usr/include/bits/wordsize.h ... /usr/include/gnu/stubs.h .... /usr/include/bits/wordsize.h .... /usr/include/gnu/stubs-64.h .. /usr/include/bits/posix_opt.h .. /usr/include/bits/environments.h ... /usr/include/bits/wordsize.h .. /usr/include/bits/types.h ... /usr/include/bits/wordsize.h ... /usr/include/bits/typesizes.h .. /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/include/stddef.h .. /usr/include/bits/confname.h .. /usr/include/getopt.h . /usr/include/stdio.h .. /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/include/stddef.h .. /usr/include/libio.h ... /usr/include/_G_config.h .... /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/include/stddef.h .... /usr/include/wchar.h ... /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/include/stdarg.h .. /usr/include/bits/stdio_lim.h .. /usr/include/bits/sys_errlist.h Multiple include guards may be useful for: /usr/include/bits/confname.h /usr/include/bits/environments.h /usr/include/bits/predefs.h /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h /usr/include/bits/typesizes.h /usr/include/gnu/stubs-64.h /usr/include/gnu/stubs.h /usr/include/wchar.h 

Answer 2

If you are using gcc/g++, the -M or -MM option will output a line with the information you seek. (The former will include system headers while the latter will not. There are other variants; see the manual.)

$ gcc -M -c foo.c foo.o: foo.c /usr/include/stdint.h /usr/include/features.h \   /usr/include/sys/cdefs.h /usr/include/bits/wordsize.h \   /usr/include/gnu/stubs.h /usr/include/gnu/stubs-64.h \   /usr/include/bits/wchar.h 

You would need to remove the foo.o: foo.c at the beginning, but the rest is a list of all headers that the file depends on, so it would not be too hard to write a script to gather these and summarize them.

Of course this suggestion is only useful on Unix and only if nobody else has a better idea. :-)