This simple script helps in removing unnecessary includes from C/C++ files.
A huge code base or legacy code usually means that implementation files are full of includes pilled up over years. Likewise, creating a new project by forking an old one ends up with tons of leftovers.
The only thing you need is the full command that creates an object file.
The script systematically comments out one include file at once and recompiles source. When program/object file still compiles, then the commented out include is considered unneeded.
Caveat 1 (noticed by my colleague Leszek): such a mechanical way of removing includes may lead to creating indirect dependencies. Some symbols required by implementation might be provided (accidentally) by includes present in headers files. When one remove include from the implementation file, then later changes to the header file might break the compilation.
Caveat 2: the script doesn't interpret any other preprocessor directive
than #include. Conditional includes enabled by ifdefs will be removed
unconditionally.
Here's an example from my toy project https://github.com/WojciechMula/avx512popcnt-superoptimizer
The head of the main program:
$ head -n 15 avx512popcnt.cpp #include <cstdint> #include <cstdlib> #include <cstdio> #include <cassert> #include <vector> #include <memory> #include <random> #include <algorithm> #include <bitset> #include <sys/types.h> #include <unistd.h> #include "binary.cpp"
When run make, we capture the command which builds the program:
$ make avx512popcnt g++ -Wall -Wextra -pedantic -std=c++14 -O3 avx512popcnt.cpp -o lineavx512popcnt
Now the script comes:
$ python cleanup.py g++ -Wall -Wextra -pedantic -std=c++14 -O3 avx512popcnt.cpp -o avx512popcnt Checking compilation of avx512popcnt.cpp... OK Removing cstdint (1/12)... OK Removing cstdlib (2/12)... OK Removing cstdio (3/12)... OK Removing cassert (4/12)... not possible Removing vector (5/12)... OK Removing memory (6/12)... not possible Removing random (7/12)... not possible Removing algorithm (8/12)... OK Removing bitset (9/12)... OK Removing sys/types.h (10/12)... OK Removing unistd.h (11/12)... not possible Removing binary.cpp (12/12)... not possible avx512popcnt.cpp: not required cstdint, cstdlib, cstdio, vector, algorithm, bitset, sys/types.h avx512popcnt.cpp was updated
It turned out that eight includes weren't needed at all.
You can control behaviour of the script via a config file. The config
file must be located either in ~/.config/cleanup-headers/config.ini
or its path must be provided by the environment variable
CLEANUP_HEADERS_CONFIG. Please refer to the sample config.ini
for more details.