CFiddle makes it easy to ask and answers questions about the compilation and execution of smallish programs written in C or C++.
Project description
CFiddle: A Tool For Studying Small Compiled Programs
CFiddle is a tool for studying the compilation and execution of smallish programs written in compiled languages like C, C++, or Go. If you want to know what the compiler does to your code and why your code is slow, CFiddle can help.
It makes it easy to ask and answer interesting questions about what happens to programs as they go from source code to running program. CFiddle can run on its own, but it is built to work with Jupyter Notebook/Jupyter Lab to support interactive exploration.
It's features include:
- Support for compiled languages like C, C++, and Go.
- Control Flow Graph (CFG) generation from compiled code.
- Easy support for varying build-time and run-time paremeters.
- Easy, unified parameter and data gathering across building and running code.
- Works great with Pandas and Jupyter Notebook/Lab.
The best way to learn about CFiddle is to try it. You can run the examples (this can take a while to load).
Or run it locally with Docker:
docker run -it --publish published=8888,target=8888 stevenjswanson/cfiddle:latest jupyter lab --LabApp.token=''
and then visit http://localhost:8888/lab/tree/README.ipynb.
You can also read the documentation.
Examples
What Does a for
loop look like in assembly?
>>> from cfiddle import *
>>> sample = code(r"""
... extern "C"
... int loop() {
... int sum = 0;
... for(int i = 0; i < 10; i++) {
... sum += i;
... }
... return sum;
... }
... """)
>>> asm = build(sample)[0].asm("loop")
>>> print(asm) # doctest: +SKIP
loop:
.LFB0:
.cfi_startproc
endbr64
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq %rsp, %rbp
.cfi_def_cfa_register 6
movl $0, -8(%rbp)
movl $0, -4(%rbp)
.L3:
cmpl $9, -4(%rbp)
jg .L2
movl -4(%rbp), %eax
addl %eax, -8(%rbp)
addl $1, -4(%rbp)
jmp .L3
.L2:
movl -8(%rbp), %eax
popq %rbp
.cfi_def_cfa 7, 8
ret
.cfi_endproc
Or, if you prefer a CFG:
>>> build(sample)[0].cfg("loop", "readme_loop.png")
'readme_loop.png'
What Does -O3
Do To That Loop?
>>> asm = build(sample, build_parameters=dict(OPTIMIZE="-O3"))[0].asm("loop")
>>> print(asm) # doctest: +SKIP
loop:
.LFB0:
.cfi_startproc
endbr64
movl $45, %eax
ret
.cfi_endproc
Local Installation
CFiddle depends on some system packages and python's wheel
. Setup a virtual environment:
python -m venv cfiddle-venv
So you can install the system packages CFiddle needs. Check
install_prereqs.sh
to see what this includes. It uses apt-get
.
sudo bash
. cfiddle-venv/bin/activate
./install_prereqs.sh
exit
Install cfiddle:
. cfiddle-venv/bin/activate
pip install .
Run the tests:
make test
Common Problems
CFiddle needs LD_LIBRARY_PATH
set properly to work, and it can't set it itself reliably. If you get
OSError: libcfiddle.so: cannot open shared object file: No such file or directory
You can update LD_LIBRARY_PATH
with:
$(set-cfiddle-ld-path)
Saving Your Work
If you want to save changes you make to any of the examples, you'll need to run docker something like this:
docker run -it --publish published=8888,target=8888 --mount type=bind,source=$HOME,dst=/home/jovyan -w /home/jovyan/cfiddle_work/cfiddle stevenjswanson/cfiddle:latest jupyter lab --LabApp.token=''
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