[llvm-dev] How to port symcc to clang/llvm-13?

[Alberto Barbaro via llvm-dev]

Hi Min-Yih,
thanks for your email. I have searched online on how to build clang plugins
and I found [1]. I wanted to use the example that prints all the function
names but, despite the fact that I followed the instructions, I could not
compile it :)

I searched again and I found [2] and hopefully In this case I could build
and run the basic hello-world example. I then tried to just replace the
HelloWorld.cpp with the example that print the functions names but no luck.
I compile but I have an error message. The following paragraph shows the
entire test:

➜  build git:(main) ✗ make
Scanning dependencies of target HelloWorld
[ 50%] Building CXX object CMakeFiles/HelloWorld.dir/HelloWorld.cpp.o
[100%] Linking CXX shared library libHelloWorld.so
[100%] Built target HelloWorld
➜  build git:(main) ✗ clang-13 -cc1 -load ./libHelloWorld.so -plugin
hello-world $CLANG_TUTOR_DIR/test/HelloWorld-basic.cpp
➜  build git:(main) ✗ $Clang_DIR/bin/clang -cc1 -load ./libHelloWorld.so
-plugin hello-world $CLANG_TUTOR_DIR/test/HelloWorld-basic.cpp
(clang-tutor)  file:
/home/alberto/Desktop/projects/llvm/clang-tutor//test/HelloWorld-basic.cpp
(clang-tutor)  count: 3
➜  build git:(main) ✗ cd ..
➜  HelloWorld git:(main) ✗ wget
https://raw.githubusercontent.com/llvm/llvm-project/main/clang/examples/PrintFunctionNames/PrintFunctionNames.cpp
--2021-12-17 06:45:54--
https://raw.githubusercontent.com/llvm/llvm-project/main/clang/examples/PrintFunctionNames/PrintFunctionNames.cpp
Resolving raw.githubusercontent.com (raw.githubusercontent.com)...
185.199.110.133, 185.199.109.133, 185.199.108.133, ...
Connecting to raw.githubusercontent.com
(raw.githubusercontent.com)|185.199.110.133|:443...
connected.
HTTP request sent, awaiting response... 200 OK
Length: 4504 (4.4K) [text/plain]
Saving to: ‘PrintFunctionNames.cpp’

PrintFunctionNames.cp 100%[========================>]   4.40K  --.-KB/s
 in 0s

2021-12-17 06:45:54 (11.3 MB/s) - ‘PrintFunctionNames.cpp’ saved [4504/4504]

➜  HelloWorld git:(main) ✗ mv HelloWorld.cpp HelloWorld.cpp.backup
➜  HelloWorld git:(main) ✗ mv PrintFunctionNames.cpp HelloWorld.cpp
➜  HelloWorld git:(main) ✗ rm -rf build
➜  HelloWorld git:(main) ✗ take build
➜  build git:(main) ✗ cmake ../
-- The C compiler identification is GNU 10.2.1
-- The CXX compiler identification is GNU 10.2.1
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test Terminfo_LINKABLE
-- Performing Test Terminfo_LINKABLE - Success
-- Found Terminfo: /usr/lib/x86_64-linux-gnu/libtinfo.so
-- Found ZLIB: /usr/local/lib/libz.so (found version "1.2.11")
-- Configuring done
-- Generating done
-- Build files have been written to:
/home/alberto/Desktop/progetti/llvm/clang-tutor/HelloWorld/build
➜  build git:(main) ✗ make
Scanning dependencies of target HelloWorld
[ 50%] Building CXX object CMakeFiles/HelloWorld.dir/HelloWorld.cpp.o
[100%] Linking CXX shared library libHelloWorld.so
[100%] Built target HelloWorld
➜  build git:(main) ✗ $Clang_DIR/bin/clang -cc1 -load ./libHelloWorld.so
-plugin hello-world $CLANG_TUTOR_DIR/test/HelloWorld-basic.cpp
error: unable to find plugin 'hello-world'
➜  build git:(main) ✗

Any idea on how to solve it? I think a little github repo with an example
on how to do it as standalone project would be beneficial to others as well.

Thanks a lot for all
Alberto

[1] https://clang.llvm.org/docs/ClangPlugins.html
[2] https://github.com/banach-space/clang-tutor

Il giorno ven 17 dic 2021 alle ore 01:11 Min-Yih Hsu <minyihh at uci.edu> ha
scritto:

> It’s a lot easier to load custom pass plugins into clang with the new
> PassManager actually:
> ```
> clang -fpass-plugin=<path to plugin> ...
> ```
> Note that <path to plugin> needs to be an absolute path.
>
> -Min
>
> On Dec 17, 2021, at 6:38 AM, Alberto Barbaro via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi all,
> Few days ago I have discovered the symcc[1] project. This project, via an
> llvm pass, is able to modify the IR code and to inject calls to a backend
> which allows symbolic execution. I can use it with clang/llvm 11 but not
> with the version 13.
>
> I was wondering if maybe the new pass manager uses llvm passes in a
> different way .. so I have created a small pass which injects a call to
> printf in each function and I'm able to use it via opt. Now my question is:
> is it possible to run the same pass via clang and just obtain the modified
> IR code? I'd like to avoid to use opt if not mandatory. Is it possible to
> do it or the new pass manager forces me to use opt?
>
> How would you fix this situation in symcc?
>
> If someone could tell me how to load a ModulePass in clang-13 would be
> great.
>
> Thanks a lot
> Alberto
>
> [1] https://github.com/eurecom-s3/symcc
>
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