mgehre / xunused Goto Github PK

I tried to use this tool on a linux tool, but it fails to parse my compilation database.

Thanks for making this tool, it's been really helpful finding some dead code for us!

We have a lot of __attribute__((weak)) functions for test tracing and whatnot, is it possible to recognize these cases? I'm suspecting not since weak overrides happen during linkage but I'm not familiar enough with Clang's tooling to understand if it can figure that out.

Example that xunused thought was unused:

// main.c
void __attribute__((weak)) foo(void) {
}

int main(void) {
    foo();
}


// test_wrap.c

// This one was found to be "unused"
void foo(void) {
    // Does actual stuff
}

Matthias, in the README.md, I would add cd build before cmake ..

Clang is updated quite a lot.
It would be nice to support latest version (10).

Also, I don't think it's worth to have several versions if it's hard to maintain, so support of version 9 (and 8) is under question.

I downloaded the clang-8.0.0 binary distribution for Mac OS X and attempted to build, but it seems to complain about missing typeinfo in llvm:

/Applications/CMake.app/Contents/bin/cmake -E cmake_link_script CMakeFiles/xunused.dir/link.txt --verbose=1
/Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/bin/clang++ -std=c++17 -isysroot /Applications/Xcode_10.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -Wl,-search_paths_first -Wl,-headerpad_max_install_names CMakeFiles/xunused.dir/main.cpp.o -o xunused -L/Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib -Wl,-rpath,/Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib -lclangIndex -lclangTooling -lclangFrontend -lclangDriver -lclangSerialization -lclangParse -lclangSema -lclangAnalysis -lclangASTMatchers -lclangAST -lclangEdit -lclangLex -lclangBasic /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMX86AsmParser.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMSupport.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMOption.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMProfileData.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMX86Desc.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMX86AsmPrinter.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMX86Utils.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMMCDisassembler.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMObject.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMMCParser.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMMC.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMDebugInfoCodeView.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMDebugInfoMSF.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMBitReader.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMX86Info.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMCore.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMBinaryFormat.a /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMSupport.a -lz -lcurses -lm /Users/robb/clang+llvm-8.0.0-x86_64-apple-darwin/lib/libLLVMDemangle.a
Undefined symbols for architecture x86_64:
"typeinfo for llvm::ErrorInfoBase", referenced from:
typeinfo for llvm::ErrorInfo<llvm::ErrorList, llvm::ErrorInfoBase> in main.cpp.o
"typeinfo for clang::ASTConsumer", referenced from:
typeinfo for XUnusedASTConsumer in main.cpp.o
"typeinfo for clang::ast_matchers::MatchFinder::MatchCallback", referenced from:
typeinfo for FunctionDeclMatchHandler in main.cpp.o
"typeinfo for clang::ASTFrontendAction", referenced from:
typeinfo for XUnusedFrontendAction in main.cpp.o
"typeinfo for clang::tooling::FrontendActionFactory", referenced from:
typeinfo for XUnusedFrontendActionFactory in main.cpp.o
ld: symbol(s) not found for architecture x86_64
clang-8: error: linker command failed with exit code 1 (use -v to see invocation)
gnumake[2]: *** [xunused] Error 1
gnumake[1]: *** [CMakeFiles/xunused.dir/all] Error 2
gnumake: *** [all] Error 2
robb@Robs-MacBook-Pro:~/SkunkWorks/xunused/build (master)$

Do I need to build llvm from scratch with rtti turned on?

~/workspace/waa_dev/xunused \ue0b0 \ue0a0 * \ue0b0 build \ue0b0 make 765ms \ue0b3 Tue Oct 12 06:27:00 2021
Scanning dependencies of target xunused
[ 50%] Building CXX object CMakeFiles/xunused.dir/main.cpp.o
[100%] Linking CXX executable xunused
/bin/ld: CMakeFiles/xunused.dir/main.cpp.o:(.data.rel.ro._ZTI28XUnusedFrontendActionFactory[_ZTI28XUnusedFrontendActionFactory]+0x10): undefined reference to typeinfo for clang::tooling::FrontendActionFactory' /bin/ld: CMakeFiles/xunused.dir/main.cpp.o:(.data.rel.ro._ZTI21XUnusedFrontendAction[_ZTI21XUnusedFrontendAction]+0x10): undefined reference to typeinfo for clang::ASTFrontendAction'
/bin/ld: CMakeFiles/xunused.dir/main.cpp.o:(.data.rel.ro._ZTI18XUnusedASTConsumer[_ZTI18XUnusedASTConsumer]+0x10): undefined reference to typeinfo for clang::ASTConsumer' /bin/ld: CMakeFiles/xunused.dir/main.cpp.o:(.data.rel.ro._ZTI24FunctionDeclMatchHandler[_ZTI24FunctionDeclMatchHandler]+0x10): undefined reference to typeinfo for clang::ast_matchers::MatchFinder::MatchCallback'
/bin/ld: CMakeFiles/xunused.dir/main.cpp.o:(.data.rel.ro._ZTIN4llvm9ErrorInfoINS_9ErrorListENS_13ErrorInfoBaseEEE[_ZTIN4llvm9ErrorInfoINS_9ErrorListENS_13ErrorInfoBaseEEE]+0x10): undefined reference to `typeinfo for llvm::ErrorInfoBase'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/xunused.dir/build.make:108: xunused] Error 1
make[1]: *** [CMakeFiles/Makefile2:79: CMakeFiles/xunused.dir/all] Error 2
make: *** [Makefile:130: all] Error 2

Sometimes function or method is used just once and could be embedded into caller.

First attempt to use xunused, following the instructions in READ.me, fails:

$ bear --output /io/h.json -- ninja
$ /Gext/xunused/build/xunused /io/h.json 
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "/io/h.json"
No compilation database found in /io or any parent directory
fixed-compilation-database: Error while opening fixed database: No such file or directory
json-compilation-database: Error while opening JSON database: No such file or directory
Running without flags.