[llvm-dev] False Negatives Wunused-function in clang found by gcc

[David Blaikie via llvm-dev]

Not sure where the regression might've leaked in. But does seem to be
something to do with anonymous namespace support and member functions:
https://godbolt.org/z/zz8WP1



On Mon, Mar 1, 2021 at 5:12 PM Luke Benes via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
> By building llvm-project with gcc 7 and 10, I found multiple
> Wunused-function warnings that clang 11/12 missed.
>
> All of these warnings were recently introduced, and the authors fixed many
> of them.   Any ideas why clang misses so many of this category? And why the
> ones missed are recent changes to the llvm codebase?
>
> -Luke
>
>
> ==========
>
>  After dab953c8e44a2 with gcc 10.2.1, I see the following new warnings:
>
> [ 65%] Building CXX object
> lib/Linker/CMakeFiles/LLVMLinker.dir/IRMover.cpp.o
> /llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp:1600:1:
> warning: ‘std::pair<llvm::Value*, llvm::Value*>
> {anonymous}::DataFlowSanitizer::getShadowOriginAddress(llvm::Value*,
> llvm::Align, llvm::Instruction*)’ defined but not used [-Wunused-function]
>  1600 | DataFlowSanitizer::getShadowOriginAddress(Value *Addr, Align
> InstAlignment,
>       | ^~~~~~~~~~~~~~~~~
> /llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp:1510:6:
> warning: ‘void {anonymous}::DFSanFunction::setOrigin(llvm::Instruction*,
> llvm::Value*)’ defined but not used [-Wunused-function]
>  1510 | void DFSanFunction::setOrigin(Instruction *I, Value *Origin) {
>       |      ^~~~~~~~~~~~~
> /llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp:1476:8:
> warning: ‘llvm::Value* {anonymous}::DFSanFunction::getOrigin(llvm::Value*)’
> defined but not used [-Wunused-function]
>  1476 | Value *DFSanFunction::getOrigin(Value *V) {
>       |        ^~~~~~~~~~~~~
> /llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp:1469:8:
> warning: ‘llvm::Value* {anonymous}::DFSanFunction::getRetvalOriginTLS()’
> defined but not used [-Wunused-function]
>  1469 | Value *DFSanFunction::getRetvalOriginTLS() { return
> DFS.RetvalOriginTLS; }
>       |        ^~~~~~~~~~~~~
>
> FIX:
> https://github.com/llvm/llvm-project/commit/9524632fa2bf8c894e4aac27f03631a1915d84d3
>
> ==========
>
> After bc8e262afe83, with gcc 10.1 but not clang 11, I'm seeing:
>
> [ 21%] Building CXX object
> lib/MC/MCParser/CMakeFiles/LLVMMCParser.dir/MasmParser.cpp.o
> /llvm/lib/MC/MCParser/MasmParser.cpp:3836:6: warning: ‘bool
> {anonymous}::MasmParser::emitStructValue(const {anonymous}::StructInfo&)’
> defined but not used [-Wunused-function]
>  3836 | bool MasmParser::emitStructValue(const StructInfo &Structure) {
>       |      ^~~~~~~~~~
>
> FIX: https://reviews.llvm.org/D83898
>
> ==========
>
> In 931a68f26b9a3, I'm seeing the following warning with gcc7 and gcc10:
> [ 70%] Building CXX object
> lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocPBQP.cpp.o
> /llvm/lib/CodeGen/RegAllocFast.cpp:384:6: warning: ‘bool
> {anonymous}::RegAllocFast::verifyRegStateMapping(const
> {anonymous}::RegAllocFast::LiveReg&) const’ defined but not used
> [-Wunused-function]
>  bool RegAllocFast::verifyRegStateMapping(const LiveReg &LR) const {
>       ^~~~~~~~~~~~
>
> FIX: 0671a4c5087d40450603d9d26cf239f1a8b1367e
>
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