test: fix DWARF string_view linker error in blockfilter_tests #25120

Fix the following build error that I am seeing with Debian testing clang 15:

/usr/bin/ld: /usr/bin/ld: DWARF error: invalid or unhandled FORM value: 0x23
test/test_bitcoin-blockfilter_tests.o: in function `blockfilter_tests::blockfilters_json_test::test_method()':
blockfilter_tests.cpp:(.text+0x59d6): undefined reference to `ParseHex(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: blockfilter_tests.cpp:(.text+0x5e54): undefined reference to `ParseHex(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Unsure, possibly related to c1d165a8c2678c31ac or to changes in clang.

I'm really confused by this. Why would an explicit stringview{} be needed. Looks like the compiler thinks that ParseHex(const std::string&) is still defined where it's not. Normally this happens if the header and compilation is out of sync.

Did you build from a clean tree? Could this be some kind of ABI conflict between different C++ versions?

Yes, I suspected it was something on my end or a clang update (I updated today). Saw it several times after make distclean && ./autogen.sh && ./configure --enable-debug --with-incompatible-bdb --enable-werror --enable-c++20 --enable-suppress-external-warnings --enable-experimental-util-chainstate CC=clang CXX=clang++ && make clean && make. Anything else I should be doing to ensure a clean tree? Am building with gcc right now to compare.

@jonatack To be absolutely sure, you could clear the ccache cache (ccache -C) if you're using ccache.

The surest way to get a clean tree would be git clean -f -x -d (this literally wipes everything in the tree that doesn't belong to git, so be careful you don't have anything else in there)

But make clean should get rid of blockfilter_tests.o. Do you use ccache? maybe also ccache -C.

Thanks! The gcc build finished cleanly. Ran ccache -C and rebuilding with clang now.

Yes, I suspected it was something on my end or a clang update (I updated today).

Going to close, as this is pretty clearly a local issue. Feel free to continue discussion in regards to cleaning your git tree.

Clearing ccache did it. Closing and sorry for the noise.

Put the lesson to use with https://github.com/jonatack/jonatack.github.io/commit/5c3169fc29d40d9a6b63dc25b4467d2ddfa1f9b7 to add a basic troubleshooting section to https://jonatack.github.io/articles/how-to-compile-bitcoin-core-and-run-the-tests.