[win/asan] Failing to get instruction size of ucrtbase.dll strstr

[agudbrand]

Asan reports:

==44184==interception_win: unhandled instruction at 0x7ffff8c23a40: 44 0f b6 1a 4c 8b d2 48

Happening on a locally built llvm, compiling with clang++. When I initially built LLVM it wasn't working, but I rebuilt it and it started working, but I needed to rebuild it again and now it no longer works. I am building from this commit and the CMake command used to configure the build files was:

cmake ../../src/llvm -G "Visual Studio 17 2022" -DLLVM_OPTIMIZED_TABLEGEN=ON "-DLLVM_ENABLE_PROJECTS=clang;lld;compiler-rt;clang-tools-extra" -DCMAKE_BUILD_TYPE=Release -DLLVM_INCLUDE_TESTS=OFF  

LLVM was compiled using MSVC 2022 17.12.4. Asan is compiled into the program using -fsanitize=address.

[bernhardu]

Hello, the commit you are building from should already include this line, so this instruction should be supported.

llvm-project/compiler-rt/lib/interception/interception_win.cpp

Lines 905 to 906 in dd3edc8

	case 0x1ab60f44: // 44 0f b6 1a : movzx r11d, BYTE PTR [rdx]
	return 4;

Could you maybe double check if you are using the right clang++ binary?

[agudbrand]

Oh, I apologize for my confusion. It seems my LLVM clone was on a HEAD revision that must have been out of date. I unfortunately cannot test if swapping it to main has fixed it yet as I've found that I need to dynamically link the c runtime in my stuff so I can build a shared library and now when I try to link asan it gives me duplicate symbol errors on malloc, free, etc. I will let you know if that was the issue once I get my stuff working again.

[agudbrand]

It seems that its impossible for me to get asan to link when dynamically linking the crt under windows, so I cannot properly test if it works now, but I will assume that the issue was just that I was unknowingly building an outdated llvm, so I'll close this issue.