mstorsjo wrote:
This PR seems to have broken ASAN in mingw configurations. The symptoms seem to
be that the ASAN DLL just locks up, hard, when the process is loaded. (Or more
precisely, has entered some infinite loop.)
I tried attaching to such a hung process with windbg, and it's showing this:
```
Break-in sent, waiting 30 seconds...
WARNING: Break-in timed out, suspending.
This is usually caused by another thread holding the loader lock.
```
And a backtrace that looks like this:
```
libclang_rt_asan_dynamic_x86_64!_asan_default_options__dll
libclang_rt_asan_dynamic_x86_64!_asan_default_options__dll+0xa17
libclang_rt_asan_dynamic_x86_64!_sanitizer_register_weak_function+0xd2
stacksmash_asan+0x1dad
stacksmash_asan+0x16b7
stacksmash_asan+0x20e3
ntdll!LdrpCallInitRoutine+0x6f
ntdll!...
```
(Side note; the PR seems to have added a bunch of new files with CRLF newlines
- it'd be nice to clean this up.)
To repro the issue for yourself, you can do the following:
1. Download and unzip
https://github.com/mstorsjo/llvm-mingw/releases/download/20240903/llvm-mingw-20240903-ucrt-x86_64.zip,
and add the `llvm-mingw-<version>-ucrt-x86_64\bin` directory to your `%PATH%`
within a terminal
2. Configure a build of compiler-rt with the following parameters: `cmake
..\compiler-rt -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=clang
-DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER_TARGET=x86_64-w64-windows-gnu
-DCOMPILER_RT_DEFAULT_TARGET_ONLY=TRUE -DCOMPILER_RT_USE_BUILTINS_LIBRARY=TRUE
-DSANITIZER_CXX_ABI=libc++
-DCMAKE_INSTALL_PREFIX=c:\code\llvm-mingw-20240903-ucrt-x86_64\lib\clang\19`
3. Build and install (on top of the newly unpacked toolchain), `ninja install`
4. Copy the newly built asan DLL into the current directory, `copy /y
lib\windows\libclang_rt.asan_dynamic-x86_64.dll .`
5. Compile a trivial hello world, like
https://github.com/mstorsjo/llvm-mingw/blob/master/test/hello.c (really any
snippet will do), with asan `clang hello.c -o hello.exe -fsanitize=address`
6. Try to run `hello.exe`, which hangs.
It's possible to reproduce the same by building and running the whole
compiler-rt testsuite as well, but that's a bit trickier to set up for this
configuration.
Surprising side note; when I tried the repro procedure above, building
compiler-rt with a slightly older Clang release, and 18.x version, the built
ASAN seems to not hang. I'm not sure if this is a functional difference, or if
it just so happens to link things slightly differently so whatever issue there
is seems to just not happen.
This commit is kinda complex, as it not only removes the static asan
configuration (which never was involved in mingw use cases before), but I guess
also sets things up so the dynamic asan can be used even when linking the CRT
statically?
This issue has caused my nightly builds to start failing:
https://github.com/mstorsjo/llvm-mingw/actions/runs/10803005560
https://github.com/llvm/llvm-project/pull/107899
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