Disable loading of libLLVM at runtime #7499
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Context: xamarin/monodroid@d887d87d8f Context: llvm/llvm-project@c10ca90 Disable loading of `libLLVM.so` on Android API 21 and newer, because the symbol we're looking for is no longer present in the library on those Android versions. The hack was implemented on April 8, 2014: Disable LLVM signal handlers. Fixes #18016. This happens when RenderScript needs to be compiled. See https://bugzilla.xamarin.com/show_bug.cgi?id=18016 This happens only on first run of the app. LLVM is used to compiled the RenderScript scripts. LLVM, been a nice and smart library installs a ton of signal handlers and don't chain at all, completely breaking us. This is a hack to set llvm::DisablePrettyStackTrace to true and avoid this source of signal handlers. LLVM commit referenced above made the stack pretty print feature opt-in instead of opt-out, removing the `DisablePrettyStackTrace` symbol. Thus, LLVM no longer installs the signal handlers mentioned above and, in effect, doesn't break us anymore. Consequently, the code is completely disabled for .NET builds, since they build against API 21. For classic builds we now check the API level and load the library only if running on API < 21.
grendello
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* main: [monodroid] Disable loading of libLLVM at runtime (dotnet#7499) Bump to dotnet/installer@8c1708f 8.0.100-alpha.1.22526.2 (dotnet#7497)
grendello
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* main: [Tests] Replace azurestorage with a github repo. (dotnet#7524) Bump to xamarin/Java.Interop/main@5318261 (dotnet#7502) [build] fix 8.0.100-alpha.1 version band (dotnet#7500) [monodroid] Disable loading of libLLVM at runtime (dotnet#7499) Bump to dotnet/installer@8c1708f 8.0.100-alpha.1.22526.2 (dotnet#7497)
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Context: xamarin/monodroid@d887d87d8f Context: llvm/llvm-project@c10ca90 Way back in 2014-Feb-26, private bug [#18016][0] was filed against Xamarin.Android 4.10.2: when a project contained RenderScript and ran on an Android 4.0.4 device, it could eventually hang. No exception, no error message, no nothing. After investigation, the cause of the hang was that the RenderScript compiler would use the same Unix signals as the Mono for Android GC, and did not properly chain those signals. Thus, if the on-device RenderScript compiler hit particular code paths which caused it to register those Unix signals, the Mono for Android GC would no longer work from that point onward. It was determined that the `llvm::DisablePrettyStackTrace` global variable within `libLLVM.so` could control this behavior. The "fix"/workaround was to *prevent* the RenderScript compiler from subscribing to those Unix signals by: 1. Loading `libLLVM.so` at runtime, 2. Looking for the symbol `_ZN4llvm23DisablePrettyStackTraceE`, which is the name mangled form of `bool llvm::DisablePrettyStackTrace`. 3. Set the value to 1/`true`. xamarin/monodroid@d887d87d8f commit message contents: > Disable LLVM signal handlers. Fixes #18016. > > This happens when RenderScript needs to be compiled. > See https://bugzilla.xamarin.com/show_bug.cgi?id=18016 > > This happens only on first run of the app. LLVM is used to compiled > the RenderScript scripts. LLVM, been a nice and smart library > installs a ton of signal handlers and don't chain at all, completely > breaking us. > > This is a hack to set llvm::DisablePrettyStackTrace to true and > avoid this source of signal handlers. The `llvm::DisablePrettyStackTrace` variable was *removed* from LLVM in 2013-Nov-3 via llvm/llvm-project@c10ca903, but Android continued to redistribute a version of LLVM which contained that symbol until Android 5.0 / API-21. Update `MonodroidRuntime::disable_external_signal_handlers()` to do nothing for .NET 6+ -- as .NET 6 has API-21 as a minimum API level -- and update Classic Xamarin.Android to only look for `libLLVM.so!_ZN4llvm23DisablePrettyStackTraceE` on pre-API-21 targets. This removes the warning message: Failed to load shared library 'libLLVM.so' when running .NET Android apps. [0]: https://bugzilla.xamarin.com/18/18016/bug.html
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Context: https://github.com/xamarin/monodroid/commit/d887d87d8f
Context: llvm/llvm-project@c10ca90
Disable loading of
libLLVM.soon Android API 21 and newer, because the symbol we're looking for is no longer present in the library on those Android versions.The hack was implemented on April 8, 2014:
LLVM commit referenced above made the stack pretty print feature opt-in instead of opt-out, removing the
DisablePrettyStackTracesymbol. Thus, LLVM no longer installs the signal handlers mentioned above and, in effect, doesn't break us anymore.Consequently, the code is completely disabled for .NET builds, since they build against API 21.
For classic builds we now check the API level and load the library only if running on API < 21.