[compiler-rt/darwin] Disable building sanitizers on platforms without fork(). #83485
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The watchOS and tvOS sanitizers do not compile with publicly-available SDKs, failing on calls such as fork() and posix_spawn(). Updating the darwin_test_archs test program to include a call to fork() allows cmake to exclude those platforms when compiling runtimes. This allows public builds to enable watchOS/tvOS and compile builtins but not sanitizers.
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@delcypher per discussion on https://discourse.llvm.org/t/refined-controlling-of-options-in-distribution-builds-for-darwin/69976/2, the watchOS/tvOS sanitizer runtimes cannot build against public SDKs. I don't need to build sanitizers locally, but I would like to have the watchOS builtins library, and currently COMPILER_RT_ENABLE_WATCHOS=ON tries to build both (and fails). Adding a test for |
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I think this is a good approach (after addressing the below comment).
From what I can tell, we only need fork() to invoke the external llvm-symbolizer. Maybe in the future we could just not do that on systems where fork() isn't available and require people to symbolize on the host machine. But that can be a separate PR done by someone else at some point, and until then this seems like a good improvement to me :)
(I'll wait a day or two for @delcypher to comment as well.)
| @@ -116,7 +116,7 @@ function(darwin_test_archs os valid_archs) | |||
| if(NOT TEST_COMPILE_ONLY) | |||
| message(STATUS "Finding valid architectures for ${os}...") | |||
| set(SIMPLE_C ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.c) | |||
| file(WRITE ${SIMPLE_C} "#include <stdio.h>\nint main(void) { printf(__FILE__); return 0; }\n") | |||
| file(WRITE ${SIMPLE_C} "#include <stdio.h>\nint main(void) { printf(__FILE__); fork(); return 0; }\n") | |||
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I think this needs an #include <unistd.h>\n too, else it will disable the sanitizers on macOS too:
% cat test.c
#include <stdio.h>
int main() { fork(); }
% clang -c test.c
test.c:3:14: error: call to undeclared function 'fork'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
int main() { fork(); }
^
1 error generated.
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Please put into title that this is Darwin. |
nico
changed the title
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@jroelofs fyi |
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This seems harmless enough, I'll go ahead and merge this. Others: Please shout if this causes issues! |
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FWIW, last time I looked at this a few years ago, from what I could tell, tvOS/watchOS do have fork/etc calls. They're marked as "unavailable", but that's only an issue with the headers. Apple actually does ship these libraries (containing calls to fork/etc!), so I suspect they internally have a build option which disables the "unavailable" annotations. It seemed that modifying the So, if someone wanted to, they could probably fix the compiler-rt cmake to support building the sanitizer runtimes on these platforms just by creating a wrapper |
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Does having the sanitizers runtimes help you if you can't use them though? As mentioned further up, the |
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I think you can use sanitizer libs you build...can't you? W.r.t. fork/exec, certainly it is denied by the kernel at runtime on any "normal" i/tv/watch OS device, but I suspect it probably works fine in the simulator. Don't know whether that gets used in practice or not. |
I'd expect them to be killed once the Taking a step back, is this causing problems on your end, or is this more a hypothetical situation we're discussing? :) |
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No problems -- I was actually just trying to record information that was in my head, in case someone wanted to revisit this in the future. |
The watchOS and tvOS sanitizers do not compile with publicly-available SDKs, failing on calls such as fork() and posix_spawn(). Updating the darwin_test_archs test program to include a call to fork() allows cmake to exclude those platforms when compiling runtimes. This allows public builds to enable watchOS/tvOS and compile builtins but not sanitizers.