[strip -ST] Disable runtime stack trace dumping on Darwin when assert… #9311
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…s are disabled. This commit disables runtime stack trace dumping via dladdr on Darwin when asserts are disabled. This stack trace dumping was added as a way to improve the ability to debug the compiler for compiler developers. This is all well and good but having such a feature always enabled prevents us from reducing the size of the swift standard library by eliminating the swift nlist. rdar://31372220
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Roman reviewed this on the PR for master: #9170 |
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@swift-ci clean test |
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Build failed |
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The failure on Linux here was an unrelated llbuild failure. I am going to try again real quick. |
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@swift-ci please clean test linux platform. |
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Explanation: This PR changes the dladdr based backtraces to only be emitted when the standard library is compiled with assertions enabled. This restores the dladdr backtraces to their original purpose, namely as a tool meant for compiler authors. It additionally has a build system unit test to ensure that no parts of the runtime refer to dladdr. The reason we are doing this is so that we can safely strip -ST the swift standard library.
Scope: Without this, a stdlib that has strip -ST performed upon it will print out incorrect backtraces.
Radar: rdar://31372220
Risk: Minimal. This code only gets triggered upon a program already crashing. So only programs that are already crashing can be affected by a bug in this change. That being said, I think the testing here is relatively comprehensive, so I feel very confidant in this change.
Testing: I added compiler tests that verify that we produce correctly formed stack traces when the relevant settings are enabled and that we do not emit any stack traces when they are disabled. I tested with/without stdlib assertions locally and tested with assertions on the bots. The normal bots will double check the no-assertions case as well. I also added a build system unit test that ensures that no object files reference dladdr.