[clang] [llvm] [sancov] Introduce optional callback for stack-depth tracking (PR #138323)

[Marco Elver via cfe-commits]

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@@ -2361,6 +2361,13 @@ def fsanitize_coverage_ignorelist : Joined<["-"], "fsanitize-coverage-ignorelist
     HelpText<"Disable sanitizer coverage instrumentation for modules and functions "
              "that match the provided special case list, even the allowed ones">,
     MarshallingInfoStringVector<CodeGenOpts<"SanitizeCoverageIgnorelistFiles">>;
+def fsanitize_coverage_stack_depth_callback_min_EQ
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melver wrote:

Is there other user facing documentation besides this?

There's https://clang.llvm.org/docs/SanitizerCoverage.html - but I don't see it have an entry for stack-depth yet.

I'm asking because it's not entirely clear by looking at this where the callback is done. I can see that it's after allocas at entry. Like the inline version, in the callback you can then do __builtin_frame_address(). Are there other caveats (allocas in later branches, etc.)?

https://github.com/llvm/llvm-project/pull/138323