no-exceptions

src/behavior-considered-undefined.md

@@ -51,9 +51,12 @@ code.
 * Invoking undefined behavior via compiler intrinsics.
 * Executing code compiled with platform features that the current platform
   does not support (see [`target_feature`]), *except* if the platform explicitly documents this to be safe.
-* Calling a function with the wrong call ABI or unwinding from a function with the wrong unwind ABI.
+* Calling a function with the wrong call ABI or unwinding from a function with the wrong unwind ABI
 * Calling a foreign (e.g. C++) function that unwinds (`throw`s) via a function
   declaration or pointer declared with a non-unwinding ABI such as `"C"`
+* Calling a Rust `extern` function that unwinds (with `extern "C-unwind"` or
+  another ABI that permits unwinding) from a runtime that does not support
+  unwinding, such as code compiled with GCC or Clang using `-fno-exceptions`
 * Deallocating a Rust stack frame without executing destructors
   for local variables owned by the stack frame. This can occur
   with C functions like `longjmp`.