Setjmp/Longjmp (SJLJ) based exception handling uses LLVM intrinsics + llvm.eh.sjlj.setjmp and + llvm.eh.sjlj.longjmp to + handle control flow for exception handling.
+ +For each function which does exception processing, be it try/catch blocks + or cleanups, that function registers itself on a global frame list. When + exceptions are being unwound, the runtime uses this list to identify which + functions need processing.
+ +
Landing pad selection is encoded in the call site entry of the function + context. The runtime returns to the function via + llvm.eh.sjlj.longjmp, where + a switch table transfers control to the appropriate landing pad based on + the index stored in the function context.
+ +In contrast to DWARF exception handling, which encodes exception regions + and frame information in out-of-line tables, SJLJ exception handling + builds and removes the unwind frame context at runtime. This results in + faster exception handling at the expense of slower execution when no + exceptions are thrown. As exceptions are, by their nature, intended for + uncommon code paths, DWARF exception handling is generally preferred to + SJLJ.
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