[clang] [llvm] [clang][LLVM Demangler] Add an assertion that validates that all mang… (PR #111391)

[Viktoriia Bakalova via cfe-commits]

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@@ -1967,6 +1967,10 @@ def fclang_abi_compat_EQ : Joined<["-"], "fclang-abi-compat=">, Group<f_clang_Gr
   Visibility<[ClangOption, CC1Option]>,
   MetaVarName<"<version>">, Values<"<major>.<minor>,latest">,
   HelpText<"Attempt to match the ABI of Clang <version>">;
+def fno_demangling_failures: Flag<["-"], "fno-demangling-failures">, Group<f_clang_Group>,
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VitaNuo wrote:

Yeah this flag turns on an assertion that validates that all the manglings produced by clang can be demangled. In this sense it on & off (off by default). Let me know if I misunderstand something. 

https://github.com/llvm/llvm-project/pull/111391