Description
Hello!
I noticed a case where the demangling fails, but where (llvm/apple) c++filt seems to work, with this beauty:
__ZZZN3jkj9dragonbox10to_decimalIfNS0_20default_float_traitsIfEEJNS0_6detail11policy_impl4sign6ignoreENS5_13trailing_zero6removeEEEEDaNS0_23signed_significand_bitsIT_T0_EEjDpT1_ENKUlSC_E_clINS5_26decimal_to_binary_rounding15nearest_to_evenEEESA_SC_ENKUlDpT_E_clIJEEESA_SM_
A self contained test could be
fn main() -> Result<(),std::fmt::Error>{
let mangled = "__ZZZN3jkj9dragonbox10to_decimalIfNS0_20default_float_traitsIfEEJNS0_6detail11policy_impl4sign6ignoreENS5_13trailing_zero6removeEEEEDaNS0_23signed_significand_bitsIT_T0_EEjDpT1_ENKUlSC_E_clINS5_26decimal_to_binary_rounding15nearest_to_evenEEESA_SC_ENKUlDpT_E_clIJEEESA_SM_";
let sym = cpp_demangle::Symbol::new(mangled).unwrap();
let demangled = sym.demangle(&Default::default())?;
println!("Demangled: {}", demangled);
Ok(())
}And that just fails with Error: Error.
c++filt output for me is:
jkj::dragonbox::signed_significand_bits jkj::dragonbox::signed_significand_bits auto jkj::dragonbox::to_decimal<float, jkj::dragonbox::default_float_traits<float>, jkj::dragonbox::detail::policy_impl::sign::ignore, jkj::dragonbox::detail::policy_impl::trailing_zero::remove>(jkj::dragonbox::signed_significand_bits<float, jkj::dragonbox::default_float_traits<float> >, unsigned int, jkj::dragonbox::detail::policy_impl::sign::ignore, jkj::dragonbox::detail::policy_impl::trailing_zero::remove)::'lambda'(jkj::dragonbox::default_float_traits<float>)::operator()<jkj::dragonbox::detail::policy_impl::decimal_to_binary_rounding::nearest_to_even>(jkj::dragonbox::default_float_traits<float>) const::'lambda'(auto...)::operator()<>('lambda'(auto...)) const
And finally attempt to minimise the source of the symbol for proof that I didn't just conjure it up myself. Steps:
git clone https://github.com/jk-jeon/dragonbox.git
vim dragonbox.cpp
clang -std=c++17 -c dragonbox.cpp
nm dragonbox.o | grep __ZZZ
where the dragonbox.cpp contents being:
#include "dragonbox/include/dragonbox/dragonbox.h"
void dragon_test() {
jkj::dragonbox::float_bits<float> br(0.0f);
auto const exponent_bits = br.extract_exponent_bits();
auto const s = br.remove_exponent_bits(exponent_bits);
auto result = jkj::dragonbox::to_decimal(
s, exponent_bits, jkj::dragonbox::policy::sign::ignore,
jkj::dragonbox::policy::trailing_zero::remove);
}
Fiddling with the DemangleOptions didn't seem to affect the outcome.
I wonder if it is possible to make the demangler "fool proof" on valid input, or should there perhaps be some "lossy mode", where it demangles as much as it can, but bails out gracefully giving partial result, for when I don't have too strict needs.