Date: Tue, 10 Jun 2014 07:38:19 +0100 From: David Chisnall <theraven@FreeBSD.org> To: Ed Maste <emaste@freebsd.org> Cc: freebsd-toolchain@freebsd.org, Ryan Stone <rysto32@gmail.com> Subject: Re: abi::__cxa_demangle provides invalid result on non-mangled symbols Message-ID: <9BDAE8E2-0573-4526-9136-97D3492D7DEF@FreeBSD.org> In-Reply-To: <CAPyFy2Buh4BUEuYW5nfQFdEMio9=yaDAkivg1zXPnEBzr_CzJQ@mail.gmail.com> References: <CAFMmRNw_9hS3YuDbjFJH0btvoPADJ7_4=L13z2sK71gctPzXhQ@mail.gmail.com> <CAPyFy2Buh4BUEuYW5nfQFdEMio9=yaDAkivg1zXPnEBzr_CzJQ@mail.gmail.com>
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On 10 Jun 2014, at 03:44, Ed Maste <emaste@freebsd.org> wrote: > I had the same issue in LLVM, and as hacky as it seems, the solution > is to check that the name starts with "_Z" before passing it to > __cxa_demangle. >=20 > For reference the LLVM review for the change is here: > http://reviews.llvm.org/D2552 >=20 > I didn't get around to testing it on Linux; since you have a test > application ready it would be interesting to see the result of > __cxa_demangle("f") there. If you know that the thing that you are demangling is a symbol name, = then you can use the _Z check, which isn't really a hack - it's a marker = added to identify C++ symbols. Note that, if you're writing portable = code, you need to remember that some systems prepend an underscore to = all compiler-generated symbols, so you may also need to check for __Z = and trim the leading _. The __cxa_demangle() function has to handle things that are not just = symbols (types and so on) and so can't do this test itself. Its most = common use is generating a human-friendly error for an uncaught = exception, where it is just parsing a type encoding. The demangler that we ship is from libelftc. It also fails on a number = of C++11 types and doesn't handle some complex template cases. =20 David
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