[llvm] r198441 - For disassembly when adding a symbolic operand that is a C++

[David Majnemer]

Unless I am mistaken, the correct thing to do would be to provide an
implementation of symbol demangling within LLVM itself.
This way we could demangle Itanium-style symbols without relying on
::abi::__cxa_demangle and MSVC-style symbols without relying on
::UnDecorateSymbolName.

Relying on the host's ABI details to help disassemble code for a target
seems like the wrong approach.


On Fri, Jan 3, 2014 at 12:06 PM, Howard Hinnant <hhinnant at apple.com> wrote:

> abi::__cxa_demangle and <cxxabi.h> are part of the Itanium ABI.  MS
> doesn't support this unofficial standard.  Sorry, I don't know how to
> demangle names on Windows.  I believe that their type_info.name() returns
> an demangled name.  But I don't know that this info helps.
>
> Howard
>
> On Jan 3, 2014, at 3:02 PM, Kevin Enderby <enderby at apple.com> wrote:
>
> > Hi Reid,
> >
> > Sorry about that.  I'll revert my change.
> >
> > Not sure the best way to get this done if an ifdef is not acceptable.
>  Maybe Howard or others will have better suggestions.
> >
> > It does not have any tests as this is used by darwin's otool(1) that
> links with the llvm disassembler.  We have had this problem with this part
> of the disassembler since day one.  So I'm not sure the best way to address
> that either.
> >
> > Kev
> >
> > On Jan 3, 2014, at 11:54 AM, Reid Kleckner <rnk at google.com> wrote:
> >
> >> Microsoft doesn't ship a <cxxabi.h> header:
> >>
> http://lab.llvm.org:8011/builders/lld-x86_64-win7/builds/5504/steps/build_Lld/logs/stdio
> >> MCExternalSymbolizer.cpp(16): fatal error C1083: Cannot open include
> file: 'cxxabi.h': No such file or directory
> >>
> >> I'm not familiar with this code, but it seems bad to make the result of
> LLVMDisasmInstruction dependent on the target platform, so throwing this
> behind a quick ifdef isn't necessarily right either.
> >>
> >> This also doesn't have any tests.
> >>
> >>
> >> On Fri, Jan 3, 2014 at 11:33 AM, Kevin Enderby <enderby at apple.com>
> wrote:
> >> Author: enderby
> >> Date: Fri Jan  3 13:33:09 2014
> >> New Revision: 198441
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=198441&view=rev
> >> Log:
> >> For disassembly when adding a symbolic operand that is a C++
> >> symbol name, also put the human readable name in a comment.
> >>
> >> Also fix a bug in LLVMDisasmInstruction() that was not flushing
> >> the raw_svector_ostream for the disassembled instruction string
> >> before copying it to the output buffer that was causing truncation
> >> of the output.
> >>
> >> rdar://10173828
> >>
> >> Modified:
> >>     llvm/trunk/lib/MC/MCDisassembler/Disassembler.cpp
> >>     llvm/trunk/lib/MC/MCExternalSymbolizer.cpp
> >>
> >> Modified: llvm/trunk/lib/MC/MCDisassembler/Disassembler.cpp
> >> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCDisassembler/Disassembler.cpp?rev=198441&r1=198440&r2=198441&view=diff
> >>
> ==============================================================================
> >> --- llvm/trunk/lib/MC/MCDisassembler/Disassembler.cpp (original)
> >> +++ llvm/trunk/lib/MC/MCDisassembler/Disassembler.cpp Fri Jan  3
> 13:33:09 2014
> >> @@ -298,6 +298,7 @@ size_t LLVMDisasmInstruction(LLVMDisasmC
> >>        emitLatency(DC, Inst);
> >>
> >>      emitComments(DC, FormattedOS);
> >> +    OS.flush();
> >>
> >>      assert(OutStringSize != 0 && "Output buffer cannot be zero size");
> >>      size_t OutputSize = std::min(OutStringSize-1, InsnStr.size());
> >>
> >> Modified: llvm/trunk/lib/MC/MCExternalSymbolizer.cpp
> >> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCExternalSymbolizer.cpp?rev=198441&r1=198440&r2=198441&view=diff
> >>
> ==============================================================================
> >> --- llvm/trunk/lib/MC/MCExternalSymbolizer.cpp (original)
> >> +++ llvm/trunk/lib/MC/MCExternalSymbolizer.cpp Fri Jan  3 13:33:09 2014
> >> @@ -13,6 +13,7 @@
> >>  #include "llvm/MC/MCInst.h"
> >>  #include "llvm/Support/raw_ostream.h"
> >>  #include <cstring>
> >> +#include <cxxabi.h>
> >>
> >>  using namespace llvm;
> >>
> >> @@ -56,6 +57,14 @@ bool MCExternalSymbolizer::tryAddingSymb
> >>      if (Name) {
> >>        SymbolicOp.AddSymbol.Name = Name;
> >>        SymbolicOp.AddSymbol.Present = true;
> >> +      // If Name is a C++ symbol name put the human readable name in a
> comment.
> >> +      if (strncmp(Name, "__Z", 3) == 0) {
> >> +        char *demangled = abi::__cxa_demangle(Name + 1, 0, 0, 0);
> >> +       if (demangled) {
> >> +          cStream << demangled;
> >> +          free(demangled);
> >> +        }
> >> +      }
> >>      }
> >>      // For branches always create an MCExpr so it gets printed as hex
> address.
> >>      else if (IsBranch) {
> >>
> >>
> >> _______________________________________________
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> >>
> >
>
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