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

[Reid Kleckner]

OTOH a disassembler is not a compiler.  It's just a debugging aid.  While
it's conceptually nice that llvm-c-test --disassemble produces the same
outputs on all platforms, it's not as important as being able to do perfect
cross compilation.

Is there a way to structure this so that the symbolization is delegated to
the user of the C API, or is that too disruptive?


On Fri, Jan 3, 2014 at 3:37 PM, David Majnemer <david.majnemer at gmail.com>wrote:

> 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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