[llvm] r263378 - [CodeView] Truncate display names

[David Blaikie via llvm-commits]

On Mon, Mar 14, 2016 at 9:08 AM, David Majnemer <david.majnemer at gmail.com>
wrote:

>
>
> On Sun, Mar 13, 2016 at 12:51 PM, David Blaikie <dblaikie at gmail.com>
> wrote:
>
>>
>>
>> On Sun, Mar 13, 2016 at 3:53 AM, David Majnemer via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: majnemer
>>> Date: Sun Mar 13 05:53:30 2016
>>> New Revision: 263378
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=263378&view=rev
>>> Log:
>>> [CodeView] Truncate display names
>>>
>>> Fundamentally, the length of a variable or function name is bound by the
>>> maximum size of a record: 0xffff.  However, the name doesn't live in a
>>> vacuum; other data is associated with the name, lowering the bound
>>> further.
>>>
>>> We would naively attempt to emit the name, causing us to assert because
>>> the record would no-longer fit in 16-bits.  Instead, truncate the name
>>> but preserve as much as we can.
>>>
>>> While I have tested this locally, I've decided to not commit it due to
>>> the test's size.
>>>
>>
>> ^ Did you change your mind? or unintentionally commit it? (or am I
>> misunderstanding this comment?)
>>
>
> I believe there is a misunderstanding here.  I decided to omit the test
> due to it's size.
>

Oh, I see the other/intended parse for that sentence now. Thanks!


>
>
>>
>>
>>>
>>> N.B.  While this behavior is undesirable, it is better than MSVC's
>>> behavior.  They seem to truncate to ~4000 characters.
>>>
>>> Modified:
>>>     llvm/trunk/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
>>>
>>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp?rev=263378&r1=263377&r2=263378&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp (original)
>>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp Sun Mar 13
>>> 05:53:30 2016
>>> @@ -397,10 +397,11 @@ void CodeViewDebug::emitInlinedCallSite(
>>>    OS.EmitIntValue(SymbolRecordKind::S_INLINESITE_END, 2); // RecordKind
>>>  }
>>>
>>> -static void emitNullTerminatedString(MCStreamer &OS, StringRef S) {
>>> +static void emitNullTerminatedString(MCStreamer &OS, StringRef S,
>>> +                                     size_t MaxSize) {
>>> +  S = S.substr(0, MaxSize);
>>>    SmallString<32> NullTerminatedString(S);
>>> -  if (NullTerminatedString.empty() || NullTerminatedString.back() !=
>>> '\0')
>>> -    NullTerminatedString.push_back('\0');
>>> +  NullTerminatedString.push_back('\0');
>>>    OS.EmitBytes(NullTerminatedString);
>>>  }
>>>
>>> @@ -462,7 +463,8 @@ void CodeViewDebug::emitDebugInfoForFunc
>>>      OS.EmitIntValue(0, 1);
>>>      // Emit the function display name as a null-terminated string.
>>>      OS.AddComment("Function name");
>>> -    emitNullTerminatedString(OS, FuncName);
>>> +    // Truncate the name so we won't overflow the record length field.
>>> +    emitNullTerminatedString(OS, FuncName, 0xffd9);
>>>      OS.EmitLabel(ProcRecordEnd);
>>>
>>>      for (const LocalVariable &Var : FI.Locals)
>>> @@ -706,7 +708,8 @@ void CodeViewDebug::emitLocalVariable(co
>>>    OS.EmitIntValue(TypeIndex::Int32().getIndex(), 4);
>>>    OS.AddComment("Flags");
>>>    OS.EmitIntValue(Flags, 2);
>>> -  emitNullTerminatedString(OS, Var.DIVar->getName());
>>> +  // Truncate the name so we won't overflow the record length field.
>>> +  emitNullTerminatedString(OS, Var.DIVar->getName(), 0xfff6);
>>>    OS.EmitLabel(LocalEnd);
>>>
>>>    // Calculate the on disk prefix of the appropriate def range record.
>>> The
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>
>>
>>
>
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