[Lldb-commits] [lldb] r106045 - /lldb/trunk/include/lldb/Core/dwarf.h

[Chris Lattner]

FWIW, I agree with Devang.  It would be nice to have the various dwarf constants all localized.  Imagine a world where the compiler and debugger agree on purpose instead of by accident! :)

-Chris


On Jun 15, 2010, at 11:26 PM, Devang Patel wrote:

> On Tue, Jun 15, 2010 at 8:27 PM, Jason Molenda <jmolenda at apple.com> wrote:
>> 
>> On Jun 15, 2010, at 2:43 PM, Chris Lattner wrote:
>> 
>>> Can Core/dwarf.h use (and extend) llvm/include/llvm/Support/Dwarf.h instead of duplicating much of it?
>> 
>> Yeah, I can do that.  I need to add the full set of DW_OP_{lit,reg,breg}{0..31} constants to include/llvm/Support/Dwarf.h and lib/Support/Dwarf.cpp at the very least.  The printers over in Dwarf.cpp are a little annoying - the DW_TAG ones include the "DW_" prefix, the rest do not.  It always grates one me when I see the prefix missing in program output - I have yet to see a context where the extra three characters would have killed anyone.  I'm adding functions like
>> 
>> const char *
>> DW_ACCESS_value_to_name (uint32_t val)
>> {
>>  static char invalid[100];
>>  const char *llvmstr = AccessibilityString (val);
>>  if (llvmstr == NULL)
>>  {
>>      snprintf (invalid, sizeof (invalid), "Unknown DW_ACCESS constant: 0x%x", val);
>>      return invalid;
>>  }
>> 
>>  std::string str;
>>  if (strlen (llvmstr) < 3 || llvmstr[0] != 'D' || llvmstr[1] != 'W' || llvmstr[2] != '_')
>>    str = "DW_";
>>  str += llvmstr;
>>  ConstString const_str (str.c_str());
>> 
>>  return const_str.GetCString();
>> }
> 
> Instead of doing this, feel free to update llvm/lib/Support/Dwarf.cpp
> printer routines to use DW_ prefix.
> 
>> to lldb's DWARFDefines.cpp to compensate.  We also have a "value to englishy name" utility function that removes all prefix chars (e.g. "DW_FORM_") and changes '_'s to ' ' for printing; they're used in a few places.  To reimplement those on top of the llvm printers I needed to add the modified string to lldb's const string pool and return a pointer to that.  But for the simple value_to_name printers, it's a lot of extra fussing about to ensure that the strings have "DW_" at the front.
>> 
>> 
>> In general I prefer the generated approach used for the header/printer functions in lldb -- there is a text file like
>> 
>> /* START: [7.5.4] Figure 16 "Tag Encodings" (pp. 125-127) in DWARFv3 draft 8 */
>> /* PREFIX: DW_TAG */
>> /* VALIDATTRIBS: DWARFv3 */
>> 
>> array_type 0x01
>> class_type 0x02
>> entry_point 0x03
>> enumeration_type 0x04
>> formal_parameter 0x05
>> imported_declaration 0x08
>> label 0x0a
>> lexical_block 0x0b
>> member 0x0d
>> pointer_type 0x0f
>> 
>> etc. so that only one table is maintained.  A simple script emits the header file and C source file that prints the texts.  In practice the contents change so rarely that it's not a big deal.
>> 
>> 
>> OK to check in the additional constant values to llvm?
> 
> Sure, feel free to add new constants in llvm/include/llvm/Support/Dwarf.h
> 
> -
> Devang