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

[Devang Patel]

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