[Dwarf-Discuss] Inconsistency in DWARF length escape codes

[Ron Brender]

What was the resolution of this question? I agree that it is merely a 
typo. I note that

   - there is  one  occurrence  of 0xfffffff0
   - there are four occurrences of 0xffffff00

This suggests that the typo is in the first case (0xfffffff0 should be 
0xffffff00).

Shall I go ahead and make that correction? Or does someone want to 
debate whether we need 16 vs 256 escape codes? (IMHO 16 is undoubtedly 
enough, but it is outvoted 4 to 1. :-)

FWIW, in searching my archives I was unable to find the original 
proposal we adopted that established the escape scheme way back when...

Ron

--------------------
Michael Eager wrote:
> Nick Clifton wrote:
>> Hi Guys,
>>
>>    There appears to be an inconsistency in the DWARF3 specification for the 
>> range of values that can be used as escape codes in the initial 4-byte length 
>> field of some headers:
>>
>>    In section 7.2.2 (Initial Length Values) on page 120 of the DWARF3 spec 
>> (published Dec 20, 2005 and downloaded from http://dwarfstd.org) it says:
>>
>>      "In an initial length field, the values 0xfffffff0 through
>>       0xffffffff are reserved by DWARF to indicate some form of
>>       extension relative to DWARF Version 2; such values must
>>       not be interpreted as a length field."
>>
>> Note that the start value has seven 'f's and only one 0.  On the next page 
>> however (Section 7.4 32-Bit and 64-Bit DWARF Formats) in item 1 it says:
>>
>>      "In the 32-bit DWARF format, an initial length field (see
>>       Section 7.2.2) is an unsigned 32-bit integer (which must
>>       be less than 0xffffff00);"
>>
>> This time the reserved value has six 'f's and two 0's.  This smaller value is 
>> also referred to in Section 7.5.1, Section 7.19 and Section 7.20.
>>
>> It would appear that Section 7.2.2 contains a typo and that the lower reserved 
>> value ought to be 0xffffff00.   On the other hand is there really a need for 
>> 256 escape codes ?  Maybe the other sections are wrong and their lower limits 
>> should be changed to 0xfffffff0 ?
>>
>> What do you think ?
> 
> I think that you found a typo.  The values should all be the same.
> (It also points out that the DWARF standard should have only one place
> where each value is defined.)
> 
> I don't recall the rationale for the range of reserved values.  But
> I think that your question about whether 16 reserved values are adequate
> is reasonable.  I don't see a need for more.
>