[Dwarf-discuss] Re: optimized code debugging

Jim Blandy jimb
Thu May 26 18:02:24 PDT 2005


There are some central points getting lost here.

The point made in issue 050222.1 is that the compiler may not be able
to tell whether a given address range it's emitting is null or not:
the start and end addresses may be changed by the assembler or linker,
and become equal.  That is, location list entries with identical start
and end addresses may appear without the compiler's knowledge.

Assigning a special interpretation to such entries, as John is
suggesting the standard allow, is just as bad as forbidding them:
either way, you put the compiler in a position where it can't be sure
how the info it's emitting will be interpreted.

Currently, the compiler can't tell if it's producing an error; that's
the problem 050222.1 asks us to fix.  If the standard were to assign a
meaning to null entries, then the compiler wouldn't be able to tell if
it was producing an entry with one the special meanings or not.  But
they're both problems.




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