On Tue, 2005-08-09 at 12:28 +0100, Daniel Towner wrote: > Hi all, > > I am encountering a problem with DWARF location lists. Consider the > following assembly: > > _Ltext: > main: > _LVL0: > ;# basic block 0 > _LVL1: > > This generates a DWARF location list entry whose begin and end addresses > are identical, due to the empty basic block. Not a great problem on the > face of it, but I'm using gcc in an embedded system in which the `main' > function is placed at address 0. > Thus, the location list entry gets an > address range of [0, 0) which denotes the supposed end of the location > list. This corrupts the location list, making it impossible to debug > optimised code.
> Would it be difficult to detect empty location list so that they are > never emitted? It depends. We already try to elide obviously empty ones when possible. NOTES get in the way sometimes, and we don't try to handle that (see dwarf2out.c:add_var_loc_to_decl) However, even if you did handle that, you couldn't remove all of the empty location lists because the code between them may disappear in machine reorg, linker relaxation, etc.
