Hi,

I've been chasing failures on gdb.cp/nsalias.exp for MIPS, but the 
strange thing is that the failures only reproduced with a GDB built 
without optimization.

Upon further investigation, i noticed the testcase was generating 
DW_AT_high_pc and DW_AT_low_pc entries with type DW_FORM_string, which 
is wrong.

GDB was using that information to load data as strings, and then 
proceeded to use the string pointers as addresses.

Even then, the test was passing just fine, because we were lucky enough 
to have the low_pc string pointer smaller than the high_pc string pointer.

The following patch fixes two issues. The first one is the 
DW_FORM_string type. The second one is adjusting the addresses so that 
they are non-zero, since GDB doesn't like seeing 0 in these fields due 
to a check contained in dwarf2_get_pc_bounds:

   if (low == 0 && !dwarf2_per_objfile->has_section_at_zero)
     return 0;

With both fixes, the testcase passes deterministically, and the failures 
i saw for the MIPS case were bad luck with the pointer comparisons.

OK?