The .gdb_index was designed such that all data would be aligned.
Unfortunately, we neglected to require this alignment in the objcopy
instructions in the manual. As a result, in many cases, a .gdb_index
in the wild will not be properly aligned by mmap. This yields
undefined behavior, which is PR gdb/23743.
This patch fixes the bug by always assuming that the mapping is
unaligned, and using extract_unsigned_integer when needed. A new
helper class is introduced to make this less painful.
gdb/ChangeLog
2021-04-17 Tom Tromey <tom@tromey.com>