[patch] Allow dummy CUs created by incremental linker

[Cary Coutant <ccoutant at google dot com>]

With the new incremental linking support in gold, we leave patch space
in the file at link time, and use that patch space for incremental
updates. If the file has debug info, that means that the debug info
might have "holes" in it. Because the debugger can't deal with
arbitrary holes in the debug info, gold fills the holes with dummy
compilation units, where each dummy CU consists of a compilation unit
header whose length field cover the hole, and the rest of the space
filled with zeroes. This patch updated gdb to tolerate these dummy
CUs, by checking for an empty CU before attempting to read the DIEs.

Tested on x86_64 with the latest gold.

-cary


	* dwarf2read.c (peek_abbrev_code): New function.
	(dw2_get_file_names): Check for dummy compilation units.
	(create_debug_types_hash_table): Likewise.
	(process_psymtab_comp_unit): Likewise.
	(load_partial_comp_unit): Likewise.
	(load_full_comp_unit): Likewise.

Attachment: gdb-empty-cu-patch-2.txt
Description: Text document