gdb: Incorrect stack unwinding if compressed debug info is used

[Vladimir Simonov <sv at sw dot ru>]

Hi all,

Environment: gdb-weekly-CVS-7.2.50.20110125, binutils 2.21, gcc 4.4.3, Linux, i686,
 32 bit kernel 2.6.32.

If I create -Od -g3 executable with -Wl,compressed-debug-sections=zlib
using gold linker or compress debug-info via objcopy I have problems with
local variables and bacttraces in gdb.
Something like this:
gdb: bt
....
#11 0xb2356a74 in Core::WorkerImpl::WorkerThread (this=Could not find
the frame base for "Core::WorkerImpl::WorkerThread()".
)
....

I've spend some time and, looks like, found the problem. It is in
dwarf2_symbol_mark_computed function (dwarf2read.c). Check
"DW_UNSND (attr) < dwarf2_per_objfile->loc.size"
is incorrect if compressed section is used. In this case
loc.size contains compressed section size, not decompressed one.
It happens if the section has not been read via dwarf2_read_section yet.
But dwarf2_locate_sections has been done.
As result symbols not passed above verification are left with
size==0 and data==NULL after dwarf2_symbol_mark_computed function.

The patch idea is to introduce uncompressed_size field in
struct dwarf2_section_info. And fill it in dwarf2_locate_sections.
Check in dwarf2_symbol_mark_computed function takes into
account uncompressed_size. The patch is quite large cause I
try to avoid code duplication with zlib_decompress section.

Any comments are welcome

Best regards
Vladimir Simonov

Attachment: gdb-7.2-compressed-section.diff
Description: Text document