Dodji Seketeli 160961f3cb Bug 18818 - abidw aborts on a class with a non-complete base class ...

On some binaries with debug info emitted by "Ubuntu clang version
3.6.0-2ubuntu1" and "GNU C++ 4.9.2" (as the value of the
DW_AT_producer property), it seems some classes can have a base class
that is not complete.  E.g, the debug info (that I have extracted
using the command eu-readelf --debug-dump=info
<the-binary-attached-to-the-bug>) has these relevant pieces:

    [...]

     [  5ff7]        class_type
		     containing_type      (ref4) [  7485]
		     name                 (strp) "system_error"
		     byte_size            (data1) 40
		     decl_file            (data1) 46
		     decl_line            (data1) 22
     [  6003]          inheritance
		       type                 (ref4) [  7480]
    [...]

Here, we are looking at the type system_error (actually
boost::system::system_error) that inherits the type which DIE is
referred to as offset '7480'.

Then the definition of the DIE at offset 7480 is:

    [...]

     [  7480]      class_type
		   name                 (strp) "runtime_error"
		   declaration          (flag_present)
     [  7485]      class_type
		   name                 (strp) "exception"
		   declaration          (flag_present)
    [...]

You can see that the type "runtime_error" (actually
std::runtime_error) has the flag DW_AT_declaration set, marking it as
a declaration (with no definition yet).  And no other DIE in the same
translation unit
(src/third_party/boost-1.56.0/libs/filesystem/src/codecvt_error_category.cpp)
or in the same DSO provides the definition for that declaration.

I believe this is ill-formed.  A base class should be defined and have
a layout completed expressed and accessible from the translation unit
it's used in.

The patch I am proposing detects that the base class is still
incomplete when we finish loading the current binary.  In that case,
the base class is made complete with a size of 1.  Meaning it's an
empty class (with no data member and no base class).  This works as a
viable work-around *if* the producer only omitted definitions for
empty classes.  We'll need to fix the producers eventually.

	* src/abg-dwarf-reader.cc
	(read_context::decl_only_classes_to_force_defined_map_): New data
	member.
	(read_context::declaration_only_classes_to_force_defined): New
	accessors.
	(read_context::schedule_declaration_only_class_for_forced_resolution):
	New member function.
	(build_class_type_and_add_to_ir): If a base class is a
	declaration-only class then mark it as needing to be force-defined
	*if* it's still not defined at the end of the abi corpus loading.
	(read_context::resolve_declaration_only_classes): If
	declaration-only classes that need to force-defined are present
	and not defined (when we reach the end of the ABI corpus) then
	force-define them as empty classes.
	* tests/data/test-read-dwarf/test10-pr18818-gcc.so: New test
	binary input file.  This comes from a user binary submitted to bug
	https://sourceware.org/bugzilla/show_bug.cgi?id=18818.  The
	original URL to the binary is
	https://sourceware.org/bugzilla/attachment.cgi?id=8518.
	* tests/data/test-read-dwarf/test9-pr18818-clang.so: New binary
	input file.  This comes from the same bug report as above.  The
	original URL to the binary is
	https://sourceware.org/bugzilla/attachment.cgi?id=8511.
	* tests/data/test-read-dwarf/test10-pr18818-gcc.so.abi: New
	reference output file.
	* tests/data/test-read-dwarf/test9-pr18818-clang.so.abi: Likewise.
	* tests/data/Makefile.am: Add the new files above to the source
	distribution.
	* tests/test-read-dwarf.cc (in_out_specs): Add the test inputs
	above the set of tests input this harness has to run over.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>

2015-08-14 16:22:14 +02:00

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