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Tom Tromey 2ddeaf8a7d Handle DW_TAG_variant_part and DW_TAG_variant
This changes dwarf2read to understand DW_TAG_variant_part and
DW_TAG_variant.

Note that DW_AT_discr_list is not handled.  I did not need this for
Rust.  I imagine this should not be too hard to add later, should
someone need it.  Meanwhile I have gdb emit a complaint if it is seen.

There is a lurking issue concerning the placement of the discriminant
in the DWARF.  For Rust, I ended up following the letter of the
standard and having the discriminant be a child of the
DW_TAG_variant_part.  However, GCC's Ada support does not do this.
Pierre-Marie filed this with the DWARF committee:

    http://dwarfstd.org/ShowIssue.php?issue=180123.1

However as that is read-only, if you have comments you might consider
adding them to the GCC bug:

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83935

Finally, there is a DWARF extension lurking in here.  In Rust, a
univariant enum will not have a discriminant.  However, in order to
unify the representation of all data-carrying enums, I've made LLVM
(and my forthcoming rustc patch) emit a univariant enum using a
DW_TAG_variant with a single variant part and without DW_AT_discr.
The lack of this DW_AT_discr is the extension.  I will submit an issue
on dwarfstd.org about this.

2018-02-26  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (struct variant_field): New.
	(struct nextfield) <variant>: New field.
	(dwarf2_add_field): Handle DW_TAG_variant_part.
	(dwarf2_attach_fields_to_type): Attach a discriminant_info to a
	discriminated union.
	(read_structure_type): Handle DW_TAG_variant_part.
	(handle_struct_member_die): New function, extracted from
	process_structure_scope.  Handle DW_TAG_variant.
	(process_structure_scope): Handle discriminated unions.  Call
	handle_struct_member_die.

2018-02-26  Tom Tromey  <tom@tromey.com>

	* gdb.dwarf2/variant.c: New file.
	* gdb.dwarf2/variant.exp: New file.
2018-02-26 09:21:08 -07:00
bfd Segfault on phdrs allocated but not created 2018-02-26 10:51:12 +10:30
binutils BFD messages 2018-02-26 09:33:15 +10:30
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gas GAS/doc: Clean up .dc' and .ds' directive descriptions 2018-02-26 16:11:03 +00:00
gdb Handle DW_TAG_variant_part and DW_TAG_variant 2018-02-26 09:21:08 -07:00
gold New plugin interface to get list of symbols wrapped with --wrap option. 2018-02-22 13:56:46 -08:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
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If you are receiving this as part of a GDB release, see the file gdb/README.
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