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Kevin Buettner a6b786da4e Add support for DW_OP_GNU_variable_value
This patch adds support for DW_OP_GNU_variable_value to GDB.

Jakub Jelinek provides a fairly expansive discussion of this DWARF
expression opcode in his GCC patch...

    https://gcc.gnu.org/ml/gcc-patches/2017-02/msg01499.html

It has also been proposed for addition to the DWARF Standard:

    http://www.dwarfstd.org/ShowIssue.php?issue=161109.2

If compiled with a suitable version of GCC, the test case associated
with GCC Bug 77589 uses DW_OP_GNU_variable_value in a DW_AT_byte_stride
expression.  Here's a link to the bug:

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77589

This is what the DWARF looks like.  Look at the last line, which has
the DW_AT_byte_stride expression:

 <2><e1>: Abbrev Number: 12 (DW_TAG_variable)
    <e2>   DW_AT_name        : (indirect string, offset: 0x115): span.0
    <e6>   DW_AT_type        : <0x2e>
    <ea>   DW_AT_artificial  : 1
    <ea>   DW_AT_location    : 3 byte block: 91 b0 7f 	(DW_OP_fbreg: -80)
 ...
 <2><178>: Abbrev Number: 18 (DW_TAG_subrange_type)
    <179>   DW_AT_lower_bound : 4 byte block: 97 23 20 6 	(DW_OP_push_object_address; DW_OP_plus_uconst: 32; DW_OP_deref)
    <17e>   DW_AT_upper_bound : 4 byte block: 97 23 28 6 	(DW_OP_push_object_address; DW_OP_plus_uconst: 40; DW_OP_deref)
    <183>   DW_AT_byte_stride : 10 byte block: 97 23 18 6 fd e1 0 0 0 1e 	(DW_OP_push_object_address; DW_OP_plus_uconst: 24; DW_OP_deref; DW_OP_GNU_variable_value: <0xe1>; DW_OP_mul)

A patch to readelf, which I'm also submitting, is required to do this
decoding.

I found that GDB gave me the correct answer for "p c40pt(2)" once I
(correctly) implemented DW_OP_GNU_variable_value.

I also have test case (later in this series) which uses the DWARF
assembler and, therefore, do not rely on having a compiler with this
support.

gdb/ChangeLog:

	* dwarf2expr.h (struct dwarf_expr_context): Add virtual method
	dwarf_variable_value.
	* dwarf2-frame.c (class dwarf_expr_executor):
	Add override for dwarf_variable_value.
	* dwarf2loc.c (class dwarf_evaluate_loc_desc): Likewise.
	(class symbol_needs_eval_context): Likewise.
	(indirect_synthetic_pointer): Add forward declaration.
	(sect_variable_value): New function.
	(dwarf2_compile_expr_to_ax): Add case for DW_OP_GNU_variable_value.
	* dwarf2expr.c (dwarf_expr_context::execute_stack_op): Add case
	for DW_OP_GNU_variable_value.
2018-08-18 12:57:59 -07:00
bfd Automatic date update in version.in 2018-08-18 00:00:26 +00:00
binutils binutils testsuite strip-13 test 2018-08-18 13:46:32 +09:30
config
contrib Update dg-extract-results.* from gcc 2018-08-06 16:05:16 +02:00
cpu
elfcpp
etc
gas Opcodes: (BRCLR / BRSET) Disassemble reserved codes instead of aborting. 2018-08-18 07:50:57 +02:00
gdb Add support for DW_OP_GNU_variable_value 2018-08-18 12:57:59 -07:00
gold Fix "may be used uninitialized" warning. 2018-08-07 22:40:33 -07:00
gprof
include S12Z: Move opcode header to public include directory. 2018-08-18 07:50:03 +02:00
intl Backport gettext fixes to get rid of warnings on macOS 2018-08-02 14:56:02 -04:00
ld Remove duplicate ld testsuite function 2018-08-18 13:47:03 +09:30
libdecnumber
libiberty Copy from GCC: Add linker_output as prefix for LTO temps (PR lto/86548). 2018-08-01 14:23:10 +01:00
opcodes Opcodes: (BRCLR / BRSET) Disassemble reserved codes instead of aborting. 2018-08-18 07:50:57 +02:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.

REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.