Tom de Vries ad14ab00eb [gdb/symtab] Fix unhandled dwarf expression opcode with gcc-11 -gdwarf-5
[ I've confused things by forgetting to add -gdwarf-4 in $subject of
commit 0057a7ee0d9 "[gdb/testsuite] Add KFAILs for gdb.ada FAILs with
gcc-11".  So I'm adding here -gdwarf-5 in $subject, even though -gdwarf-5 is
the default for gcc-11.  I keep getting confused because of working with a
system gcc-11 compiler that was patched to switch the default back to
-gdwarf-4. ]

When running test-case gdb.ada/arrayptr.exp with gcc-11 (and default
-gdwarf-5), I run into:
...
(gdb) print pa_ptr.all^M
Unhandled dwarf expression opcode 0xff^M
(gdb) FAIL: gdb.ada/arrayptr.exp: scenario=all: print pa_ptr.all
...

What happens is that pa_ptr:
...
 <2><1523>: Abbrev Number: 3 (DW_TAG_variable)
    <1524>   DW_AT_name        : pa_ptr
    <1529>   DW_AT_type        : <0x14fa>
...
has type:
...
 <2><14fa>: Abbrev Number: 2 (DW_TAG_typedef)
    <14fb>   DW_AT_name        : foo__packed_array_ptr
    <1500>   DW_AT_type        : <0x1504>
 <2><1504>: Abbrev Number: 4 (DW_TAG_pointer_type)
    <1505>   DW_AT_byte_size   : 8
    <1505>   DW_AT_type        : <0x1509>
...
which is a pointer to a subrange:
...
 <2><1509>: Abbrev Number: 12 (DW_TAG_subrange_type)
    <150a>   DW_AT_lower_bound : 0
    <150b>   DW_AT_upper_bound : 0x3fffffffffffffffff
    <151b>   DW_AT_name        : foo__packed_array
    <151f>   DW_AT_type        : <0x15cc>
    <1523>   DW_AT_artificial  : 1
 <1><15cc>: Abbrev Number: 5 (DW_TAG_base_type)
    <15cd>   DW_AT_byte_size   : 16
    <15ce>   DW_AT_encoding    : 7      (unsigned)
    <15cf>   DW_AT_name        : long_long_long_unsigned
    <15d3>   DW_AT_artificial  : 1
...
with upper bound of form DW_FORM_data16.

In gdb/dwarf/attribute.h we have:
...
  /* Return non-zero if ATTR's value falls in the 'constant' class, or
     zero otherwise.  When this function returns true, you can apply
     the constant_value method to it.
     ...
     DW_FORM_data16 is not considered as constant_value cannot handle
     that.  */
  bool form_is_constant () const;
...
so instead we have attribute::form_is_block (DW_FORM_data16) == true.

Then in attr_to_dynamic_prop for the upper bound, we get a PROC_LOCEXPR
instead of a PROP_CONST and end up trying to evaluate the constant
0x3fffffffffffffffff as if it were a locexpr, which causes the
"Unhandled dwarf expression opcode 0xff".

In contrast, with -gdwarf-4 we have:
...
    <164c>   DW_AT_upper_bound : 18 byte block: \
      9e 10 ff ff ff ff ff ff ff ff 3f 0 0 0 0 0 0 0 \
      (DW_OP_implicit_value 16 byte block: \
        ff ff ff ff ff ff ff ff 3f 0 0 0 0 0 0 0 )
...

Fix the dwarf error by translating the DW_FORM_data16 constant into a
PROC_LOCEXPR, effectively by prepending 0x9e 0x10, such that we have same
result as with -gdwarf-4:
...
(gdb) print pa_ptr.all^M
That operation is not available on integers of more than 8 bytes.^M
(gdb) KFAIL: gdb.ada/arrayptr.exp: scenario=all: print pa_ptr.all \
  (PRMS: gdb/20991)
...

Tested on x86_64-linux, with gcc-11 and target board
unix/gdb:debug_flags=-gdwarf-5.

gdb/ChangeLog:

2021-07-25  Tom de Vries  <tdevries@suse.de>

	* dwarf2/read.c (attr_to_dynamic_prop): Handle DW_FORM_data16.
2021-07-28 10:01:05 +02:00
2021-07-21 11:00:35 +09:30
2021-07-03 14:50:57 +01:00
2020-09-25 10:24:44 -04:00
2021-07-03 14:50:57 +01:00
2021-07-26 07:34:37 -06:00
2021-07-03 14:50:57 +01:00
2021-07-03 14:50:57 +01:00
2021-05-29 11:56:43 -04:00
2021-05-29 11:56:43 -04:00
2021-05-18 17:47:27 -04:00
2021-05-18 17:47:27 -04:00
2021-01-12 18:19:20 -05:00

		   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.
Description
Unofficial mirror of sourceware binutils-gdb repository. Updated daily.
Readme 780 MiB
Languages
C 51.8%
Makefile 22.4%
Assembly 12.3%
C++ 6%
Roff 1.4%
Other 5.4%