https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101643
Bug ID: 101643
Summary: [debug, ada] packed array not described as packed
Product: gcc
Version: 7.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
[ Filing FTR. ]
Consider gdb test-case foo_ra24_010.adb / pck.adb / pck.ads (
https://sourceware.org/git/?p=binutils-gdb.git;a=tree;f=gdb/testsuite/gdb.ada/big_packed_array
).
With gcc-8.5.0 we have:
...
$ gnatmake-8 -f foo_ra24_010.adb -fgnat-encodings=minimal -g
$ gdb -q -batch ./foo_ra24_010 -ex start -ex n -ex n -ex 'p bad'
Temporary breakpoint 1 at 0x402ce6: file foo_ra24_010.adb, line 19.
Temporary breakpoint 1, foo_ra24_010 () at foo_ra24_010.adb:19
19 Good : PA := (others => False);
20 Bad : Bad_Packed_Table := (others => False);
22 Do_Nothing (Good'Address); -- STOP
$1 = (0 => 0 <repeats 25 times>)
...
while with gcc-9.3.1 we have:
...
$ gnatmake-9 -f foo_ra24_010.adb -fgnat-encodings=minimal -g
+ gdb -q -batch ./foo_ra24_010 -ex start -ex n -ex n -ex 'p bad'
Temporary breakpoint 1 at 0x402d24: file foo_ra24_010.adb, line 19.
Temporary breakpoint 1, foo_ra24_010 () at foo_ra24_010.adb:19
19 Good : PA := (others => False);
20 Bad : Bad_Packed_Table := (others => False);
22 Do_Nothing (Good'Address); -- STOP
$1 = (false <repeats 196 times>)
...
The difference in gdb behaviour is caused by the dwarf information.
With gcc-8.5.0 we have:
...
<2><2074>: Abbrev Number: 10 (DW_TAG_variable)
<2075> DW_AT_name : bad
<207c> DW_AT_type : <0x2028>
<1><2028>: Abbrev Number: 5 (DW_TAG_array_type)
<2029> DW_AT_name : pck__t
<202d> DW_AT_bit_stride : 8
<202e> DW_AT_type : <0x2003>
<2032> DW_AT_alignment : 1
<2033> DW_AT_sibling : <0x203f>
<2><2037>: Abbrev Number: 7 (DW_TAG_subrange_type)
<2038> DW_AT_type : <0x200a>
<203c> DW_AT_lower_bound : 0
<203d> DW_AT_upper_bound : 24
<2><203e>: Abbrev Number: 0
<1><2003>: Abbrev Number: 4 (DW_TAG_base_type)
<2004> DW_AT_byte_size : 1
<2005> DW_AT_encoding : 7 (unsigned)
<2006> DW_AT_name : system__unsigned_types__packed_byte
<1><200a>: Abbrev Number: 4 (DW_TAG_base_type)
<200b> DW_AT_byte_size : 4
<200c> DW_AT_encoding : 5 (signed)
<200d> DW_AT_name : integer
...
With gcc-9.3.1 we have for foo_ra24_010.adb:
...
<2><20a1>: Abbrev Number: 11 (DW_TAG_variable)
<20a2> DW_AT_name : bad
<20a9> DW_AT_type : <0x205f>
<1><205f>: Abbrev Number: 7 (DW_TAG_typedef)
<2060> DW_AT_name : pck__bad_packed_table
<2067> DW_AT_type : <0x2048>
<206b> DW_AT_alignment : 1
<1><2048>: Abbrev Number: 5 (DW_TAG_array_type)
<2049> DW_AT_name : pck__t___XP1
<204d> DW_AT_bit_stride : 8
<204e> DW_AT_type : <0x2016>
<2052> DW_AT_alignment : 1
<2><2057>: Abbrev Number: 8 (DW_TAG_subrange_type)
<2058> DW_AT_type : <0x201d>
<205c> DW_AT_lower_bound : 0
<205d> DW_AT_upper_bound : 24
<2><205e>: Abbrev Number: 0
<1><2016>: Abbrev Number: 4 (DW_TAG_base_type)
<2017> DW_AT_byte_size : 1
<2018> DW_AT_encoding : 7 (unsigned)
<2019> DW_AT_name : system__unsigned_types__packed_byte
<1><201d>: Abbrev Number: 4 (DW_TAG_base_type)
<201e> DW_AT_byte_size : 4
<201f> DW_AT_encoding : 5 (signed)
<2020> DW_AT_name : integer
...
and with pck__t___XP1 listed once more for pck.adb as:
...
<1><1ab5>: Abbrev Number: 5 (DW_TAG_array_type)
<1ab6> DW_AT_name : pck__t___XP1
<1aba> DW_AT_bit_stride : 1
<1abb> DW_AT_type : <0x1aa0>
<1abf> DW_AT_alignment : 1
<2><1ac4>: Abbrev Number: 6 (DW_TAG_subrange_type)
<1ac5> DW_AT_type : <0x15f9>
<1ac9> DW_AT_lower_bound : 0
<1aca> DW_AT_upper_bound : 195
<2><1acb>: Abbrev Number: 0
<1><1aa0>: Abbrev Number: 4 (DW_TAG_base_type)
<1aa1> DW_AT_byte_size : 1
<1aa2> DW_AT_encoding : 2 (boolean)
<1aa3> DW_AT_name : boolean
<1><15f9>: Abbrev Number: 2 (DW_TAG_enumeration_type)
<15fa> DW_AT_name : pck__enum_idx
<15fe> DW_AT_encoding : 7 (unsigned)
<15ff> DW_AT_byte_size : 1
...
ISTM that in the gcc-8.5.0 case, gdb does the best it can do with the info
provided, and that is this a gcc bug.
