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ad14ab00eb
[ 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.
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