[Bug gdb/27962] New: Internal error when using binary from gdb.dwarf2/arr-stride.exp

[Bug gdb/27962] New: Internal error when using binary from gdb.dwarf2/arr-stride.exp

[simark at simark dot ca]

https://sourceware.org/bugzilla/show_bug.cgi?id=27962

            Bug ID: 27962
           Summary: Internal error when using binary from
                    gdb.dwarf2/arr-stride.exp
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: simark at simark dot ca
  Target Milestone: ---

I stumbled on this a bit randomly while trying to reproduce a failure.  With
the binary from gdb.dwarf2/arr-stride.exp, with current master:

$ ./gdb -nx -q --data-directory=data-directory
testsuite/outputs/gdb.dwarf2/arr-stride/arr-stride  -ex "print the_struct"
Reading symbols from testsuite/outputs/gdb.dwarf2/arr-stride/arr-stride...
$1 = {intfield = 1, arrayfield = {
/home/simark/src/binutils-gdb/gdb/value.c:851: internal-error: bool
value_contents_bits_eq(const value*, int, const value*, int, int): Assertion
`offset2 + length <= TYPE_LENGTH (val2->enclosing_type) * TARGET_CHAR_BIT'
failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) 



(top-gdb) p offset2
$1 = 32
(top-gdb) p length
$2 = 32
(top-gdb) p TYPE_LENGTH (val2->enclosing_type)
$3 = 4
(top-gdb) p TARGET_CHAR_BIT
$4 = 8

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[Bug gdb/27962] Internal error when using binary from gdb.dwarf2/arr-stride.exp

[simark at simark dot ca]

https://sourceware.org/bugzilla/show_bug.cgi?id=27962

--- Comment #1 from Simon Marchi <simark at simark dot ca> ---
If I use `-ex "set language ada"` before the print, as the test does, I don't
hit an internal error.

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[Bug gdb/27962] Internal error when using binary from gdb.dwarf2/arr-stride.exp

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27962

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
At first I thought this was because we're trying to print
an optimized-out array.  And, that still seems weird, maybe
common_val_print and common_val_print_checked should be merged

However, it's also the case that this array has a bit stride of 6.
So, this may just be a missing feature in value_print_array_elements.

I'm not sure how important this is.  Arrays like this can't be
created in most languages that gdb supports.  OTOH, it should be
safe to print a value, regardless of the current language.

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[Bug gdb/27962] Internal error when using binary from gdb.dwarf2/arr-stride.exp

[simark at simark dot ca]

https://sourceware.org/bugzilla/show_bug.cgi?id=27962

--- Comment #3 from Simon Marchi <simark at simark dot ca> ---
I don't have enough context nor time to dig into it.  But yeah, any way to
trigger an internal error can be considered a bug.  So if there's just no sane
way of printing the value for languages other than Ada, then at least erroring
out would be better than an internal error.

But why is it needed to set the language explicitly, given that the CU
provides:

  DW_AT_language @DW_LANG_Ada95

?

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[Bug gdb/27962] Internal error when using binary from gdb.dwarf2/arr-stride.exp

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27962

--- Comment #4 from Tom Tromey <tromey at sourceware dot org> ---
(In reply to Simon Marchi from comment #3)

> But why is it needed to set the language explicitly, given that the CU
> provides:
> 
>   DW_AT_language @DW_LANG_Ada95
> 
> ?

The program's "main" isn't given a language.

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