On 1/25/21 7:12 PM, Simon Marchi wrote:
> 
> 
> On 2021-01-25 12:42 p.m., Bernd Edlinger wrote:
>> On 1/25/21 5:36 PM, Simon Marchi wrote:
>>>> Yes, unfortunately I have not any experience with writing such assembly
>>>> tests, but I am always impressed when one of you does it though :-)
>>>>
>>>> Nevertheless, the test case seems to be stable from gcc-4.8 .. gcc-11,
>>>> that it fails without the patch and passes with the patch.
>>>>
>>>> So is it okay to push my partial symbols test as-is?
>>>
>>> My patch here adds a test that uses DW_FORM_sec_offset to point
>>> to a .debug_rnglists (DWARF5) section.  Maybe that's sufficient,
>>> but if not I could probably do a DWARF4 equivalent.
>>>
>>>   https://sourceware.org/pipermail/gdb-patches/2021-January/175229.html
>>>
>>
>> Yeah, the hardest part on a one-line change like this is always the test case.
>>
>> So, I tried this patch on current trunk, but it fails:
>>
>> Running /home/ed/gnu/gdb-build-1/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.dwarf2/rnglists-multiple-cus.exp ...
>> ERROR: Couldn't load rnglists-multiple-cus-dw32 into GDB (GDB internal error).
>> ERROR: Couldn't load rnglists-multiple-cus-dw64 into GDB (GDB internal error).
>> Running /home/ed/gnu/gdb-build-1/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.dwarf2/rnglists-sec-offset.exp ...
>> FAIL: gdb.dwarf2/rnglists-sec-offset.exp: is_64=false: p/x &foo
>> FAIL: gdb.dwarf2/rnglists-sec-offset.exp: is_64=true: p/x &foo
>>
>> This probably means that your test tests more than this single-line change alone?
> 
> Hmm, with current master (so with Tom's patch merged),
> gdb.dwarf2/rnglists-sec-offset.exp passes for me.
> 

That will probably need investigation.
Let's first check if I applied the corrrect test case,
see attached patch.txt.

tried to do "readelf --debug-dump rnglists-sec-offset-dw32" and
"readelf --debug-dump rnglists-sec-offset-dw64"

I used GNU readelf (GNU Binutils) 2.35.1

I see a warning:
readelf: Warnung: The .debug_rnglists section contains unsupported offset entry count: 2.


what does that mean?
Doesn't that indicate that the debug-info somehow wrong?


> But gdb.dwarf2/rnglists-multiple-cus.exp is expected to fail if you don't
> have the other patches in my series.
>  
>> I always thought that the partial symbols are replaced by the
>> full symbols as soon as the first item from the CU is accessed, say "main".
>> Can you explain how that can be?
>> I was never able to get a reproducer for partial symbols with only one CU.
> 
> The bug fixed by this patch triggers as soon as you have a function
> (DW_TAG_subprogram) with a DW_AT_ranges, I don't think it matters whether
> there is one or more CUs.  But perhaps it's difficult to force the compiler
> to emit a function with DW_AT_ranges (so, with a non-contiguous range) when
> using a single CU.
> 

It happens pretty reliably when you have a function that contains an error
handling that looks obvously "unlinkely" to the compiler, because it is guarded
by an if-condition and calls abort(), while there are also code paths that
don't call about.  The parts that call abort are then in a separate cold section.


Bernd.