Re: [PING 2][PATCH PR gdb/18071] TLS variables can't be resolved on aarch64-linux-gnu

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Re: [PING 2][PATCH PR gdb/18071] TLS variables can't be resolved on aarch64-linux-gnu

Wei-min Pan

On 11/15/2017 5:51 PM, Wei-min Pan wrote:

>
> On 11/2/2017 8:32 AM, Weimin Pan wrote:
>> Running the test case with upstream gdb shows two failures:
>>
>> (1) Receiving different error messages when printing TLS variable before
>>      program runs - because the ARM compiler does not emit dwarf
>> attribute
>>      DW_AT_location for TLS, the result is expected and the baseline may
>>      need to be changed for aarch64.
>>
>> (2) Using "info address" command on C++ static TLS object resulted in
>>      "symbol unresolved" error - below is a snippet from the test case:
>>
>> class K {
>>   public:
>>    static __thread int another_thread_local;
>> };
>>
>> __thread int K::another_thread_local;
>>
>> (gdb) info address K::another_thread_local
>> Symbol "K::another_thread_local" is unresolved.
>>
>> This patch contains fix for (2).
>>
>> Function info_address_command() handles the "info address" command and
>> calls lookup_minimal_symbol_and_objfile() to find sym's symbol entry in
>> mininal symbol table if SYMBOL_COMPUTED_OPS (sym) is false. Problem is
>> that function lookup_minimal_symbol_and_objfile() only looked up an
>> objfile's minsym ordinary hash table, not its demangled hash table,
>> which
>> was the reason why the C++ name was not found.
>>
>> The fix is to call lookup_minimal_symbol(), which already looks up
>> entries
>> in both minsym's hash tables, to find names when traversing the
>> object file
>> list in lookup_minimal_symbol_and_objfile().
>>
>> Tested in both aarch64-linux-gnu and amd64-linux-gnu. No regressions.
>> ---
>>   gdb/ChangeLog |    5 +++++
>>   gdb/minsyms.c |   17 +++--------------
>>   2 files changed, 8 insertions(+), 14 deletions(-)
>>
>> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
>> index 4b292e0..2f630bc 100644
>> --- a/gdb/ChangeLog
>> +++ b/gdb/ChangeLog
>> @@ -1,3 +1,8 @@
>> +2017-11-01  Weimin Pan  <[hidden email]>
>> +
>> +    * minsyms.c (lookup_minimal_symbol_and_objfile): Use
>> +    lookup_minimal_symbol() to find symbol entry.
>> +
>>   2017-10-27  Keith Seitz  <[hidden email]>
>>         * breakpoint.c (print_breakpoint_location): Use the symbol saved
>> diff --git a/gdb/minsyms.c b/gdb/minsyms.c
>> index 37edbd8..4edd8b1 100644
>> --- a/gdb/minsyms.c
>> +++ b/gdb/minsyms.c
>> @@ -881,23 +881,12 @@ lookup_minimal_symbol_and_objfile (const char
>> *name)
>>   {
>>     struct bound_minimal_symbol result;
>>     struct objfile *objfile;
>> -  unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;
>>       ALL_OBJFILES (objfile)
>>       {
>> -      struct minimal_symbol *msym;
>> -
>> -      for (msym = objfile->per_bfd->msymbol_hash[hash];
>> -       msym != NULL;
>> -       msym = msym->hash_next)
>> -    {
>> -      if (strcmp (MSYMBOL_LINKAGE_NAME (msym), name) == 0)
>> -        {
>> -          result.minsym = msym;
>> -          result.objfile = objfile;
>> -          return result;
>> -        }
>> -    }
>> +      result = lookup_minimal_symbol (name, NULL, objfile);
>> +      if (result.minsym != NULL)
>> +        return result;
>>       }
>>       memset (&result, 0, sizeof (result));
>