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

Wei-min Pan
2017-11-16T01:53:49Z

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 <weimin.pan@oracle.com>
> +
> + * minsyms.c (lookup_minimal_symbol_and_objfile): Use
> + lookup_minimal_symbol() to find symbol entry.
> +
> 2017-10-27 Keith Seitz <keiths@redhat.com>
>
> * 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));