[Bug backtrace/29395] New: blockframe.c:79: internal-error: get_frame_block: Assertion `bl != NULL' failed.

["georgepee at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29395

            Bug ID: 29395
           Summary: blockframe.c:79: internal-error: get_frame_block:
                    Assertion `bl != NULL' failed.
           Product: gdb
           Version: 11.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: backtrace
          Assignee: unassigned at sourceware dot org
          Reporter: georgepee at gmail dot com
  Target Milestone: ---

Starting with gdb 11.x, I encounter this assertion failure on certain
backtraces

../../gdb/blockframe.c:79: internal-error: get_frame_block: Assertion `bl !=
NULL' failed.


Not really knowing much about the GDB and DWARF structures, I did this as an
experiment and then GDB 11.x shows the same backtrace that GDB 10.x did. 

```
diff --git a/gdb/blockframe.c b/gdb/blockframe.c
index 50c464f44a2..0ee8313abea 100644
--- a/gdb/blockframe.c
+++ b/gdb/blockframe.c
@@ -70,13 +70,12 @@ get_frame_block (struct frame_info *frame, CORE_ADDR
*addr_in_block)

   inline_count = frame_inlined_callees (frame);

-  while (inline_count > 0)
+  while (bl && (inline_count > 0))
     {
       if (block_inlined_p (bl))
-   inline_count--;
+          inline_count--;

       bl = BLOCK_SUPERBLOCK (bl);
-      gdb_assert (bl != NULL);
     }

   return bl;
```

Comparing the values of frame_inlined_callees() from GDB 10.x and 11.x, I see
that they differ.

I also tried GDB 12.1, and it outputs this:
```
../../gdb/blockframe.c:79: internal-error: get_frame_block: Assertion `bl !=
NULL' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
----- Backtrace -----
0x55a42dc123b7 gdb_internal_backtrace_1
        ../../gdb/bt-utils.c:122
0x55a42dc123b7 _Z22gdb_internal_backtracev
        ../../gdb/bt-utils.c:168
0x55a42defaeec internal_vproblem
        ../../gdb/utils.c:394
0x55a42defb10a _Z15internal_verrorPKciS0_P13__va_list_tag
        ../../gdb/utils.c:471
0x55a42e034a71 _Z14internal_errorPKciS0_z
        ../../gdbsupport/errors.cc:55
0x55a42dbe9968 _Z15get_frame_blockP10frame_infoPm
        ../../gdb/blockframe.c:79
0x55a42dbe9968 _Z15get_frame_blockP10frame_infoPm
        ../../gdb/blockframe.c:55
0x55a42dc9e622 _ZN18dwarf_expr_context14get_frame_baseEPPKhPm
        ../../gdb/dwarf2/expr.c:782
0x55a42dca0346 _ZN18dwarf_expr_context16execute_stack_opEPKhS1_
        ../../gdb/dwarf2/expr.c:1821
0x55a42dca1c53 _ZN18dwarf_expr_context4evalEPKhm
        ../../gdb/dwarf2/expr.c:1250
0x55a42dca1dee
_ZN18dwarf_expr_context26push_dwarf_reg_entry_valueE24call_site_parameter_kind21call_site_parameter_ui
        ../../gdb/dwarf2/expr.c:914
0x55a42dca12bb _ZN18dwarf_expr_context16execute_stack_opEPKhS1_
        ../../gdb/dwarf2/expr.c:2259
0x55a42dca1c53 _ZN18dwarf_expr_context4evalEPKhm
        ../../gdb/dwarf2/expr.c:1250
0x55a42dca1ea2
_ZN18dwarf_expr_context8evaluateEPKhmbP18dwarf2_per_cu_dataP10frame_infoPK18property_addr_infoP4typeSA_l
        ../../gdb/dwarf2/expr.c:1089
0x55a42dcb43a0 dwarf2_evaluate_loc_desc_full
        ../../gdb/dwarf2/loc.c:1485
0x55a42dcb4e37
_Z24dwarf2_evaluate_loc_descP4typeP10frame_infoPKhmP18dwarf2_per_cu_dataP18dwarf2_per_objfileb
        ../../gdb/dwarf2/loc.c:1529
0x55a42dcb4e37 loclist_read_variable
        ../../gdb/dwarf2/loc.c:3859
0x55a42dd14279
_ZNK13language_defn14read_var_valueEP6symbolPK5blockP10frame_info
        ../../gdb/findvar.c:617
0x55a42de8bbd0
_Z14read_frame_argRK19frame_print_optionsP6symbolP10frame_infoP9frame_argS7_
        ../../gdb/stack.c:540
0x55a42de8c5c4 print_frame_args
        ../../gdb/stack.c:888
0x55a42de8ddb3 print_frame
        ../../gdb/stack.c:1391
0x55a42de8ddb3
_Z16print_frame_infoRK19frame_print_optionsP10frame_infoi10print_whatii
        ../../gdb/stack.c:1117
0x55a42de8f55a backtrace_command_1
        ../../gdb/stack.c:2069
0x55a42de8f55a backtrace_command
        ../../gdb/stack.c:2188
0x55a42dc3e8a7 _Z8cmd_funcP16cmd_list_elementPKci
        ../../gdb/cli/cli-decode.c:2514
0x55a42dee0766 _Z15execute_commandPKci
        ../../gdb/top.c:702
0x55a42dcfce9b _Z15command_handlerPKc
        ../../gdb/event-top.c:597
0x55a42dcfd1cc
_Z20command_line_handlerOSt10unique_ptrIcN3gdb13xfree_deleterIcEEE
        ../../gdb/event-top.c:800
0x55a42dcfd82c gdb_rl_callback_handler
        ../../gdb/event-top.c:229
0x7f9293ac8d4d ???
0x55a42dcfc2dd gdb_rl_callback_read_char_wrapper_noexcept
        ../../gdb/event-top.c:187
0x55a42dcfd720 gdb_rl_callback_read_char_wrapper
        ../../gdb/event-top.c:204
0x55a42dcfc06f _Z19stdin_event_handleriPv
        ../../gdb/event-top.c:524
0x55a42e035554 gdb_wait_for_event
        ../../gdbsupport/event-loop.cc:700
0x55a42e03563a gdb_wait_for_event
        ../../gdbsupport/event-loop.cc:596
0x55a42e03563a _Z16gdb_do_one_eventv
        ../../gdbsupport/event-loop.cc:237
0x55a42ddb0b54 start_event_loop
        ../../gdb/main.c:421
0x55a42ddb0b54 captured_command_loop
        ../../gdb/main.c:481
0x55a42ddb2564 captured_main
        ../../gdb/main.c:1351
0x55a42ddb2564 _Z8gdb_mainP18captured_main_args
        ../../gdb/main.c:1366
0x55a42db5970a main
        ../../gdb/gdb.c:32
```

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