[Bug gdb/29747] New: Crash when stepping over printf without debug symbols

["simark at simark dot ca" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29747

            Bug ID: 29747
           Summary: Crash when stepping over printf without debug symbols
           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: ---

$ cat test.c
#include <stdio.h>

int main()
{
  printf("Hi\n");
  return 0;
}
$ gcc test.c -O0 -o test 
$ ./gdb -q -nx --data-directory=data-directory test -ex start -ex s
Reading symbols from test...
(No debugging symbols found in test)
Temporary breakpoint 1 at 0x1151
Starting program: /home/smarchi/build/binutils-gdb/gdb/test 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Temporary breakpoint 1, 0x0000555555555151 in main ()
Single stepping until exit from function main,
which has no line number information.
/home/smarchi/src/binutils-gdb/gdb/infrun.c:6960:64: runtime error: member call
on null pointer of type 'struct symbol'

The crash happens here:

#0  __sanitizer::Die () at
../../../../src/libsanitizer/sanitizer_common/sanitizer_termination.cpp:50
#1  0x00007ffff5dd7128 in __ubsan::__ubsan_handle_type_mismatch_v1_abort
(Data=<optimized out>, Pointer=<optimized out>) at
../../../../src/libsanitizer/ubsan/ubsan_handlers.cpp:148
#2  0x000055556183e1a7 in process_event_stop_test (ecs=0x7fffffffccd0) at
/home/smarchi/src/binutils-gdb/gdb/infrun.c:6960
#3  0x0000555561838ea4 in handle_signal_stop (ecs=0x7fffffffccd0) at
/home/smarchi/src/binutils-gdb/gdb/infrun.c:6615
#4  0x000055556182f77b in handle_inferior_event (ecs=0x7fffffffccd0) at
/home/smarchi/src/binutils-gdb/gdb/infrun.c:5866


In this code:

  if (execution_direction != EXEC_REVERSE
      && ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE
      && in_solib_dynsym_resolve_code (ecs->event_thread->stop_pc ())
      && !in_solib_dynsym_resolve_code (
          ecs->event_thread->control.step_start_function->value_block ()
              ->entry_pc ()))

ecs->event_thread->control.step_start_function is nullptr and gets
dereferenced.

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