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* [Bug gdb/31070] New: Abnormal Jump in Execution for builtin function using 'stepi' Command in GDB
@ 2023-11-16  7:24 iamanonymous.cs at gmail dot com
  2023-11-16  7:25 ` [Bug gdb/31070] " iamanonymous.cs at gmail dot com
                   ` (8 more replies)
  0 siblings, 9 replies; 10+ messages in thread
From: iamanonymous.cs at gmail dot com @ 2023-11-16  7:24 UTC (permalink / raw)
  To: gdb-prs

https://sourceware.org/bugzilla/show_bug.cgi?id=31070

            Bug ID: 31070
           Summary: Abnormal Jump in Execution for builtin function using
                    'stepi' Command in GDB
           Product: gdb
           Version: unknown
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: iamanonymous.cs at gmail dot com
  Target Milestone: ---

$ gcc --version
gcc (GCC) 13.0.0 20221107 (experimental)
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gdb --version
GNU gdb (GDB) 14.0.50.20230417-git
Copyright (C) 2023 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

$ gdb -q a.out
Reading symbols from a.out...
(gdb) b main
Breakpoint 1 at 0x401040: file small.c, line 29.
(gdb) r
Starting program: /root/devil/a.out 

Breakpoint 1, main () at small.c:29
29        __builtin_prefetch (glob_int_arr, 0, 0);
(gdb) si
0x0000000000401044 in simple_global () at small.c:30
30        __builtin_prefetch (glob_ptr_int, 0, 0);
(gdb) si
0x000000000040104b in main () at small.c:151
151       exit (0);
(gdb) 

=================================================
When using the 'stepi' command in GDB, an abnormal jump in the execution occurs
when reaching line 30. The execution unexpectedly jumps to line 151.

Additional Information: Source-level stepping (e.g., 'next' or 'step') works
fine without any abnormal jumps. 
I was wondering that this might be a bug in gdb. 





This is the test program in gcc test suite
(gcc-12.1.0/gcc/testsuite/gcc.c-torture/execute/builtin-prefetch-2.c). 

$ cat small.c
/* Test that __builtin_prefetch does no harm.

   Prefetch data using a variety of storage classes and address
   expressions.  */

int glob_int_arr[100];
int *glob_ptr_int = glob_int_arr;
int glob_int = 4;

static stat_int_arr[100];
static int *stat_ptr_int = stat_int_arr;
static int stat_int;

struct S {
  int a;
  short b, c;
  char d[8];
  struct S *next;
};

struct S str;
struct S *ptr_str = &str;

/* Prefetch global variables using the address of the variable.  */

void
simple_global ()
{
  __builtin_prefetch (glob_int_arr, 0, 0);
  __builtin_prefetch (glob_ptr_int, 0, 0);
  __builtin_prefetch (&glob_int, 0, 0);
}

/* Prefetch file-level static variables using the address of the variable.  */

void
simple_file ()
{
  __builtin_prefetch (stat_int_arr, 0, 0);
  __builtin_prefetch (stat_ptr_int, 0, 0);
  __builtin_prefetch (&stat_int, 0, 0);
}

/* Prefetch local static variables using the address of the variable.  */

void
simple_static_local ()
{
  static int gx[100];
  static int *hx = gx;
  static int ix;
  __builtin_prefetch (gx, 0, 0);
  __builtin_prefetch (hx, 0, 0);
  __builtin_prefetch (&ix, 0, 0);
}

/* Prefetch local stack variables using the address of the variable.  */

void
simple_local ()
{
  int gx[100];
  int *hx = gx;
  int ix;
  __builtin_prefetch (gx, 0, 0);
  __builtin_prefetch (hx, 0, 0);
  __builtin_prefetch (&ix, 0, 0);
}

/* Prefetch arguments using the address of the variable.  */

void
simple_arg (int g[100], int *h, int i)
{
  __builtin_prefetch (g, 0, 0);
  __builtin_prefetch (h, 0, 0);
  __builtin_prefetch (&i, 0, 0);
}

/* Prefetch using address expressions involving global variables.  */

void
expr_global (void)
{
  __builtin_prefetch (&str, 0, 0);
  __builtin_prefetch (ptr_str, 0, 0);
  __builtin_prefetch (&str.b, 0, 0);
  __builtin_prefetch (&ptr_str->b, 0, 0);
  __builtin_prefetch (&str.d, 0, 0);
  __builtin_prefetch (&ptr_str->d, 0, 0);
  __builtin_prefetch (str.next, 0, 0);
  __builtin_prefetch (ptr_str->next, 0, 0);
  __builtin_prefetch (str.next->d, 0, 0);
  __builtin_prefetch (ptr_str->next->d, 0, 0);

  __builtin_prefetch (&glob_int_arr, 0, 0);
  __builtin_prefetch (glob_ptr_int, 0, 0);
  __builtin_prefetch (&glob_int_arr[2], 0, 0);
  __builtin_prefetch (&glob_ptr_int[3], 0, 0);
  __builtin_prefetch (glob_int_arr+3, 0, 0);
  __builtin_prefetch (glob_int_arr+glob_int, 0, 0);
  __builtin_prefetch (glob_ptr_int+5, 0, 0);
  __builtin_prefetch (glob_ptr_int+glob_int, 0, 0);
}

/* Prefetch using address expressions involving local variables.  */

void
expr_local (void)
{
  int b[10];
  int *pb = b;
  struct S t;
  struct S *pt = &t;
  int j = 4;

  __builtin_prefetch (&t, 0, 0);
  __builtin_prefetch (pt, 0, 0);
  __builtin_prefetch (&t.b, 0, 0);
  __builtin_prefetch (&pt->b, 0, 0);
  __builtin_prefetch (&t.d, 0, 0);
  __builtin_prefetch (&pt->d, 0, 0);
  __builtin_prefetch (t.next, 0, 0);
  __builtin_prefetch (pt->next, 0, 0);
  __builtin_prefetch (t.next->d, 0, 0);
  __builtin_prefetch (pt->next->d, 0, 0);

  __builtin_prefetch (&b, 0, 0);
  __builtin_prefetch (pb, 0, 0);
  __builtin_prefetch (&b[2], 0, 0);
  __builtin_prefetch (&pb[3], 0, 0);
  __builtin_prefetch (b+3, 0, 0);
  __builtin_prefetch (b+j, 0, 0);
  __builtin_prefetch (pb+5, 0, 0);
  __builtin_prefetch (pb+j, 0, 0);
}

int
main ()
{
  simple_global ();
  simple_file ();
  simple_static_local ();
  simple_local ();
  simple_arg (glob_int_arr, glob_ptr_int, glob_int);

  str.next = &str;
  expr_global ();
  expr_local ();

  exit (0);
}

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-- links below jump to the message on this page --
2023-11-16  7:24 [Bug gdb/31070] New: Abnormal Jump in Execution for builtin function using 'stepi' Command in GDB iamanonymous.cs at gmail dot com
2023-11-16  7:25 ` [Bug gdb/31070] " iamanonymous.cs at gmail dot com
2023-11-16  7:27 ` iamanonymous.cs at gmail dot com
2023-11-16  7:28 ` iamanonymous.cs at gmail dot com
2023-11-16  8:26 ` iamanonymous.cs at gmail dot com
2023-11-16  8:33 ` iamanonymous.cs at gmail dot com
2023-11-16 11:36 ` vries at gcc dot gnu.org
2023-11-16 11:54 ` iamanonymous.cs at gmail dot com
2023-11-16 11:56 ` vries at gcc dot gnu.org
2023-11-16 11:59 ` iamanonymous.cs at gmail dot com

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