gcc/doc/gccint/the-gcc-low-level-runtime-library/miscellaneous-runtime-library-routines.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. _miscellaneous-routines:
   7
   8 Miscellaneous runtime library routines
   9 **************************************
  10
  11 Cache control functions
  12 ^^^^^^^^^^^^^^^^^^^^^^^
  13
  14 .. function:: void __clear_cache (char *beg, char *end)
  15
  16   This function clears the instruction cache between :samp:`{beg}` and :samp:`{end}`.
  17
  18 Split stack functions and variables
  19 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  20
  21 .. function:: void * __splitstack_find (void *segment_arg, void *sp, size_t len, void **next_segment, void **next_sp, void **initial_sp)
  22
  23   When using :option:`-fsplit-stack`, this call may be used to iterate
  24   over the stack segments.  It may be called like this:
  25
  26   .. code-block:: c++
  27
  28       void *next_segment = NULL;
  29       void *next_sp = NULL;
  30       void *initial_sp = NULL;
  31       void *stack;
  32       size_t stack_size;
  33       while ((stack = __splitstack_find (next_segment, next_sp,
  34                                          &stack_size, &next_segment,
  35                                          &next_sp, &initial_sp))
  36              != NULL)
  37         {
  38           /* Stack segment starts at stack and is
  39              stack_size bytes long.  */
  40         }
  41
  42   There is no way to iterate over the stack segments of a different
  43   thread.  However, what is permitted is for one thread to call this
  44   with the :samp:`{segment_arg}` and :samp:`{sp}` arguments NULL, to pass
  45   :samp:`{next_segment}`, :samp:`{next_sp}`, and :samp:`{initial_sp}` to a different
  46   thread, and then to suspend one way or another.  A different thread
  47   may run the subsequent ``__splitstack_find`` iterations.  Of
  48   course, this will only work if the first thread is suspended while the
  49   second thread is calling ``__splitstack_find``.  If not, the second
  50   thread could be looking at the stack while it is changing, and
  51   anything could happen.
  52
  53 .. c:var:: struct stack_segment *__morestack_segments
  54
  55 .. c:var:: stack_segment * __morestack_current_segment
  56
  57 .. c:var:: struct initial_sp __morestack_initial_sp
  58
  59 Internal variables used by the :option:`-fsplit-stack` implementation.