GNU Compiler Collection (GCC) Internals: Miscellaneous routines

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### 4.6 Miscellaneous runtime library routines

#### 4.6.1 Cache control functions

Runtime Function: void __clear_cache (char *beg, char *end)

  This function clears the instruction cache between beg and end.

#### 4.6.2 Split stack functions and variables

Runtime Function: void * __splitstack_find (void *segment_arg, void *sp, size_t len, void **next_segment, void **next_sp, void **initial_sp)

  When using `-fsplit-stack`, this call may be used to iterate over the stack segments. It may be called like this:

        void *next_segment = NULL;
        void *next_sp = NULL;
        void *initial_sp = NULL;
        void *stack;
        size_t stack_size;
        while ((stack = __splitstack_find (next_segment, next_sp,
                                           &stack_size, &next_segment,
                                           &next_sp, &initial_sp))
               != NULL)
          {
            /* Stack segment starts at stack and is
               stack_size bytes long.  */
          }

  There is no way to iterate over the stack segments of a different thread. However, what is permitted is for one thread to call this with the segment_arg and sp arguments NULL, to pass next_segment, next_sp, and initial_sp to a different thread, and then to suspend one way or another. A different thread may run the subsequent `__splitstack_find` iterations. Of course, this will only work if the first thread is suspended while the second thread is calling `__splitstack_find`. If not, the second thread could be looking at the stack while it is changing, and anything could happen.

Variable: __morestack_segments
Variable: __morestack_current_segment
Variable: __morestack_initial_sp

  Internal variables used by the `-fsplit-stack` implementation.