Miscellaneous routines - GNU Compiler Collection (GCC) Internals
Description: GNU Compiler Collection (GCC) Internals

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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.