shin.anzai@xxxxxxxxxxxxx writes:
> Hello,
>
> I got following warning message using gcc-3.4.6-3 on IA64 server;
>
> include/linux/smp_lock.h: In function `init':
> include/linux/smp_lock.h:60: warning: unsupported arg to `__builtin_return_address'
>
>
> The lock_kernel function referred by init is as follows;
>
> static inline void lock_kernel(void)
> {
> int depth = current->lock_depth+1;
> if (likely(!depth)) {
> get_kernel_lock();
> kernel_lock_trace_buffer[kernel_lock_trace_index%16] = current;
> kernel_lock_addr[kernel_lock_trace_index++%16]
> = __builtin_return_address(2);
> }
> current->lock_depth = depth;
> }
>
> Could you let me know how can I use __builtin_return_address?
This is once case where everything is complete in the documentation:
-- Built-in Function: void * __builtin_return_address (unsigned int
LEVEL)
This function returns the return address of the current function,
or of one of its callers. The LEVEL argument is number of frames
to scan up the call stack. A value of `0' yields the return
address of the current function, a value of `1' yields the return
address of the caller of the current function, and so forth. When
inlining the expected behavior is that the function will return
the address of the function that will be returned to. To work
around this behavior use the `noinline' function attribute.
The LEVEL argument must be a constant integer.
On some machines it may be impossible to determine the return
address of any function other than the current one; in such cases,
or when the top of the stack has been reached, this function will
return `0' or a random value. In addition,
`__builtin_frame_address' may be used to determine if the top of
the stack has been reached.
This function should only be used with a nonzero argument for
debugging purposes.
Andrew.
