Passing Ada Proc as a C Function Pointer
in [ADA]
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From: Warren on 5 Aug 2010 11:37 On Aug 5, 10:31 am, Warren <ve3...(a)gmail.com> wrote: > On Aug 5, 3:33 am, Rolf <rolf.ebert_nosp...(a)gmx.net> wrote: ... > When I compile the above, I get the complaint: > > avr_threads.ads:58:33: size for "C_Context_Type" too small, minimum > allowed is 112 > > 112 bytes - yikers! How do I get this right? > > Warren Arg!!!! Arg!!!! I keep thinking in terms of bytes - not BITS!! No wonder! Warren
From: Warren on 5 Aug 2010 12:51 On Aug 5, 11:37 am, Warren <ve3...(a)gmail.com> wrote: > Arg!!!! Arg!!!! > > I keep thinking in terms of bytes - not BITS!! No wonder! > > Warren At long last-- it works!!!! I ended up creating a C routine for the launch: void avr_thread_start_ada( avr_thread_context* context, uint8_t* stack, uint16_t stack_size) { extern void thread_thunk(void); /* Ada in C convention */ avr_thread_start(context,thread_thunk,stack,stack_size); } which is called by Start_Thread in Ada. This then invokes the usual avr_thread_start(), which then launches the Ada (in C convention) routine Thread_Thunk: procedure Thread_Thunk; pragma export(C,Thread_Thunk,"thread_thunk"); procedure Thread_Thunk is Context : Thread_Context_Ptr := Get_Context; begin Context.Ada_Proc.all; -- Start Ada code in new thread end Thread_Thunk; There was an undocumented AVR_Threads routine in the include file that allowed me to pick up the active context, which is used by Ada routine binding Get_Context. The context object turned out to be tricky because the C context object needed to be "struct aligned", which appears to be 64-bit. So a little work on that fixed it. I also rolled the stack into the object as a variant record, for user convenience: type Thread_Context(Stack_Size : Unsigned_16) is record C_Context : aliased C_Context_Type; Ada_Proc : Thread_Proc; Stack : aliased Stack_Type(1..Stack_Size); end record; for Thread_Context use record C_Context at 0 range 0 .. 16 * 8 -1; -- Must be first to be 64-bit aligned Stack_Size at 16 range 0 .. 15; -- Moved here - non critical Ada_Proc at 18 range 0 .. 15; -- Non critical placement -- Stack at 20 range 0 .. Stack_Size * 8 - 1; end record; Thanks to everyone for their comments and ideas. Warren
From: Simon Wright on 5 Aug 2010 16:50
Rolf <rolf.ebert_nospam_(a)gmx.net> writes: >> > There may be a pragma to prevent secondary stack usage? >> >> I'm all ears! ;-) > > pragma Restrictions (No_Secondary_Stack); > > It is already active if you use AVR-Ada. See the file gnat.adc One fewer thing to worry about, then! |