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/*
                 Crown Copyright (c) 1997
    
    This TenDRA(r) Computer Program is subject to Copyright
    owned by the United Kingdom Secretary of State for Defence
    acting through the Defence Evaluation and Research Agency
    (DERA).  It is made available to Recipients with a
    royalty-free licence for its use, reproduction, transfer
    to other parties and amendment for any purpose not excluding
    product development provided that any such use et cetera
    shall be deemed to be acceptance of the following conditions:-
    
        (1) Its Recipients shall ensure that this Notice is
        reproduced upon any copies or amended versions of it;
    
        (2) Any amended version of it shall be clearly marked to
        show both the nature of and the organisation responsible
        for the relevant amendment or amendments;
    
        (3) Its onward transfer from a recipient to another
        party shall be deemed to be that party's acceptance of
        these conditions;
    
        (4) DERA gives no warranty or assurance as to its
        quality or suitability for any purpose and DERA accepts
        no liability whatsoever in relation to any use to which
        it may be put.
*/


/* This is intended for SGI IRIX 32-bit */

Common __TDFhandler:proc;
Common __mipshandler:proc;
Common __TDFstacklim:pointer(locals_alignment);

Tokdec ansi.signal.signal: [EXP, EXP]EXP;
Tokdec ansi.stdlib.exit: [EXP]EXP;

Tokdef SIGFPE = []SIGNED_NAT 8;
Tokdef SIGBUS = []SIGNED_NAT 10;
Tokdef SIGSEGV = []SIGNED_NAT 11;
Tokdef SIGUSR1 = []SIGNED_NAT 16;
        /* signal numbers - SIGUSR1 is used for stack overflow
        */

Tokdec ~Throw:[NAT]EXP;
        /* This token must be defined to throw the language specific error
        value
        */

Struct longptr(hi:Int, lo:Ptr proc);

Struct sigcontext(sc_onstack:Int, sc_mask:Int, 
                  sc_pc:longptr,
                  sc_regs:nof(32,longptr),
                  sc_fpregs:nof(32,longptr),
                  sc_ownedfp:Int,
                  sc_fpc_csr:Int, sc_fpc_eir:Int, 
                  sc_ssflags:Int,
                  sc_mdhi:longptr,
                  sc_mdlo:longptr,                
                  sc_cause:longptr, 
                  sc_badvaddr:longptr
                  );

Tokdef SETREG = [scp:EXP, r:NAT, val:EXP]EXP
        { ((scp *+. .sc_regs) *+. 
             (.lo .+. (Sizeof(longptr) .* (+ r(Int)) ))  ) = val };


Tokdef CAUSE_BD = []SIGNED_NAT 16r80000000;


Tokdef ~Set_signal_handler = [] EXP 
{
/* This token must be called before any possible exceptions */

 Let mh =  Proc top(sig:Int, code:Int, scp:Ptr sigcontext) {
  /* This procedure is obeyed at an automatic error trap, using signal.
   It's action calls __TDFhandler on top of the user stack by overwriting
   the relevant registers of the failing process and simply returning.
   Could have written this in C.
  */
        ((* scp *+. .sc_pc) *+. .lo) = * __TDFhandler; 
                /* the pc of the failing process */
        SETREG[* scp, 4, * sig];
                /* the first parameter */
        SETREG[* scp, 5, * code];
                /* the second parameter */
        SETREG[* scp, 25, * __TDFhandler];
                /* required for PIC code  */
        Let x = *(Int)(* scp *+. (.lo .+. .sc_cause))
        { (* scp *+. (.lo .+. .sc_cause)) = (x And not(CAUSE_BD(Int))) 
                /* the exception could have occurred in a delay slot
                   - make sure the return does not treat it as one.
                */      
        };
                
        return(make_top)
        /* reinstates the failing process ie does a call of __TDFhandler */
    }
 {
    __mipshandler = mh; 
    __TDFhandler = Proc top( sig:Int, code:Int)
   {
   /* This procedure may either be called via __mipshandler or else as a
   result of an explicit error test in the user program. It's action is to
   throw the language specific error coding. 
  */
   
   Labelled {
        Case * sig (SIGFPE -> overf, 
                    SIGBUS -> nilref1,
                    SIGSEGV -> nilref2, 
                    SIGUSR1 -> stackov)
        | :overf: 
                ansi.signal.signal[SIGFPE(Int), * __mipshandler];
                ~Throw[error_val(overflow)]
        | :nilref1:
                ansi.signal.signal[SIGBUS(Int), * __mipshandler]; 
                ~Throw[error_val(nil_access)]
        | :nilref2:
                ansi.signal.signal[SIGSEGV(Int), * __mipshandler]; 
                ~Throw[error_val(nil_access)]
        | :stackov:
                ansi.signal.signal[SIGUSR1(Int), * __mipshandler]; 
                ~Throw[error_val(stack_overflow)]
        /* other C signals can be treated similarly */
   };
   ansi.stdlib.exit[* sig];
   return(make_top);
  };

  ansi.signal.signal[SIGFPE(Int), * __mipshandler];
  ansi.signal.signal[SIGBUS(Int), * __mipshandler];
  ansi.signal.signal[SIGSEGV(Int), * __mipshandler];
  ansi.signal.signal[SIGUSR1(Int), * __mipshandler];
  env_size(mh) .+. (Sizeof(Char) .* 1000(Int))
 }
};

Tokdef ~Sync_handler = [] EXP make_top;

Keep (~Set_signal_handler, __TDFhandler, ~Sync_handler, __TDFstacklim)