\section[SMstacks.lc]{Stack allocation (sequential)}

Routine that allocates the A and B stack (sequential only).

\begin{code}
#ifndef PAR
# define NULL_REG_MAP
# include "SMinternal.h"

#if 1 /* ndef CONCURRENT */ /* HWL */
stackData stackInfo;
#endif

P_ stks_space = 0;

#ifdef CONCURRENT
EXTDATA_RO(StkO_static_info);
P_ MainStkO;
#endif

rtsBool
initStacks(smInfo *sm)
{
    /*
     * Allocate them if they don't exist. One space does for both stacks, since they
     * grow towards each other
     */
    if (stks_space == 0) {
#ifndef CONCURRENT
	stks_space = (P_) stgMallocWords(RTSflags.GcFlags.stksSize, "initStacks");
#else
	MainStkO = (P_) stgMallocWords(STKO_HS + RTSflags.GcFlags.stksSize, "initStacks");
	stks_space = MainStkO + STKO_HS;
        SET_STKO_HDR(MainStkO, StkO_static_info, CC_SUBSUMED);
        STKO_SIZE(MainStkO) = RTSflags.GcFlags.stksSize + STKO_VHS;
        STKO_SpB(MainStkO) = STKO_SuB(MainStkO) = STKO_BSTK_BOT(MainStkO) + BREL(1);
        STKO_SpA(MainStkO) = STKO_SuA(MainStkO) = STKO_ASTK_BOT(MainStkO) + AREL(1);
        STKO_LINK(MainStkO) = Prelude_Z91Z93_closure;
    	STKO_RETURN(MainStkO) = NULL;

	ASSERT(sanityChk_StkO(MainStkO));

    	if (RTSflags.GcFlags.trace)
	    fprintf(stderr, "STACK init: botA, spa: 0x%lx, 0x%lx\n            botB, spb: 0x%lx, 0x%lx\n",
	      (W_) STKO_ASTK_BOT(MainStkO), (W_) STKO_SpA(MainStkO), (W_) STKO_BSTK_BOT(MainStkO), (W_) STKO_SpB(MainStkO));
#endif
    }

# if STACK_CHECK_BY_PAGE_FAULT
    unmapMiddleStackPage((char *) stks_space, RTSflags.GcFlags.stksSize * sizeof(W_));
# endif

    /* Initialise Stack Info and pointers */
#if 1 /* ndef CONCURRENT */ /* HWL */
    stackInfo.botA = STK_A_FRAME_BASE(stks_space, RTSflags.GcFlags.stksSize);
    stackInfo.botB = STK_B_FRAME_BASE(stks_space, RTSflags.GcFlags.stksSize);

    MAIN_SuA = MAIN_SpA = stackInfo.botA + AREL(1);
    MAIN_SuB = MAIN_SpB = stackInfo.botB + BREL(1);

    if (RTSflags.GcFlags.trace)
	fprintf(stderr, "STACK init: botA, spa: 0x%lx, 0x%lx\n            botB, spb: 0x%lx, 0x%lx\n",
	  (W_) stackInfo.botA, (W_) MAIN_SpA, (W_) stackInfo.botB, (W_) MAIN_SpB);
#endif /* !CONCURRENT */

    return rtsTrue;
}

#endif /* not parallel */
\end{code}