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/*$Id: genarch.c,v 1.1.1.2 1999/02/22 03:04:22 scottc Exp $ */
/* Generate a header file (arch.h) with parameters */
/* reflecting the machine architecture and compiler characteristics. */

#include "stdpre.h"
#include <stdio.h>

/* We should write the result on stdout, but the original Turbo C 'make' */
/* can't handle output redirection (sigh). */

private void
section(FILE * f, char *str)
{
    fprintf(f, "\n\t /* ---------------- %s ---------------- */\n\n", str);
}

int
main(int argc, char *argv[])
{
    char *fname = argv[1];
    long one = 1;
    char *ffs = "ffffffffffffffff";	/* 8 bytes */
    int ffs_strlen = strlen(ffs);
    struct {
	char c;
	short s;
    } ss;
    struct {
	char c;
	int i;
    } si;
    struct {
	char c;
	long l;
    } sl;
    struct {
	char c;
	char *p;
    } sp;
    struct {
	char c;
	float f;
    } sf;
    struct {
	char c;
	double d;
    } sd;
    static int log2s[17] =
    {0, 0, 1, 0, 2, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 4};
    long lm1 = -1;
    long lr1 = lm1 >> 1, lr2 = lm1 >> 2;
    unsigned long um1 = ~(unsigned long)0;
    int im1 = -1;
    int ir1 = im1 >> 1, ir2 = im1 >> 2;
    union {
	long l;
	char *p;
    } pl0, pl1;
    int ars;
    int lwidth = size_of(long) * 8;
    union {
	float f;
	int i;
	long l;
    } f0 , f1, fm1;
    FILE *f = fopen(fname, "w");

    if (f == NULL) {
	fprintf(stderr, "genarch.c: can't open %s for writing\n", fname);
	return exit_FAILED;
    }
    fprintf(f, "/* Parameters derived from machine and compiler architecture */\n");

    section(f, "Scalar alignments");

#define OFFSET_IN(s, e) (int)((char *)&s.e - (char *)&s)
    fprintf(f, "#define arch_align_short_mod %d\n", OFFSET_IN(ss, s));
    fprintf(f, "#define arch_align_int_mod %d\n", OFFSET_IN(si, i));
    fprintf(f, "#define arch_align_long_mod %d\n", OFFSET_IN(sl, l));
    fprintf(f, "#define arch_align_ptr_mod %d\n", OFFSET_IN(sp, p));
    fprintf(f, "#define arch_align_float_mod %d\n", OFFSET_IN(sf, f));
    fprintf(f, "#define arch_align_double_mod %d\n", OFFSET_IN(sd, d));
#undef OFFSET_IN

    section(f, "Scalar sizes");

    fprintf(f, "#define arch_log2_sizeof_short %d\n", log2s[size_of(short)]);
    fprintf(f, "#define arch_log2_sizeof_int %d\n", log2s[size_of(int)]);
    fprintf(f, "#define arch_log2_sizeof_long %d\n", log2s[size_of(long)]);
    fprintf(f, "#define arch_sizeof_ptr %d\n", size_of(char *));
    fprintf(f, "#define arch_sizeof_float %d\n", size_of(float));
    fprintf(f, "#define arch_sizeof_double %d\n", size_of(double));

    section(f, "Unsigned max values");

#define PRINT_MAX(str, typ, tstr, l)\
  fprintf(f, "#define arch_max_%s ((%s)0x%s%s + (%s)0)\n",\
    str, tstr, ffs + ffs_strlen - size_of(typ) * 2, l, tstr)
    PRINT_MAX("uchar", unsigned char, "unsigned char", "");
    PRINT_MAX("ushort", unsigned short, "unsigned short", "");
    PRINT_MAX("uint", unsigned int, "unsigned int", "");
    PRINT_MAX("ulong", unsigned long, "unsigned long", "L");

#undef PRINT_MAX

    section(f, "Miscellaneous");

    fprintf(f, "#define arch_is_big_endian %d\n", 1 - *(char *)&one);
    pl0.l = 0;
    pl1.l = -1;
    fprintf(f, "#define arch_ptrs_are_signed %d\n",
	    (pl1.p < pl0.p));
    f0.f = 0.0, f1.f = 1.0, fm1.f = -1.0;
    /* We have to test the size dynamically here, */
    /* because the preprocessor can't evaluate sizeof. */
    fprintf(f, "#define arch_floats_are_IEEE %d\n",
	    ((size_of(float) == size_of(int) ?
	  f0.i == 0 && f1.i == (int)0x3f800000 && fm1.i == (int)0xbf800000 :
	      f0.l == 0 && f1.l == 0x3f800000L && fm1.l == 0xbf800000L)
	     ? 1 : 0));

    /* There are three cases for arithmetic right shift: */
    /* always correct, correct except for right-shifting a long by 1 */
    /* (a bug in some versions of the Turbo C compiler), and */
    /* never correct. */
    ars = (lr2 != -1 || ir1 != -1 || ir2 != -1 ? 0 :
	   lr1 != -1 ? 1 :	/* Turbo C problem */
	   2);
    fprintf(f, "#define arch_arith_rshift %d\n", ars);
    /* Some machines can't handle a variable shift by */
    /* the full width of a long. */
    fprintf(f, "#define arch_can_shift_full_long %d\n",
	    um1 >> lwidth == 0);

/* ---------------- Done. ---------------- */

    fclose(f);
    return exit_OK;
}
