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Over-engineer byte-order macro generation to catch most PDP-endian situations (65230, r=rogerl, not part of Mozilla-the-browser-suite build).

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brendan%mozilla.org 2001-04-17 07:12:38 +00:00
parent ffc473a9b0
commit 00e6bf0cdc
1 changed files with 69 additions and 39 deletions
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108
js/src/jscpucfg.c
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@ -139,41 +139,6 @@ static int Log2(unsigned int n)
return log2;
}
/* We assume that int's are 32 bits */
static void do64(void)
{
union {
long i;
char c[4];
} u;
u.i = 0x01020304;
if (u.c[0] == 0x01) {
printf("#undef IS_LITTLE_ENDIAN\n");
printf("#define IS_BIG_ENDIAN 1\n\n");
} else {
printf("#define IS_LITTLE_ENDIAN 1\n");
printf("#undef IS_BIG_ENDIAN\n\n");
}
}
static void do32(void)
{
union {
long i;
char c[4];
} u;
u.i = 0x01020304;
if (u.c[0] == 0x01) {
printf("#undef IS_LITTLE_ENDIAN\n");
printf("#define IS_BIG_ENDIAN 1\n\n");
} else {
printf("#define IS_LITTLE_ENDIAN 1\n");
printf("#undef IS_BIG_ENDIAN\n\n");
}
}
/*
* Conceivably this could actually be used, but there is lots of code out
* there with ands and shifts in it that assumes a byte is exactly 8 bits,
@ -232,10 +197,75 @@ int main(int argc, char **argv)
align_of_word = PR_ALIGN_OF_WORD;
#else /* !CROSS_COMPILE */
if (sizeof(long) == 8) {
do64();
} else {
do32();
/*
* We don't handle PDP-endian or similar orders: if a short is big-endian,
* so must int and long be big-endian for us to generate the IS_BIG_ENDIAN
* #define and the IS_LITTLE_ENDIAN #undef.
*/
{
int big_endian = 0, little_endian = 0, ntests = 0;
if (sizeof(short) == 2) {
union {
short i;
char c[2];
} u;
u.i = 0x0102;
big_endian += (u.c[0] == 0x01 && u.c[1] == 0x02);
little_endian += (u.c[0] == 0x02 && u.c[1] == 0x01);
ntests++;
}
if (sizeof(int) == 4) {
union {
int i;
char c[4];
} u;
u.i = 0x01020304;
big_endian += (u.c[0] == 0x01 && u.c[1] == 0x02 &&
u.c[2] == 0x03 && u.c[3] == 0x04);
little_endian += (u.c[0] == 0x04 && u.c[1] == 0x03 &&
u.c[2] == 0x02 && u.c[3] == 0x01);
ntests++;
}
if (sizeof(long) == 8) {
union {
long i;
char c[8];
} u;
/*
* Write this as portably as possible: avoid 0x0102030405060708L
* and <<= 32.
*/
u.i = 0x01020304;
u.i <<= 16, u.i <<= 16;
u.i |= 0x05060708;
big_endian += (u.c[0] == 0x01 && u.c[1] == 0x02 &&
u.c[2] == 0x03 && u.c[3] == 0x04 &&
u.c[4] == 0x05 && u.c[5] == 0x06 &&
u.c[6] == 0x07 && u.c[7] == 0x08);
little_endian += (u.c[0] == 0x08 && u.c[1] == 0x07 &&
u.c[2] == 0x06 && u.c[3] == 0x05 &&
u.c[4] == 0x04 && u.c[5] == 0x03 &&
u.c[6] == 0x02 && u.c[7] == 0x01);
ntests++;
}
if (big_endian && big_endian == ntests) {
printf("#undef IS_LITTLE_ENDIAN\n");
printf("#define IS_BIG_ENDIAN 1\n\n");
} else if (little_endian && little_endian == ntests) {
printf("#define IS_LITTLE_ENDIAN 1\n");
printf("#undef IS_BIG_ENDIAN\n\n");
} else {
fprintf(stderr, "%s: unknown byte order!\n", argv[0]);
return 1;
}
}
sizeof_char = sizeof(char);