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gcc 4.4.1 - 4.6.0 compiler bug workaround.

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This commit is contained in:
David Kopf 2011-07-31 15:36:01 -04:00
parent 5330dd1565
commit df70b21c70
1 changed files with 10 additions and 1 deletions
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11
core/net/uip6.c
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@ -355,7 +355,16 @@ uip_ipchksum(void)
static u16_t
upper_layer_chksum(u8_t proto)
{
u16_t upper_layer_len;
/* gcc 4.4.0 - 4.6.1 (maybe 4.3...) with -Os on 8 bit CPUS incorrectly compiles:
* int bar (int);
* int foo (unsigned char a, unsigned char b) {
* int len = (a << 8) + b; //len becomes 0xff00&<random>+b
* return len + bar (len);
* }
* upper_layer_len triggers this bug unless it is declared volatile.
* See https://sourceforge.net/apps/mantisbt/contiki/view.php?id=3
*/
volatile u16_t upper_layer_len;
u16_t sum;
upper_layer_len = (((u16_t)(UIP_IP_BUF->len[0]) << 8) + UIP_IP_BUF->len[1] - uip_ext_len) ;