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u3: make the fault handler robust against initialization reorder

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This commit is contained in:
Joe Bryan 2022-12-15 21:26:30 -05:00
parent 0901538df2
commit 8671d3091d
1 changed files with 10 additions and 1 deletions
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11
pkg/urbit/noun/manage.c
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@ -1003,10 +1003,19 @@ u3m_flog(c3_w gof_w)
void
u3m_water(u3_post* low_p, u3_post* hig_p)
{
// allow the segfault handler to fire before the road is set
//
// while not explicitly possible in the codebase,
// compiler optimizations can reorder stores
//
if ( !u3R ) {
*low_p = 0;
*hig_p = u3C.wor_i - 1;
}
// in a north road, hat points to the end of the heap + 1 word,
// while cap points to the top of the stack
//
if ( c3y == u3a_is_north(u3R) ) {
else if ( c3y == u3a_is_north(u3R) ) {
*low_p = u3R->hat_p - 1;
*hig_p = u3R->cap_p;
}