bjoernager/rust
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sidestep potential over- and underflow in estimated stack bounds.

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See buildlog here for evidence of such occurring:
  http://buildbot.rust-lang.org/builders/auto-linux-32-opt/builds/3910/steps/test/logs/stdio
This commit is contained in:
Felix S. Klock II 2015-03-03 12:07:48 +01:00
parent 185c074798
commit 243c5164ea
1 changed files with 15 additions and 1 deletions
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16
src/libstd/rt/mod.rs
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@ -27,6 +27,7 @@ use marker::Send;
use ops::FnOnce; use ops::FnOnce;
use sys; use sys;
use thunk::Thunk; use thunk::Thunk;
use usize;
// Reexport some of our utilities which are expected by other crates. // Reexport some of our utilities which are expected by other crates.
pub use self::util::{default_sched_threads, min_stack, running_on_valgrind}; pub use self::util::{default_sched_threads, min_stack, running_on_valgrind};
@ -78,7 +79,20 @@ fn lang_start(main: *const u8, argc: int, argv: *const *const u8) -> int {
// FIXME #11359 we just assume that this thread has a stack of a // FIXME #11359 we just assume that this thread has a stack of a
// certain size, and estimate that there's at most 20KB of stack // certain size, and estimate that there's at most 20KB of stack
// frames above our current position. // frames above our current position.
let my_stack_bottom = my_stack_top + 20000 - OS_DEFAULT_STACK_ESTIMATE; const TWENTY_KB: uint = 20000;
// saturating-add to sidestep overflow
let top_plus_spill = if usize::MAX - TWENTY_KB < my_stack_top {
usize::MAX
} else {
my_stack_top + TWENTY_KB
};
// saturating-sub to sidestep underflow
let my_stack_bottom = if top_plus_spill < OS_DEFAULT_STACK_ESTIMATE {
0
} else {
top_plus_spill - OS_DEFAULT_STACK_ESTIMATE
};
let failed = unsafe { let failed = unsafe {
// First, make sure we don't trigger any __morestack overflow checks, // First, make sure we don't trigger any __morestack overflow checks,