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Code Issues Releases Wiki Activity

ircd::ctx: Fix pointer punning in promise / shared_state.

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This commit is contained in:
Jason Volk 2018-07-06 00:23:50 -07:00
parent b0afbbb25e
commit da5d767431
1 changed files with 17 additions and 25 deletions
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42
include/ircd/ctx/shared_state.h
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@ -58,7 +58,11 @@ struct ircd::ctx::shared_state
using pointer_type = T *; using pointer_type = T *;
using reference_type = T &; using reference_type = T &;
promise<T> *p {nullptr}; union
{
promise<T> *p {nullptr};
future_state st;
};
T val; T val;
shared_state(promise<T> &p) shared_state(promise<T> &p)
@ -76,7 +80,11 @@ struct ircd::ctx::shared_state<void>
{ {
using value_type = void; using value_type = void;
promise<void> *p {nullptr}; union
{
promise<void> *p {nullptr};
future_state st;
};
shared_state(promise<void> &p) shared_state(promise<void> &p)
:p{&p} :p{&p}
@ -116,22 +124,17 @@ void
ircd::ctx::set(shared_state<T> &st, ircd::ctx::set(shared_state<T> &st,
const future_state &state) const future_state &state)
{ {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstrict-aliasing"
switch(state) switch(state)
{ {
case future_state::INVALID: assert(0); return; case future_state::INVALID: assert(0); return;
case future_state::PENDING: assert(0); return; case future_state::PENDING: assert(0); return;
case future_state::OBSERVED: case future_state::OBSERVED:
case future_state::READY: case future_state::READY:
reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x42);
return;
case future_state::RETRIEVED: case future_state::RETRIEVED:
reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x123); default:
st.st = state;
return; return;
} }
#pragma GCC diagnostic pop
} }
/// Internal use /// Internal use
@ -140,22 +143,17 @@ inline void
ircd::ctx::set(shared_state<void> &st, ircd::ctx::set(shared_state<void> &st,
const future_state &state) const future_state &state)
{ {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstrict-aliasing"
switch(state) switch(state)
{ {
case future_state::INVALID: assert(0); return; case future_state::INVALID: assert(0); return;
case future_state::PENDING: assert(0); return; case future_state::PENDING: assert(0); return;
case future_state::READY: case future_state::READY:
reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x42);
return;
case future_state::OBSERVED: case future_state::OBSERVED:
case future_state::RETRIEVED: case future_state::RETRIEVED:
reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x123); default:
st.st = state;
return; return;
} }
#pragma GCC diagnostic pop
} }
/// Internal; check if the current state is something; safe but unnecessary /// Internal; check if the current state is something; safe but unnecessary
@ -174,13 +172,7 @@ template<class T>
ircd::ctx::future_state ircd::ctx::future_state
ircd::ctx::state(const shared_state<T> &st) ircd::ctx::state(const shared_state<T> &st)
{ {
switch(uintptr_t(st.p)) return uintptr_t(st.p) >= 0x1000?
{ future_state::PENDING:
case 0x00: return future_state::INVALID; st.st;
case 0x42: return future_state::READY;
case 0x123: return future_state::RETRIEVED;
default:
assert(uintptr_t(st.p) >= 0x1000);
return future_state::PENDING;
}
} }