http://llvm.org/bugs/show_bug.cgi?id=20546
Bug ID: 20546
Summary: atomic_compare_exchange_weak tests fail spuriously
Product: libc++
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
So far I've only seen this on ARM, but it looks like it's actually an error in
the tests rather than the implementation.
According to 29.6.5.25:
"Remark: A weak compare-and-exchange operation may fail spuriously. That is,
even when the contents of memory referred to by expected and object are equal,
it may return false and store back to expected the same memory contents that
were originally there. [ Note: This spurious failure enables implementation of
compare and-exchange on a broader class of machines, e.g., load-locked
store-conditional machines. A consequence of spurious failure is that nearly
all uses of weak compare-and-exchange will be in a loop"
Our tests have these calls used outside of a loop.
Two examples:
test/atomics/atomics.types.generic/integral.pass.cpp
test/atomics/atomics.types.operations/atomics.types.operations.req/atomic_compare_exchange_weak.pass.cpp
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
LLVMbugs mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs
