add C11 thread creation and related thread functions
based on patch by Jens Gustedt.
the main difficulty here is handling the difference between start
function signatures and thread return types for C11 threads versus
POSIX threads. pointers to void are assumed to be able to represent
faithfully all values of int. the function pointer for the thread
start function is cast to an incorrect type for passing through
pthread_create, but is cast back to its correct type before calling so
that the behavior of the call is well-defined.
changes to the existing threads implementation were kept minimal to
reduce the risk of regressions, and duplication of code that carries
implementation-specific assumptions was avoided for ease and safety of
future maintenance.
diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
index 74c62cc..ae6e60b 100644
--- a/src/internal/pthread_impl.h
+++ b/src/internal/pthread_impl.h
@@ -128,4 +128,6 @@
#define DEFAULT_STACK_SIZE 81920
#define DEFAULT_GUARD_SIZE PAGE_SIZE
+#define __ATTRP_C11_THREAD ((void*)(uintptr_t)-1)
+
#endif