Fix handling of errno if external functions are invoked

If an external function in KLEE is invoked, it might update errno.
Previously, the errno specific variable in a state was only updated
if it was part of the executed instructions.
That opened up a timeframe that increased the likelihood of errno being
overwritten by another method call.

This patch fixes two issues:
* the errno of the KLEE process state is updated before the external
function call allowing to detect changes to it later on
* after the external call, the memory object of errno is directly
updated
with its new value, reducing the likelihood to be overwritten by
another
call

Additional features:
* Add support for `errno()` for Darwin as well.
* Simplified errno handling in POSIX layer

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/Core/SpecialFunctionHandler.h b/lib/Core/SpecialFunctionHandler.h
index 7e58018f..b11a4974 100644
--- a/lib/Core/SpecialFunctionHandler.h
+++ b/lib/Core/SpecialFunctionHandler.h
@@ -107,6 +107,7 @@ namespace klee {
     HANDLER(handleDelete);    
     HANDLER(handleDeleteArray);
     HANDLER(handleExit);
+    HANDLER(handleErrnoLocation);
     HANDLER(handleAliasFunction);
     HANDLER(handleFree);
     HANDLER(handleGetErrno);