add a build variable to opt-out of some behaviors

Specifically behaviors that increase the chance that a wrapped program
will not behave like an unwrapped program does, thus causing
reliability issues.

2 files changed, 18 insertions, 0 deletions

diff --git a/src/Makefile b/src/Makefile
index 15e1c68..c1b890d 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -56,6 +56,17 @@
 #           -Dvariadic_promotion_t=int into CFLAGS).  See src/faketime_common.h for
 #           more info.
 #
+#     FAKE_STATELESS
+#         - Remove support for any functionality that requires sharing state across
+#           threads of a process, or different processes. This decreases the risk of
+#           interference with a program's normal execution, at the cost of supporting
+#           fewer ways of specifying the time.
+#           Concretely, this currently:
+#           - disables PTHREAD_SINGLETHREADED_TIME, which can cause deadlocks in
+#             multithreaded programs that fork due to making clock_gettime not
+#             async-signal-safe
+#           - disables all shared-memory across processes
+#
 #     FORCE_MONOTONIC_FIX
 #         - If the test program hangs forever on
 #                  " pthread_cond_timedwait: CLOCK_MONOTONIC test
diff --git a/src/libfaketime.c b/src/libfaketime.c
index afafc5d..6def8f2 100644
--- a/src/libfaketime.c
+++ b/src/libfaketime.c
@@ -60,6 +60,9 @@
 #include "time_ops.h"
 #include "faketime_common.h"
 
+#if defined PTHREAD_SINGLETHREADED_TIME && defined FAKE_STATELESS
+#undef PTHREAD_SINGLETHREADED_TIME
+#endif
 
 /* pthread-handling contributed by David North, TDI in version 0.7 */
 #if defined PTHREAD_SINGLETHREADED_TIME || defined FAKE_PTHREAD
@@ -2652,7 +2655,11 @@ static void ftpl_init(void)
 
   initialized = 1;
 
+#ifdef FAKE_STATELESS
+  if (0) ft_shm_init();
+#else
   ft_shm_init();
+#endif
 #ifdef FAKE_STAT
   if (getenv("NO_FAKE_STAT")!=NULL)
   {