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-rw-r--r--src/util.c22
1 files changed, 15 insertions, 7 deletions
diff --git a/src/util.c b/src/util.c
index 8432d897f..1d8699846 100644
--- a/src/util.c
+++ b/src/util.c
@@ -32,15 +32,23 @@ void sqlite3Coverage(int x){
#endif
/*
-** Give a callback to the test harness that can be used to simulate faults
-** in places where it is difficult or expensive to do so purely by means
-** of inputs.
+** Calls to sqlite3FaultSim() are used to simulate a failure during testing,
+** or to bypass normal error detection during testing in order to let
+** execute proceed futher downstream.
**
-** The intent of the integer argument is to let the fault simulator know
-** which of multiple sqlite3FaultSim() calls has been hit.
+** In deployment, sqlite3FaultSim() *always* return SQLITE_OK (0). The
+** sqlite3FaultSim() function only returns non-zero during testing.
**
-** Return whatever integer value the test callback returns, or return
-** SQLITE_OK if no test callback is installed.
+** During testing, if the test harness has set a fault-sim callback using
+** a call to sqlite3_test_control(SQLITE_TESTCTRL_FAULT_INSTALL), then
+** each call to sqlite3FaultSim() is relayed to that application-supplied
+** callback and the integer return value form the application-supplied
+** callback is returned by sqlite3FaultSim().
+**
+** The integer argument to sqlite3FaultSim() is a code to identify which
+** sqlite3FaultSim() instance is being invoked. Each call to sqlite3FaultSim()
+** should have a unique code. To prevent legacy testing applications from
+** breaking, the codes should not be changed or reused.
*/
#ifndef SQLITE_UNTESTABLE
int sqlite3FaultSim(int iTest){