Improved comment on the sqlite3FaultSim() function. No changes to code.

FossilOrigin-Name: 08b29672c552e5a6a3874746c6cc7025295e0e44dec43a1bfba3022acce849ff

manifest

@@ -1,5 +1,5 @@
-C In\sthe\stest_vfs.c\sVFS,\sif\sa\sTcl\sxWrite\sscript\sreturns\s"SQLITE_OMIT",\ssilently\somit\sthe\swrite()\scall.
-D 2019-04-05T16:52:45.185
+C Improved\scomment\son\sthe\ssqlite3FaultSim()\sfunction.\s\sNo\schanges\sto\scode.
+D 2019-04-05T17:22:50.419
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -587,7 +587,7 @@ F src/trigger.c bb034c08eca111e66a19cda045903a12547c1be2294b5570d794b869d9c44a73
 F src/update.c 0b973357d88092140531e07ff641139c26fb4380b0b9f5ed98c5f7691b4604d1
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 F src/utf.c 810fbfebe12359f10bc2a011520a6e10879ab2a163bcb26c74768eab82ea62a5
-F src/util.c 82a2e3f691a3b654be872e305dab1f455e565dedf5e6a90c818c1ab307c00432
+F src/util.c 276d937c78e9d06f84db469d394573a5c533fb8d0e11a5114c575a99f3dabfa5
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 F src/vdbe.h 712bca562eaed1c25506b9faf9680bdc75fc42e2f4a1cd518d883fa79c7a4237
@@ -1815,7 +1815,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
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manifest.uuid

@@ -1 +1 @@
-8b5a621e2ee3bb9d7d4f905217872e7e59153be9477aaa626cea287d56710b5b
+08b29672c552e5a6a3874746c6cc7025295e0e44dec43a1bfba3022acce849ff

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){