java -Xmx8000000000 -Xss4m -jar ./plugins/org.eclipse.equinox.launcher_1.3.100.v20150511-1540.jar -data @noDefault -ultimatedata ./data -tc ../../../trunk/examples/toolchains/SifaC.xml -s ../../../trunk/examples/settings/default/automizer/svcomp-Reach-32bit-Automizer_Default.epf -i ../../../trunk/examples/svcomp/eca-rers2012/Problem04_label34.c -------------------------------------------------------------------------------- This is Ultimate 0.1.24-2989841 [2019-08-09 16:54:28,012 INFO L177 SettingsManager]: Resetting all preferences to default values... [2019-08-09 16:54:28,014 INFO L181 SettingsManager]: Resetting UltimateCore preferences to default values [2019-08-09 16:54:28,026 INFO L184 SettingsManager]: Ultimate Commandline Interface provides no preferences, ignoring... [2019-08-09 16:54:28,026 INFO L181 SettingsManager]: Resetting Boogie Preprocessor preferences to default values [2019-08-09 16:54:28,028 INFO L181 SettingsManager]: Resetting Boogie Procedure Inliner preferences to default values [2019-08-09 16:54:28,029 INFO L181 SettingsManager]: Resetting Abstract Interpretation preferences to default values [2019-08-09 16:54:28,031 INFO L181 SettingsManager]: Resetting LassoRanker preferences to default values [2019-08-09 16:54:28,033 INFO L181 SettingsManager]: Resetting Reaching Definitions preferences to default values [2019-08-09 16:54:28,033 INFO L181 SettingsManager]: Resetting SyntaxChecker preferences to default values [2019-08-09 16:54:28,035 INFO L181 SettingsManager]: Resetting Symbolic Interpretation preferences to default values [2019-08-09 16:54:28,036 INFO L184 SettingsManager]: Büchi Program Product provides no preferences, ignoring... [2019-08-09 16:54:28,036 INFO L181 SettingsManager]: Resetting LTL2Aut preferences to default values [2019-08-09 16:54:28,037 INFO L181 SettingsManager]: Resetting PEA to Boogie preferences to default values [2019-08-09 16:54:28,038 INFO L181 SettingsManager]: Resetting BlockEncodingV2 preferences to default values [2019-08-09 16:54:28,039 INFO L181 SettingsManager]: Resetting ChcToBoogie preferences to default values [2019-08-09 16:54:28,040 INFO L181 SettingsManager]: Resetting AutomataScriptInterpreter preferences to default values [2019-08-09 16:54:28,041 INFO L181 SettingsManager]: Resetting BuchiAutomizer preferences to default values [2019-08-09 16:54:28,043 INFO L181 SettingsManager]: Resetting CACSL2BoogieTranslator preferences to default values [2019-08-09 16:54:28,045 INFO L181 SettingsManager]: Resetting CodeCheck preferences to default values [2019-08-09 16:54:28,046 INFO L181 SettingsManager]: Resetting InvariantSynthesis preferences to default values [2019-08-09 16:54:28,048 INFO L181 SettingsManager]: Resetting RCFGBuilder preferences to default values [2019-08-09 16:54:28,049 INFO L181 SettingsManager]: Resetting Referee preferences to default values [2019-08-09 16:54:28,050 INFO L181 SettingsManager]: Resetting TraceAbstraction preferences to default values [2019-08-09 16:54:28,052 INFO L184 SettingsManager]: TraceAbstractionConcurrent provides no preferences, ignoring... [2019-08-09 16:54:28,052 INFO L184 SettingsManager]: TraceAbstractionWithAFAs provides no preferences, ignoring... [2019-08-09 16:54:28,052 INFO L181 SettingsManager]: Resetting TreeAutomizer preferences to default values [2019-08-09 16:54:28,053 INFO L181 SettingsManager]: Resetting IcfgToChc preferences to default values [2019-08-09 16:54:28,054 INFO L181 SettingsManager]: Resetting IcfgTransformer preferences to default values [2019-08-09 16:54:28,055 INFO L184 SettingsManager]: ReqToTest provides no preferences, ignoring... [2019-08-09 16:54:28,055 INFO L181 SettingsManager]: Resetting Boogie Printer preferences to default values [2019-08-09 16:54:28,056 INFO L181 SettingsManager]: Resetting ChcSmtPrinter preferences to default values [2019-08-09 16:54:28,057 INFO L181 SettingsManager]: Resetting ReqPrinter preferences to default values [2019-08-09 16:54:28,057 INFO L181 SettingsManager]: Resetting Witness Printer preferences to default values [2019-08-09 16:54:28,058 INFO L184 SettingsManager]: Boogie PL CUP Parser provides no preferences, ignoring... [2019-08-09 16:54:28,059 INFO L181 SettingsManager]: Resetting CDTParser preferences to default values [2019-08-09 16:54:28,059 INFO L184 SettingsManager]: AutomataScriptParser provides no preferences, ignoring... [2019-08-09 16:54:28,060 INFO L184 SettingsManager]: ReqParser provides no preferences, ignoring... [2019-08-09 16:54:28,060 INFO L181 SettingsManager]: Resetting SmtParser preferences to default values [2019-08-09 16:54:28,061 INFO L181 SettingsManager]: Resetting Witness Parser preferences to default values [2019-08-09 16:54:28,061 INFO L188 SettingsManager]: Finished resetting all preferences to default values... [2019-08-09 16:54:28,063 INFO L101 SettingsManager]: Beginning loading settings from /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/settings/default/automizer/svcomp-Reach-32bit-Automizer_Default.epf [2019-08-09 16:54:28,092 INFO L113 SettingsManager]: Loading preferences was successful [2019-08-09 16:54:28,092 INFO L115 SettingsManager]: Preferences different from defaults after loading the file: [2019-08-09 16:54:28,094 INFO L136 SettingsManager]: Preferences of BlockEncodingV2 differ from their defaults: [2019-08-09 16:54:28,094 INFO L138 SettingsManager]: * Create parallel compositions if possible=false [2019-08-09 16:54:28,095 INFO L138 SettingsManager]: * Use SBE=true [2019-08-09 16:54:28,095 INFO L136 SettingsManager]: Preferences of CACSL2BoogieTranslator differ from their defaults: [2019-08-09 16:54:28,095 INFO L138 SettingsManager]: * sizeof long=4 [2019-08-09 16:54:28,095 INFO L138 SettingsManager]: * Overapproximate operations on floating types=true [2019-08-09 16:54:28,095 INFO L138 SettingsManager]: * sizeof POINTER=4 [2019-08-09 16:54:28,096 INFO L138 SettingsManager]: * Check division by zero=IGNORE [2019-08-09 16:54:28,096 INFO L138 SettingsManager]: * Pointer to allocated memory at dereference=IGNORE [2019-08-09 16:54:28,096 INFO L138 SettingsManager]: * If two pointers are subtracted or compared they have the same base address=IGNORE [2019-08-09 16:54:28,097 INFO L138 SettingsManager]: * Check array bounds for arrays that are off heap=IGNORE [2019-08-09 16:54:28,097 INFO L138 SettingsManager]: * sizeof long double=12 [2019-08-09 16:54:28,097 INFO L138 SettingsManager]: * Check if freed pointer was valid=false [2019-08-09 16:54:28,098 INFO L138 SettingsManager]: * Use constant arrays=true [2019-08-09 16:54:28,098 INFO L138 SettingsManager]: * Pointer base address is valid at dereference=IGNORE [2019-08-09 16:54:28,099 INFO L136 SettingsManager]: Preferences of RCFGBuilder differ from their defaults: [2019-08-09 16:54:28,099 INFO L138 SettingsManager]: * Size of a code block=SequenceOfStatements [2019-08-09 16:54:28,099 INFO L138 SettingsManager]: * To the following directory=./dump/ [2019-08-09 16:54:28,100 INFO L138 SettingsManager]: * SMT solver=External_DefaultMode [2019-08-09 16:54:28,100 INFO L138 SettingsManager]: * Command for external solver=z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:2000 [2019-08-09 16:54:28,100 INFO L136 SettingsManager]: Preferences of TraceAbstraction differ from their defaults: [2019-08-09 16:54:28,100 INFO L138 SettingsManager]: * Compute Interpolants along a Counterexample=FPandBP [2019-08-09 16:54:28,101 INFO L138 SettingsManager]: * Positions where we compute the Hoare Annotation=LoopsAndPotentialCycles [2019-08-09 16:54:28,101 INFO L138 SettingsManager]: * Trace refinement strategy=CAMEL [2019-08-09 16:54:28,101 INFO L138 SettingsManager]: * SMT solver=External_ModelsAndUnsatCoreMode [2019-08-09 16:54:28,101 INFO L138 SettingsManager]: * Command for external solver=z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in [2019-08-09 16:54:28,102 INFO L138 SettingsManager]: * Compute Hoare Annotation of negated interpolant automaton, abstraction and CFG=true [2019-08-09 16:54:28,147 INFO L81 nceAwareModelManager]: Repository-Root is: /tmp [2019-08-09 16:54:28,160 INFO L258 ainManager$Toolchain]: [Toolchain 1]: Applicable parser(s) successfully (re)initialized [2019-08-09 16:54:28,164 INFO L214 ainManager$Toolchain]: [Toolchain 1]: Toolchain selected. [2019-08-09 16:54:28,165 INFO L271 PluginConnector]: Initializing CDTParser... [2019-08-09 16:54:28,166 INFO L275 PluginConnector]: CDTParser initialized [2019-08-09 16:54:28,166 INFO L428 ainManager$Toolchain]: [Toolchain 1]: Parsing single file: /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/svcomp/eca-rers2012/Problem04_label34.c [2019-08-09 16:54:28,229 INFO L220 CDTParser]: Created temporary CDT project at /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/2f894ff95/d661a645490640cba46163758e94a89d/FLAGa00b27b07 [2019-08-09 16:54:29,043 INFO L306 CDTParser]: Found 1 translation units. [2019-08-09 16:54:29,046 INFO L160 CDTParser]: Scanning /storage/repos/ultimate/trunk/examples/svcomp/eca-rers2012/Problem04_label34.c [2019-08-09 16:54:29,085 INFO L349 CDTParser]: About to delete temporary CDT project at /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/2f894ff95/d661a645490640cba46163758e94a89d/FLAGa00b27b07 [2019-08-09 16:54:29,564 INFO L357 CDTParser]: Successfully deleted /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/2f894ff95/d661a645490640cba46163758e94a89d [2019-08-09 16:54:29,574 INFO L296 ainManager$Toolchain]: ####################### [Toolchain 1] ####################### [2019-08-09 16:54:29,576 INFO L131 ToolchainWalker]: Walking toolchain with 4 elements. [2019-08-09 16:54:29,577 INFO L113 PluginConnector]: ------------------------CACSL2BoogieTranslator---------------------------- [2019-08-09 16:54:29,577 INFO L271 PluginConnector]: Initializing CACSL2BoogieTranslator... [2019-08-09 16:54:29,581 INFO L275 PluginConnector]: CACSL2BoogieTranslator initialized [2019-08-09 16:54:29,582 INFO L185 PluginConnector]: Executing the observer ACSLObjectContainerObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 09.08 04:54:29" (1/1) ... [2019-08-09 16:54:29,586 INFO L205 PluginConnector]: Invalid model from CACSL2BoogieTranslator for observer de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator.ACSLObjectContainerObserver@5231554b and model type de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:29, skipping insertion in model container [2019-08-09 16:54:29,587 INFO L185 PluginConnector]: Executing the observer CACSL2BoogieTranslatorObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 09.08 04:54:29" (1/1) ... [2019-08-09 16:54:29,595 INFO L142 MainTranslator]: Starting translation in SV-COMP mode [2019-08-09 16:54:29,770 INFO L173 MainTranslator]: Built tables and reachable declarations [2019-08-09 16:54:31,725 INFO L206 PostProcessor]: Analyzing one entry point: main [2019-08-09 16:54:31,734 INFO L188 MainTranslator]: Completed pre-run [2019-08-09 16:54:32,570 INFO L206 PostProcessor]: Analyzing one entry point: main [2019-08-09 16:54:32,627 INFO L192 MainTranslator]: Completed translation [2019-08-09 16:54:32,628 INFO L202 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32 WrapperNode [2019-08-09 16:54:32,628 INFO L132 PluginConnector]: ------------------------ END CACSL2BoogieTranslator---------------------------- [2019-08-09 16:54:32,629 INFO L113 PluginConnector]: ------------------------Boogie Preprocessor---------------------------- [2019-08-09 16:54:32,630 INFO L271 PluginConnector]: Initializing Boogie Preprocessor... [2019-08-09 16:54:32,630 INFO L275 PluginConnector]: Boogie Preprocessor initialized [2019-08-09 16:54:32,647 INFO L185 PluginConnector]: Executing the observer EnsureBoogieModelObserver from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,648 INFO L185 PluginConnector]: Executing the observer TypeChecker from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,708 INFO L185 PluginConnector]: Executing the observer ConstExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,708 INFO L185 PluginConnector]: Executing the observer StructExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,799 INFO L185 PluginConnector]: Executing the observer UnstructureCode from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,831 INFO L185 PluginConnector]: Executing the observer FunctionInliner from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,856 INFO L185 PluginConnector]: Executing the observer BoogieSymbolTableConstructor from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... [2019-08-09 16:54:32,881 INFO L132 PluginConnector]: ------------------------ END Boogie Preprocessor---------------------------- [2019-08-09 16:54:32,881 INFO L113 PluginConnector]: ------------------------RCFGBuilder---------------------------- [2019-08-09 16:54:32,882 INFO L271 PluginConnector]: Initializing RCFGBuilder... [2019-08-09 16:54:32,882 INFO L275 PluginConnector]: RCFGBuilder initialized [2019-08-09 16:54:32,883 INFO L185 PluginConnector]: Executing the observer RCFGBuilderObserver from plugin RCFGBuilder for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 09.08 04:54:32" (1/1) ... No working directory specified, using /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 Starting monitored process 1 with z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:2000 (exit command is (exit), workingDir is null) Waiting until toolchain timeout for monitored process 1 with z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:2000 [2019-08-09 16:54:32,958 INFO L138 BoogieDeclarations]: Found implementation of procedure ULTIMATE.init [2019-08-09 16:54:32,959 INFO L138 BoogieDeclarations]: Found implementation of procedure ULTIMATE.start [2019-08-09 16:54:32,959 INFO L138 BoogieDeclarations]: Found implementation of procedure calculate_output [2019-08-09 16:54:32,959 INFO L138 BoogieDeclarations]: Found implementation of procedure calculate_output2 [2019-08-09 16:54:32,959 INFO L138 BoogieDeclarations]: Found implementation of procedure calculate_output3 [2019-08-09 16:54:32,960 INFO L138 BoogieDeclarations]: Found implementation of procedure calculate_output4 [2019-08-09 16:54:32,960 INFO L138 BoogieDeclarations]: Found implementation of procedure main [2019-08-09 16:54:32,960 INFO L130 BoogieDeclarations]: Found specification of procedure calculate_output [2019-08-09 16:54:32,960 INFO L130 BoogieDeclarations]: Found specification of procedure calculate_output2 [2019-08-09 16:54:32,960 INFO L130 BoogieDeclarations]: Found specification of procedure calculate_output3 [2019-08-09 16:54:32,961 INFO L130 BoogieDeclarations]: Found specification of procedure calculate_output4 [2019-08-09 16:54:32,961 INFO L130 BoogieDeclarations]: Found specification of procedure __VERIFIER_error [2019-08-09 16:54:32,961 INFO L130 BoogieDeclarations]: Found specification of procedure __VERIFIER_nondet_int [2019-08-09 16:54:32,961 INFO L130 BoogieDeclarations]: Found specification of procedure exit [2019-08-09 16:54:32,961 INFO L130 BoogieDeclarations]: Found specification of procedure main [2019-08-09 16:54:32,962 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.init [2019-08-09 16:54:32,962 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.start [2019-08-09 16:54:37,395 INFO L278 CfgBuilder]: Using the 1 location(s) as analysis (start of procedure ULTIMATE.start) [2019-08-09 16:54:37,399 INFO L283 CfgBuilder]: Removed 1 assume(true) statements. [2019-08-09 16:54:37,402 INFO L202 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 09.08 04:54:37 BoogieIcfgContainer [2019-08-09 16:54:37,402 INFO L132 PluginConnector]: ------------------------ END RCFGBuilder---------------------------- [2019-08-09 16:54:37,402 INFO L113 PluginConnector]: ------------------------Symbolic Interpretation---------------------------- [2019-08-09 16:54:37,403 INFO L271 PluginConnector]: Initializing Symbolic Interpretation... [2019-08-09 16:54:37,403 INFO L275 PluginConnector]: Symbolic Interpretation initialized [2019-08-09 16:54:37,404 INFO L185 PluginConnector]: Executing the observer SymbolicInterpretationObserver from plugin Symbolic Interpretation for "de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 09.08 04:54:37" (1/1) ... [2019-08-09 16:54:41,570 WARN L88 terpretationObserver]: Some locations of interest might be reachable, see reported results. [2019-08-09 16:54:41,579 INFO L132 PluginConnector]: ------------------------ END Symbolic Interpretation---------------------------- [2019-08-09 16:54:41,586 INFO L168 Benchmark]: Toolchain (without parser) took 12005.24 ms. Allocated memory was 138.4 MB in the beginning and 596.1 MB in the end (delta: 457.7 MB). Free memory was 72.9 MB in the beginning and 509.4 MB in the end (delta: -436.5 MB). Peak memory consumption was 410.8 MB. Max. memory is 7.1 GB. [2019-08-09 16:54:41,591 INFO L168 Benchmark]: CDTParser took 0.23 ms. Allocated memory is still 138.4 MB. Free memory was 106.2 MB in the beginning and 106.0 MB in the end (delta: 212.8 kB). Peak memory consumption was 212.8 kB. Max. memory is 7.1 GB. [2019-08-09 16:54:41,592 INFO L168 Benchmark]: CACSL2BoogieTranslator took 3051.69 ms. Allocated memory was 138.4 MB in the beginning and 265.3 MB in the end (delta: 126.9 MB). Free memory was 72.5 MB in the beginning and 202.0 MB in the end (delta: -129.6 MB). Peak memory consumption was 107.9 MB. Max. memory is 7.1 GB. [2019-08-09 16:54:41,593 INFO L168 Benchmark]: Boogie Preprocessor took 251.77 ms. Allocated memory is still 265.3 MB. Free memory was 202.0 MB in the beginning and 172.7 MB in the end (delta: 29.3 MB). Peak memory consumption was 29.3 MB. Max. memory is 7.1 GB. [2019-08-09 16:54:41,596 INFO L168 Benchmark]: RCFGBuilder took 4520.53 ms. Allocated memory was 265.3 MB in the beginning and 429.9 MB in the end (delta: 164.6 MB). Free memory was 172.7 MB in the beginning and 328.1 MB in the end (delta: -155.4 MB). Peak memory consumption was 211.4 MB. Max. memory is 7.1 GB. [2019-08-09 16:54:41,597 INFO L168 Benchmark]: Symbolic Interpretation took 4176.96 ms. Allocated memory was 429.9 MB in the beginning and 596.1 MB in the end (delta: 166.2 MB). Free memory was 328.1 MB in the beginning and 509.4 MB in the end (delta: -181.3 MB). Peak memory consumption was 374.5 MB. Max. memory is 7.1 GB. [2019-08-09 16:54:41,608 INFO L335 ainManager$Toolchain]: ####################### End [Toolchain 1] ####################### --- Results --- * Results from de.uni_freiburg.informatik.ultimate.plugins.symbolicinterpretation: - UnprovableResult [Line: 4721]: Unable to prove that call of __VERIFIER_error() unreachable Unable to prove that call of __VERIFIER_error() unreachable Reason: Interpreter reached this location of interest. Location might be reachable. Predicate is 67434#(and (= 1 ~a1~0) (= ~a28~0 16) (= ~a26~0 19) (= 1 ~a3~0) (= ~a14~0 20) (not (= 1 ~a7~0)) (= ~a25~0 1) (= 16 ~a4~0)). Possible FailurePath: * Results from de.uni_freiburg.informatik.ultimate.core: - StatisticsResult: Toolchain Benchmarks Benchmark results are: * CDTParser took 0.23 ms. Allocated memory is still 138.4 MB. Free memory was 106.2 MB in the beginning and 106.0 MB in the end (delta: 212.8 kB). Peak memory consumption was 212.8 kB. Max. memory is 7.1 GB. * CACSL2BoogieTranslator took 3051.69 ms. Allocated memory was 138.4 MB in the beginning and 265.3 MB in the end (delta: 126.9 MB). Free memory was 72.5 MB in the beginning and 202.0 MB in the end (delta: -129.6 MB). Peak memory consumption was 107.9 MB. Max. memory is 7.1 GB. * Boogie Preprocessor took 251.77 ms. Allocated memory is still 265.3 MB. Free memory was 202.0 MB in the beginning and 172.7 MB in the end (delta: 29.3 MB). Peak memory consumption was 29.3 MB. Max. memory is 7.1 GB. * RCFGBuilder took 4520.53 ms. Allocated memory was 265.3 MB in the beginning and 429.9 MB in the end (delta: 164.6 MB). Free memory was 172.7 MB in the beginning and 328.1 MB in the end (delta: -155.4 MB). Peak memory consumption was 211.4 MB. Max. memory is 7.1 GB. * Symbolic Interpretation took 4176.96 ms. Allocated memory was 429.9 MB in the beginning and 596.1 MB in the end (delta: 166.2 MB). Free memory was 328.1 MB in the beginning and 509.4 MB in the end (delta: -181.3 MB). Peak memory consumption was 374.5 MB. Max. memory is 7.1 GB. RESULT: Ultimate could not prove your program: unable to determine feasibility of some traces Received shutdown request...