java -Xmx8000000000 -Xss4m -jar ./plugins/org.eclipse.equinox.launcher_1.3.100.v20150511-1540.jar -data @noDefault -ultimatedata ./data -tc ../../../trunk/examples/toolchains/AbstractInterpretationC.xml -s ../../../trunk/examples/settings/ai/svcomp-Reach-32bit-Automizer_Default+AIv2_INT.epf -i ../../../trunk/examples/svcomp/ldv-regression/oomInt.i -------------------------------------------------------------------------------- This is Ultimate 0.1.24-673a906-m [2019-10-03 12:34:47,027 INFO L177 SettingsManager]: Resetting all preferences to default values... [2019-10-03 12:34:47,032 INFO L181 SettingsManager]: Resetting UltimateCore preferences to default values [2019-10-03 12:34:47,047 INFO L184 SettingsManager]: Ultimate Commandline Interface provides no preferences, ignoring... [2019-10-03 12:34:47,048 INFO L181 SettingsManager]: Resetting Boogie Preprocessor preferences to default values [2019-10-03 12:34:47,049 INFO L181 SettingsManager]: Resetting Boogie Procedure Inliner preferences to default values [2019-10-03 12:34:47,050 INFO L181 SettingsManager]: Resetting Abstract Interpretation preferences to default values [2019-10-03 12:34:47,052 INFO L181 SettingsManager]: Resetting LassoRanker preferences to default values [2019-10-03 12:34:47,054 INFO L181 SettingsManager]: Resetting Reaching Definitions preferences to default values [2019-10-03 12:34:47,055 INFO L181 SettingsManager]: Resetting SyntaxChecker preferences to default values [2019-10-03 12:34:47,056 INFO L181 SettingsManager]: Resetting Sifa preferences to default values [2019-10-03 12:34:47,057 INFO L184 SettingsManager]: Büchi Program Product provides no preferences, ignoring... [2019-10-03 12:34:47,057 INFO L181 SettingsManager]: Resetting LTL2Aut preferences to default values [2019-10-03 12:34:47,058 INFO L181 SettingsManager]: Resetting PEA to Boogie preferences to default values [2019-10-03 12:34:47,059 INFO L181 SettingsManager]: Resetting BlockEncodingV2 preferences to default values [2019-10-03 12:34:47,060 INFO L181 SettingsManager]: Resetting ChcToBoogie preferences to default values [2019-10-03 12:34:47,061 INFO L181 SettingsManager]: Resetting AutomataScriptInterpreter preferences to default values [2019-10-03 12:34:47,062 INFO L181 SettingsManager]: Resetting BuchiAutomizer preferences to default values [2019-10-03 12:34:47,064 INFO L181 SettingsManager]: Resetting CACSL2BoogieTranslator preferences to default values [2019-10-03 12:34:47,066 INFO L181 SettingsManager]: Resetting CodeCheck preferences to default values [2019-10-03 12:34:47,068 INFO L181 SettingsManager]: Resetting InvariantSynthesis preferences to default values [2019-10-03 12:34:47,069 INFO L181 SettingsManager]: Resetting RCFGBuilder preferences to default values [2019-10-03 12:34:47,070 INFO L181 SettingsManager]: Resetting Referee preferences to default values [2019-10-03 12:34:47,071 INFO L181 SettingsManager]: Resetting TraceAbstraction preferences to default values [2019-10-03 12:34:47,074 INFO L184 SettingsManager]: TraceAbstractionConcurrent provides no preferences, ignoring... [2019-10-03 12:34:47,075 INFO L184 SettingsManager]: TraceAbstractionWithAFAs provides no preferences, ignoring... [2019-10-03 12:34:47,075 INFO L181 SettingsManager]: Resetting TreeAutomizer preferences to default values [2019-10-03 12:34:47,077 INFO L181 SettingsManager]: Resetting IcfgToChc preferences to default values [2019-10-03 12:34:47,078 INFO L181 SettingsManager]: Resetting IcfgTransformer preferences to default values [2019-10-03 12:34:47,080 INFO L184 SettingsManager]: ReqToTest provides no preferences, ignoring... [2019-10-03 12:34:47,081 INFO L181 SettingsManager]: Resetting Boogie Printer preferences to default values [2019-10-03 12:34:47,082 INFO L181 SettingsManager]: Resetting ChcSmtPrinter preferences to default values [2019-10-03 12:34:47,082 INFO L181 SettingsManager]: Resetting ReqPrinter preferences to default values [2019-10-03 12:34:47,083 INFO L181 SettingsManager]: Resetting Witness Printer preferences to default values [2019-10-03 12:34:47,084 INFO L184 SettingsManager]: Boogie PL CUP Parser provides no preferences, ignoring... [2019-10-03 12:34:47,085 INFO L181 SettingsManager]: Resetting CDTParser preferences to default values [2019-10-03 12:34:47,085 INFO L184 SettingsManager]: AutomataScriptParser provides no preferences, ignoring... [2019-10-03 12:34:47,086 INFO L184 SettingsManager]: ReqParser provides no preferences, ignoring... [2019-10-03 12:34:47,086 INFO L181 SettingsManager]: Resetting SmtParser preferences to default values [2019-10-03 12:34:47,087 INFO L181 SettingsManager]: Resetting Witness Parser preferences to default values [2019-10-03 12:34:47,088 INFO L188 SettingsManager]: Finished resetting all preferences to default values... [2019-10-03 12:34:47,088 INFO L101 SettingsManager]: Beginning loading settings from /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/settings/ai/svcomp-Reach-32bit-Automizer_Default+AIv2_INT.epf [2019-10-03 12:34:47,111 INFO L113 SettingsManager]: Loading preferences was successful [2019-10-03 12:34:47,111 INFO L115 SettingsManager]: Preferences different from defaults after loading the file: [2019-10-03 12:34:47,112 INFO L136 SettingsManager]: Preferences of UltimateCore differ from their defaults: [2019-10-03 12:34:47,112 INFO L138 SettingsManager]: * Log level for plugins=info [2019-10-03 12:34:47,113 INFO L136 SettingsManager]: Preferences of Boogie Procedure Inliner differ from their defaults: [2019-10-03 12:34:47,113 INFO L138 SettingsManager]: * User list type=DISABLED [2019-10-03 12:34:47,114 INFO L138 SettingsManager]: * Ignore calls to and inside polymorphic procedures=false [2019-10-03 12:34:47,114 INFO L138 SettingsManager]: * Ignore calls to recursive procedures=false [2019-10-03 12:34:47,114 INFO L136 SettingsManager]: Preferences of Abstract Interpretation differ from their defaults: [2019-10-03 12:34:47,114 INFO L138 SettingsManager]: * Abstract domain=IntervalDomain [2019-10-03 12:34:47,115 INFO L136 SettingsManager]: Preferences of CACSL2BoogieTranslator differ from their defaults: [2019-10-03 12:34:47,115 INFO L138 SettingsManager]: * sizeof long=4 [2019-10-03 12:34:47,116 INFO L138 SettingsManager]: * sizeof POINTER=4 [2019-10-03 12:34:47,116 INFO L138 SettingsManager]: * Check division by zero=IGNORE [2019-10-03 12:34:47,116 INFO L138 SettingsManager]: * Pointer to allocated memory at dereference=IGNORE [2019-10-03 12:34:47,117 INFO L138 SettingsManager]: * If two pointers are subtracted or compared they have the same base address=IGNORE [2019-10-03 12:34:47,117 INFO L138 SettingsManager]: * Check array bounds for arrays that are off heap=IGNORE [2019-10-03 12:34:47,118 INFO L138 SettingsManager]: * sizeof long double=12 [2019-10-03 12:34:47,118 INFO L138 SettingsManager]: * Check if freed pointer was valid=false [2019-10-03 12:34:47,118 INFO L138 SettingsManager]: * Pointer base address is valid at dereference=IGNORE [2019-10-03 12:34:47,119 INFO L136 SettingsManager]: Preferences of RCFGBuilder differ from their defaults: [2019-10-03 12:34:47,119 INFO L138 SettingsManager]: * Remove goto edges from RCFG=true [2019-10-03 12:34:47,119 INFO L138 SettingsManager]: * Size of a code block=SequenceOfStatements [2019-10-03 12:34:47,119 INFO L138 SettingsManager]: * Command for external solver=z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:2000 [2019-10-03 12:34:47,120 INFO L136 SettingsManager]: Preferences of TraceAbstraction differ from their defaults: [2019-10-03 12:34:47,120 INFO L138 SettingsManager]: * Compute Interpolants along a Counterexample=FPandBP [2019-10-03 12:34:47,120 INFO L138 SettingsManager]: * Trace refinement strategy=TAIPAN [2019-10-03 12:34:47,120 INFO L138 SettingsManager]: * Command for external solver=z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in [2019-10-03 12:34:47,120 INFO L138 SettingsManager]: * SMT solver=External_ModelsAndUnsatCoreMode [2019-10-03 12:34:47,121 INFO L138 SettingsManager]: * Abstract interpretation Mode=USE_PREDICATES [2019-10-03 12:34:47,178 INFO L81 nceAwareModelManager]: Repository-Root is: /tmp [2019-10-03 12:34:47,200 INFO L258 ainManager$Toolchain]: [Toolchain 1]: Applicable parser(s) successfully (re)initialized [2019-10-03 12:34:47,205 INFO L214 ainManager$Toolchain]: [Toolchain 1]: Toolchain selected. [2019-10-03 12:34:47,207 INFO L271 PluginConnector]: Initializing CDTParser... [2019-10-03 12:34:47,207 INFO L275 PluginConnector]: CDTParser initialized [2019-10-03 12:34:47,208 INFO L428 ainManager$Toolchain]: [Toolchain 1]: Parsing single file: /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/svcomp/ldv-regression/oomInt.i [2019-10-03 12:34:47,272 INFO L220 CDTParser]: Created temporary CDT project at /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/100958ccc/3e7c1cdcef2742949b91198fadbfdb04/FLAG3cb34a7a2 [2019-10-03 12:34:47,728 INFO L306 CDTParser]: Found 1 translation units. [2019-10-03 12:34:47,729 INFO L160 CDTParser]: Scanning /storage/repos/ultimate/trunk/examples/svcomp/ldv-regression/oomInt.i [2019-10-03 12:34:47,735 INFO L349 CDTParser]: About to delete temporary CDT project at /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/100958ccc/3e7c1cdcef2742949b91198fadbfdb04/FLAG3cb34a7a2 [2019-10-03 12:34:48,119 INFO L357 CDTParser]: Successfully deleted /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/100958ccc/3e7c1cdcef2742949b91198fadbfdb04 [2019-10-03 12:34:48,131 INFO L296 ainManager$Toolchain]: ####################### [Toolchain 1] ####################### [2019-10-03 12:34:48,133 INFO L131 ToolchainWalker]: Walking toolchain with 4 elements. [2019-10-03 12:34:48,136 INFO L113 PluginConnector]: ------------------------CACSL2BoogieTranslator---------------------------- [2019-10-03 12:34:48,137 INFO L271 PluginConnector]: Initializing CACSL2BoogieTranslator... [2019-10-03 12:34:48,140 INFO L275 PluginConnector]: CACSL2BoogieTranslator initialized [2019-10-03 12:34:48,141 INFO L185 PluginConnector]: Executing the observer ACSLObjectContainerObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,144 INFO L205 PluginConnector]: Invalid model from CACSL2BoogieTranslator for observer de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator.ACSLObjectContainerObserver@7609cfe5 and model type de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48, skipping insertion in model container [2019-10-03 12:34:48,145 INFO L185 PluginConnector]: Executing the observer CACSL2BoogieTranslatorObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,153 INFO L142 MainTranslator]: Starting translation in SV-COMP mode [2019-10-03 12:34:48,173 INFO L173 MainTranslator]: Built tables and reachable declarations [2019-10-03 12:34:48,391 INFO L206 PostProcessor]: Analyzing one entry point: main [2019-10-03 12:34:48,396 INFO L188 MainTranslator]: Completed pre-run [2019-10-03 12:34:48,408 INFO L206 PostProcessor]: Analyzing one entry point: main [2019-10-03 12:34:48,421 INFO L192 MainTranslator]: Completed translation [2019-10-03 12:34:48,421 INFO L202 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48 WrapperNode [2019-10-03 12:34:48,422 INFO L132 PluginConnector]: ------------------------ END CACSL2BoogieTranslator---------------------------- [2019-10-03 12:34:48,422 INFO L113 PluginConnector]: ------------------------Boogie Preprocessor---------------------------- [2019-10-03 12:34:48,422 INFO L271 PluginConnector]: Initializing Boogie Preprocessor... [2019-10-03 12:34:48,422 INFO L275 PluginConnector]: Boogie Preprocessor initialized [2019-10-03 12:34:48,524 INFO L185 PluginConnector]: Executing the observer EnsureBoogieModelObserver from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,526 INFO L185 PluginConnector]: Executing the observer TypeChecker from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,532 INFO L185 PluginConnector]: Executing the observer ConstExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,533 INFO L185 PluginConnector]: Executing the observer StructExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,537 INFO L185 PluginConnector]: Executing the observer UnstructureCode from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,538 INFO L185 PluginConnector]: Executing the observer FunctionInliner from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,539 INFO L185 PluginConnector]: Executing the observer BoogieSymbolTableConstructor from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,541 INFO L132 PluginConnector]: ------------------------ END Boogie Preprocessor---------------------------- [2019-10-03 12:34:48,541 INFO L113 PluginConnector]: ------------------------RCFGBuilder---------------------------- [2019-10-03 12:34:48,541 INFO L271 PluginConnector]: Initializing RCFGBuilder... [2019-10-03 12:34:48,541 INFO L275 PluginConnector]: RCFGBuilder initialized [2019-10-03 12:34:48,542 INFO L185 PluginConnector]: Executing the observer RCFGBuilderObserver from plugin RCFGBuilder for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.10 12:34:48" (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 [2019-10-03 12:34:48,599 INFO L138 BoogieDeclarations]: Found implementation of procedure ULTIMATE.init [2019-10-03 12:34:48,599 INFO L138 BoogieDeclarations]: Found implementation of procedure ULTIMATE.start [2019-10-03 12:34:48,599 INFO L138 BoogieDeclarations]: Found implementation of procedure __VERIFIER_assert [2019-10-03 12:34:48,599 INFO L138 BoogieDeclarations]: Found implementation of procedure abs_int [2019-10-03 12:34:48,599 INFO L138 BoogieDeclarations]: Found implementation of procedure firstFunction [2019-10-03 12:34:48,599 INFO L138 BoogieDeclarations]: Found implementation of procedure main [2019-10-03 12:34:48,599 INFO L130 BoogieDeclarations]: Found specification of procedure __VERIFIER_error [2019-10-03 12:34:48,600 INFO L130 BoogieDeclarations]: Found specification of procedure __VERIFIER_assert [2019-10-03 12:34:48,600 INFO L130 BoogieDeclarations]: Found specification of procedure abs_int [2019-10-03 12:34:48,600 INFO L130 BoogieDeclarations]: Found specification of procedure firstFunction [2019-10-03 12:34:48,600 INFO L130 BoogieDeclarations]: Found specification of procedure main [2019-10-03 12:34:48,600 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.init [2019-10-03 12:34:48,600 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.start [2019-10-03 12:34:48,753 INFO L278 CfgBuilder]: Using the 1 location(s) as analysis (start of procedure ULTIMATE.start) [2019-10-03 12:34:48,754 INFO L283 CfgBuilder]: Removed 0 assume(true) statements. [2019-10-03 12:34:48,755 INFO L202 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 03.10 12:34:48 BoogieIcfgContainer [2019-10-03 12:34:48,756 INFO L132 PluginConnector]: ------------------------ END RCFGBuilder---------------------------- [2019-10-03 12:34:48,756 INFO L113 PluginConnector]: ------------------------Abstract Interpretation---------------------------- [2019-10-03 12:34:48,757 INFO L271 PluginConnector]: Initializing Abstract Interpretation... [2019-10-03 12:34:48,757 INFO L275 PluginConnector]: Abstract Interpretation initialized [2019-10-03 12:34:48,758 INFO L185 PluginConnector]: Executing the observer AbstractInterpretationRcfgObserver from plugin Abstract Interpretation for "de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 03.10 12:34:48" (1/1) ... [2019-10-03 12:34:48,809 INFO L101 FixpointEngine]: Starting fixpoint engine with domain IntervalDomain (maxUnwinding=3, maxParallelStates=2) [2019-10-03 12:34:48,956 INFO L263 AbstractInterpreter]: Some error location(s) were reachable [2019-10-03 12:34:48,974 INFO L272 AbstractInterpreter]: Visited 26 different actions 26 times. Never merged. Never widened. Performed 20 root evaluator evaluations with a maximum evaluation depth of 5. Performed 20 inverse root evaluator evaluations with a maximum inverse evaluation depth of 5. Never found a fixpoint. Largest state had 5 variables. [2019-10-03 12:34:48,974 INFO L132 PluginConnector]: ------------------------ END Abstract Interpretation---------------------------- [2019-10-03 12:34:48,978 INFO L168 Benchmark]: Toolchain (without parser) took 843.11 ms. Allocated memory was 140.0 MB in the beginning and 199.8 MB in the end (delta: 59.8 MB). Free memory was 87.6 MB in the beginning and 158.7 MB in the end (delta: -71.2 MB). There was no memory consumed. Max. memory is 7.1 GB. [2019-10-03 12:34:48,979 INFO L168 Benchmark]: CDTParser took 0.23 ms. Allocated memory is still 140.0 MB. Free memory was 106.1 MB in the beginning and 105.9 MB in the end (delta: 212.8 kB). Peak memory consumption was 212.8 kB. Max. memory is 7.1 GB. [2019-10-03 12:34:48,980 INFO L168 Benchmark]: CACSL2BoogieTranslator took 285.51 ms. Allocated memory is still 140.0 MB. Free memory was 87.2 MB in the beginning and 78.1 MB in the end (delta: 9.1 MB). Peak memory consumption was 9.1 MB. Max. memory is 7.1 GB. [2019-10-03 12:34:48,981 INFO L168 Benchmark]: Boogie Preprocessor took 118.63 ms. Allocated memory was 140.0 MB in the beginning and 199.8 MB in the end (delta: 59.8 MB). Free memory was 78.1 MB in the beginning and 177.8 MB in the end (delta: -99.7 MB). Peak memory consumption was 11.1 MB. Max. memory is 7.1 GB. [2019-10-03 12:34:48,982 INFO L168 Benchmark]: RCFGBuilder took 214.75 ms. Allocated memory is still 199.8 MB. Free memory was 177.8 MB in the beginning and 165.9 MB in the end (delta: 11.9 MB). Peak memory consumption was 11.9 MB. Max. memory is 7.1 GB. [2019-10-03 12:34:48,983 INFO L168 Benchmark]: Abstract Interpretation took 217.94 ms. Allocated memory is still 199.8 MB. Free memory was 165.9 MB in the beginning and 158.7 MB in the end (delta: 7.2 MB). Peak memory consumption was 7.2 MB. Max. memory is 7.1 GB. [2019-10-03 12:34:48,988 INFO L335 ainManager$Toolchain]: ####################### End [Toolchain 1] ####################### --- Results --- * Results from de.uni_freiburg.informatik.ultimate.core: - StatisticsResult: Toolchain Benchmarks Benchmark results are: * CDTParser took 0.23 ms. Allocated memory is still 140.0 MB. Free memory was 106.1 MB in the beginning and 105.9 MB in the end (delta: 212.8 kB). Peak memory consumption was 212.8 kB. Max. memory is 7.1 GB. * CACSL2BoogieTranslator took 285.51 ms. Allocated memory is still 140.0 MB. Free memory was 87.2 MB in the beginning and 78.1 MB in the end (delta: 9.1 MB). Peak memory consumption was 9.1 MB. Max. memory is 7.1 GB. * Boogie Preprocessor took 118.63 ms. Allocated memory was 140.0 MB in the beginning and 199.8 MB in the end (delta: 59.8 MB). Free memory was 78.1 MB in the beginning and 177.8 MB in the end (delta: -99.7 MB). Peak memory consumption was 11.1 MB. Max. memory is 7.1 GB. * RCFGBuilder took 214.75 ms. Allocated memory is still 199.8 MB. Free memory was 177.8 MB in the beginning and 165.9 MB in the end (delta: 11.9 MB). Peak memory consumption was 11.9 MB. Max. memory is 7.1 GB. * Abstract Interpretation took 217.94 ms. Allocated memory is still 199.8 MB. Free memory was 165.9 MB in the beginning and 158.7 MB in the end (delta: 7.2 MB). Peak memory consumption was 7.2 MB. Max. memory is 7.1 GB. * Results from de.uni_freiburg.informatik.ultimate.plugins.analysis.abstractinterpretationv2: - UnprovableResult [Line: 10]: Unable to prove that call of __VERIFIER_error() unreachable Unable to prove that call of __VERIFIER_error() unreachable Reason: abstract domain could reach this error location. Possible FailurePath: [L26] int p = 0; [L35] CALL firstFunction() [L29] CALL, EXPR abs_int(-3) [L18] COND TRUE i < 0 [L22] return -i; [L29] RET, EXPR abs_int(-3) [L29] p = abs_int(-3) [L30] CALL __VERIFIER_assert(p >= 0) [L8] COND TRUE i == 0 [L10] __VERIFIER_error() RESULT: Ultimate could not prove your program: unable to determine feasibility of some traces Received shutdown request...