Tracing stack and heap overflow errors - Mbed

To monitor and debug memory overflow issues, mbed OS 5 provides runtime statistics for stack and heap usage. To make it easier to dynamically ... 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ClassicCompilerforMbedprojects. LoginorSignup LoginorSignup Overview Operatingsystem MbedOS Developmenttools MbedStudio KeilStudio MbedCLI Securityandconnectivity MbedTLSandMbedCrypto Connectivity Ecosystem Ourpartners Hardware Boards Modules Components Hardwareoverview&MbedEnabled MbedHDK Code Documentation MbedOS MbedStudio KeilStudio Casestudies Community Forum Contribute MbedOSTechForum Reportaproblem Blog UpcomingmaintenanceonMbedsites:Tuesdays1000-1100UTC|Learnhowthismightaffectyou Blog »Tracingstackandheapoverflowerrors Tracingstackandheapoverflowerrors Lastupdated14Aug2018,byJanJongboom. mbedOS5, memory, outofmemory, RTX WarningThisarticleisoutdated.Forthelatestversionofthisarticle,seeTrackingmemoryusagewithMbedOS. Ifyouhaveeverseenthelightsofdeadonyourdevelopmentboard,accompaniedbyanRTXerrorcode:0x00000001orOperatornewoutofmemorymessageontheserialport,youhavehitamemoryoverflowbug.Memorymanagementremainsadifficultproblemonmicrocontrollers.Notonlyismemorylimited,butalsomicrocontrollersdonothaveanMMUandthereforecannotmovememoryblocksaroundwithoutchangingaddresses.Thislackofvirtualmemorymeansyouhavetohavefixedstacksizes,soyoucanrunintoastackoverflowerrorevenwhenthereisstillRAMavailable. Tomonitoranddebugmemoryoverflowissues,mbedOS5providesruntimestatisticsforstackandheapusage.Tomakeiteasiertodynamicallyusetheseruntimestatistics,MaxVilimpoc-embeddedsoftwareleadatunuGmbHinGermany-releasedthembed-memory-statuslibrary,whichthisblogpostusestoanalyseanddebugbothastackoverflowandaheapallocationerror. Inaddition,thispostshowshowyouuseMax'slibrarytotrackusageoftheISRstack,whichthembedOS5runtimestatisticsdonotprovide. Addingmbed-memory-statustoyourproject Ifyou'reusingtheonlinecompiler: Right-clickonyourproject. ChooseImportLibrary>FromURL. Under'SourceURL',enter:https://github.com/nuket/mbed-memory-status ClickImport. Ifyou'reusingmbedCLI,run: $mbedaddhttps://github.com/nuket/mbed-memory-status Enablingruntimestatistics Openorcreatethembed_app.jsonfile,andfillitwith: { "macros":["DEBUG_ISR_STACK_USAGE=1","MBED_HEAP_STATS_ENABLED=1","MBED_STACK_STATS_ENABLED=1"] } Thisenablesstack,heapandISRstackstatistics. Note:Ifyou'reusingtheonlinecompiler,removetheDEBUG_ISR_STACK_USAGE=1macro. ISRstatistics TheISRstackisnotcoveredbythembedOSruntimestatisticsbutisanextensionmadebythembed-memory-statuslibrary.Trackingworkslikethis: Thelibraryregistersafunctioninthestartup(*.S)scriptfortheapplication. ThisfunctionfillstheISRstackwithplaceholdervalues(0xAFFEC7ED)butwithoutaffectingthestackpointer. WhenrequestingtheavailablespaceontheISRstack,thecodeinspectsthememoryreservedfortheISRstackandseeswhichpartofthememoryhasnotchanged. Toenablethesestatistics,you'llneedtomodifythestartupscriptforyourdevelopmentboard.Thisonlyworksifyou'recompilinglocallywithGCC,notintheonlinecompiler.Instructionsarehere. Note:Thisapproachunfortunatelydoesnottrackfreedmemory. Viewingmemoryregions Nowthatyouhaveenabledruntimestatistics,youcanviewthememoryregions.Thisisusefulbecauseitgivesyouinsightinthethreadsthatarerunning,thestacksizesofthesethreadsandtheavailableheapmemory.ThisisespeciallyusefulwhendebuggingstackoverflowerrorsbecauseitshowsthememoryregionsandthreadIDs. ToviewtherunningthreadsandtheheapandISRstacksizes,addtheselinestoyourmain()function: #include"mbed_memory_status.h" intmain(){ print_all_thread_info(); print_heap_and_isr_stack_info(); Formbed-os-example-blinkycompiledwithGCC_ARM,runningonaFRDM-K64Fthisresultsinthefollowingoutput: stack(start:20002690end:200029B0size:00000320used:00000070)thread(id:200029F8entry:00002E8D) stack(start:20000B7Cend:20001B7Csize:00001000used:00000098)thread(id:20002A38entry:000025F1) stack(start:20002DC8end:20002FC8size:00000200used:00000040)thread(id:2000301Centry:00002639) heap(start:20003130end:2002F000size:0002BED0used:00000000)alloc(ok:00000000fail:00000000) isr_stack(start:2002F000end:20030000size:00001000used:00000400) Youseethreethreadsrunning,theirmemoryregionsandtheamountofstackspaceused.Toseewhatthesethreadsare,youcaninspectthe.elffile(onadebugbuild)via: arm-none-eabi-nmmbed-os-example-blinky.elf Lookingforentrieswithoffsetentryminus1(Whyminus1?): 00002e8cTosTimerThread 000025f0Tpre_main 00002638Tos_idle_demon Debuggingastackoverflowerror Nowthatyouknowwhichthreadsarerunningandthememoryspacethattheyareusing,youcantriggerastackoverflowerror.Thefollowingprogramoverflowsthestacksizeofthemainthread(0x1000bytesontheK64F)afterasecond: #include"mbed.h" #include"mbed_memory_status.h" intmain(){ uint8_tbig_arr[1024]; for(size_tix=0;ix