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HP gnu source-level debugger 5992-4701 manual var-assign command, var-update command

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The -var-assign command

Synopsis

-var-assignname expression

Assigns the value of expression to the variable object specified by name. The object must be 'editable'.

The -var-update command

Synopsis

-var-update {name "*"}

Update the value of the variable object name by evaluating its expression after fetching all the new values from memory or registers. A '*' causes all existing variable objects to be updated.

21.14 GDB/MI variable objects 359

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HP gnu source-level debugger 5992-4701 manual var-assign command, var-update command

Contents

Debugging with GDB Manual Page Table of Contents Stack frames Continuing and stepping SignalsPrint settings Value history BreakpointsExamining the Symbol Table Specifying a Debugging Target Commands for heap profiling Stop when freeing unallocated or deallocated blocksScramble previous memory contents at malloc/free calls Batch ModeExample Illustrating Execution Path Recovery Support for the info target CommandSupport for the dumpcore command Enhancements to the dumpcore commandDetecting memory leaks using GDB under Aries Command for evaluating the address of an expressionSupport for steplast command for C and C++ Debugging the application using GDB under AriesHP-UX Terminal User Interface Command files 289 Commands for controlled output 290 Miscellaneous commands 265 16.3Setting Command History Feature in GDB 281 17.4 User-defined commands 287 18.2304 20.7 Errors 302 20.822.2 How to report bugs 361 20.9 Invalidation notices 303List of Tables List of Examples Contributors to GDB Summary of GDBFree Software Page Contributors to GDB Page Loading the Executable Let us use GDB to try to see what is going onSample GDB Session Running the executable under GDB Setting Display widthSetting Breakpoints Here we describe how to set a breakpointPrinting Variable Values Stepping into a subroutineExamining the Stack Listing Source Code Setting Variable Values During a SessionGdb c Continuing Definebaz,defnQUOTEfooUNQUOTE Baz Page Invoking GDB Getting In and Out of GDBFiles Choosing filesChoosing modes Processed. See Command filesLike two `\032 characters, followed by the file name GNU Emacs sets this option when it runs GDB as aLine number in a standard, recognizable fashion each Time a stack frame is displayed which includes eachEmacs Interface Quitting GDBRedirecting WDB input and output to a file Shell commands Page Command completion GDB CommandsCommand syntax GDB sounds bell press TAB again, to see Help , h Short list of named classes of commandsGetting help This is intended for use by GNU Emacs Apropos reloadResults CompleteGetting help Page Arguments, so that you may use normal Running Programs Under GDBCompiling for debugging Starting your programDirectory See Arguments To Your ProgramYour program. SeeProgram Environment Program. See Program Input and Output Arguments To Your ProgramProgram Environment Do not supply varname, print the names For example, this commandDisplay the list of search paths for executables Path environment variableProgram Input and Output Working directoryDebugging a Running Process Killing the child process Debugging programs with multiple threads New process 35 thread Display a summary of all threads currently Here are commands to get more information about threadsThread apply command allows you to With the command argument threadnoDebugging programs with multiple processes Fork. The child process runs New process. The mode can beUnimpeded. This is the default Set the debugger response to a program callBreakpoints Stopping and ContinuingSetting breakpoints Breakpoints See Break conditions page 59, for moreBreakpoint is BreakpointCatchpoint WhetherBreakpoints are When hitEnabled Marked to beSetting catchpoints Shared library, or the unloading Call to vfork. This is currently onlyIs currently only available for HP-UX Unloading of any dynamically loadedSelecting a frame page 73 . When Deleting breakpointsDisabling breakpoints Break conditions Use condition, GDB checks expression Breakpoint, GDB prints an error messageNo symbol foo in current context Stops your program only if the valueBreakpoint command lists Breakpoint menus Cannot insert breakpoints Conditions Continuing and steppingFunction Setting breakpoints page 52. This form of the command Stops. See Automatic display SignalsInfo handle is an alias for info signals Stopping and starting multi-thread programs Stopping and Continuing Stack frames Examining the StackBacktraces Commands for Examining the StackStacks Without frames Selecting a frame Information about a frame Have existed longer. n defaults to oneWhen used without any argument, this command does not With an argument, this command is used to select a stackSetting catchpoints Page Show listsize Examining Source FilesPrinting source lines ListSearching source files Specifying source directories Contains Source and machine codeShow directories Disassembling the program via Set disassembly-flavorDisassemble or x/i commands Select the instruction set to use whenPage To See Artificial arrays page 85, for more information Following forms of print command are supportedExamining Data ExpressionsNormally supposed to reside at addr Where it is defined. See Program variablesProgram variables Type addrArtificial arrays You can print the contents of array withOutput formats Time you use either x or print Machine instruction. The default isExamining memory Print, s null-terminated string, orHowever, the count n must come first wx4 does not work For fmt i or s, or including a unit-size or a number Automatic displayFor fmt specifying only a display format and not a size or See Output formatsPrint settings Address A symbol. This is the defaultFile name and line number of a symbol Symbolic form of an addressShort strings. The default is off Default is offStrings. When GDB starts, this limit is set to Setting number-of-elementsto zeroDefault This is the default formatShow which format GDB is using to print Print using only seven-bit characters if thisWould print These settings are of interest when debugging C++ programsDefault is on Show whether C++ names in assembly listingsValue history Convenience variables Program being debugged terminates Command, in which case it is a pointer to the type of $Format in which the data was printed $exitcodeOr add four to the stack pointer3 with3with RegistersInfo registers Info all-registers Info registers regname Or print the instruction to be executed next withThis is what the macro produces Printing Floating Point ValuesFloating point hardware To get the bit pattern, try the following macro100 Cpp Using GDB with Different LanguagesSwitching between source languages List of filename extensions and languagesFiles Setting the working languageNot skip over function prologues when stepping Having GDB infer the source languageAn overview of type checking Displaying the languageType and range checking An overview of range checking Supported languages C++ Types and pointer types Expressions is 0 for false and non-zero for trueNon-zero for true Left shift, and right shift. Defined on integral typesC++ constants Class typesDouble colons also represent the GDB scope operator see Expressions page 83. Same precedence as , aboveGDB expression handling can interpret most C++ expressions 1.3 C++ expressionsC++ type and range checks C++ defaultsPrinting the variable or class returns See Breakpoint menus GDB features for C++GDB and C Breakpoint menusFortran types supported FortranFortran types Greater than or equal to Less thanLess than or equal to Greater thanBlock Fortran special issuesCommonblockname Examining the Symbol Table For example, for this variable declaration Two commands give this outputAs with whatis, using ptype without an Symbols will be read when neededOnce. This is the default Allow GDB to reload the symbols forReplace symbol definitions Do not replace symbolClass, or union―for example, struct SettingIs in another source file. The default is on Tell GDB to resolve opaque types. An opaqueAssignment to variables Altering ExecutionStores the value 4 into that memory location Continuing at a different addressReturning from a function Giving your program a signalYou can use the following command to return from a function Is used as the return value from the function value Calling program functionsPatching programs Return , returnPatching programs 124 GDB Files Commands to specify filesSee Optional warnings and messages Map in symbol information from this auxiliary Option with any of the commands that loadGDB has the entire symbol table available Write the symbols for your program into aSection New library has been loaded, until the symbol Symbols were loaded. Both the commands listTo display or set the threshold, use the commands If threshold is nonzero, symbols from allMegabytes Names where the desired shared libraries reside. GDBSearching the default system directories Specifying shared library locationsMessages Errors reading symbol filesVerbose on. See Optional warnings Debug your program, though certain symbols Symbol scope block as starting on the previousIs the symbol type of the uncomprehended GDB circumvents the error by ignoring thisActive targets Commands for managing targetsSpecifying a Debugging Target See Commands to specify files Choosing target byte order Display GDBs current idea of the target byte order Instruct GDB to assume the target is big-endianInstruct GDB to assume the target is little-endian ExecutableSummary of HP Enhancements to GDB HP-UX Configuration-Specific InformationSupport for setting breakpoints using shared library name Implementation of ask mode for set follow-fork-modeCommand watchtarget Dependent Standard Library Routines for Run Time Checking HP-UX dependenciesLinker Dependencies Getpid Close Srand Strchr Abort Unlink AtoiSupported Platforms and Modes GDB location HP-UX targetsSupport for Alternate root WDB LocationBin $WDBROOT/bin Specifying object file directoriesLibrtc.sl location $WDBROOT/bin Opt/langtools/ n/a NoneFix and continue debugging Fix and Continue restrictions Fix and Continue compiler dependenciesUsing Fix and Continue Run the program Example Fix and Continue sessionCompile the program Make the necessary changes. In this case, add return total Gdb b mainGdb run Gdb editGdb q Inline SupportInline Debugging in HP 9000 Systems Step next list backtrace frame n info locals info args Breakpoint info frame disassemblyFollowing options available for the set inline-debugcommand Inline Debugging in Integrity SystemsDebugging Inline Functions in Integrity Systems LimitationsViewing and Evaluating Macro Definitions Info frame disassemblyDebugging Macros Debug=none Compiler Options to Enable Macro DebuggingEvaluating Macros Examples for Macro Debugging HP-UX Configuration-Specific Information Debugging Memory Problems Memory Debugging Methodologies When to suspect a memory leakMemory debugging restrictions Debugging Memory in Interactive Mode Command discards the data existing in the file Displays all current settings for memoryThis command are ignored from report. If Heap growth. The default value is 100. EveryDebugging Memory Problems Such as attempting to access space that is freed Debugging when the string option is set forHave occurred and WDB reports the problem Specific pattern when it is allocated orUser-specified value Use the info command to show list of memory leaksIf the user specifies a value less than 16 for Number of bytes, the debugger ignores itGdb info leak Debugging Memory in Batch ModeSetting Configuration Options for Batch Mode Sets the number of frames to be printed for leak context Framecount=noframes or set heap-check frame-count noframesFor 64-bit IPF applications For 32 bit IPF applicationsFor 64 bit IPF applications For 64 bit PA applicationsLdpreload Environment variable setting for Batch mode debuggingStderr error message goes to stderr Aborts execution when heap objectsAborts execution when out of memory Log file for batch mode must beExample for Batch Mode RTC Complete one of the following steps Run the program as follows Rtcconfig file should contain entries such as the followingPreload the librtc library as follows For 32 bit PA applications Specifying minimum leak size Configuring memory debugging settingsRun the program Start a debugging session as follows Specifying the stack depthSpecifying minimum block size Stop when freeing unallocated or deallocated blocksScenarios in memory debugging For example, if you useDetect dangling pointers and dangling blocks Scramble previous memory contents at malloc/free callsInteractive debugging mode set heap-check scramble on off SyntaxDetect in-block corruption of freed blocks Off Memory Debugging Commands in Interactive and Batch ModeAs the start of the heap, end of the heap, heap Commands for heap profilingPoint you use the info heap command Heap ProfilingSet a breakpoint This example shows how to use this feature on HP-UXChanges for a given run Commands to track the change in data segment valueSupport for Enabling and Disabling Specific Threads Thread Debugging SupportAdvanced Thread Debugging Support Backtrace Support for Thread DebuggingPre-requisites for Advanced Thread Debugging Enabling and Disabling Advanced Thread Debugging FeaturesCv-multiple-mxs onoff The set thread-check cv-multiple-mxs Onoff command checks if an applicationUnlock-not-own onoff The set thread-check unlock-not-own Mixed-sched-policy onoff The set thread-checkDifferent mutexes. The debugger transfers This returns an Einval error toUser and prints a warning message when this Command checks if any thread has terminatedCreated with the detach attribute. When an When this condition is detected. This situationCommand checks if a thread has terminated Exception or a cancel without joining orRwlock-id is provided, the command displays Provided, the command displays extendedIs provided, the command displays extended Condvar-id is provided, the command displaysFor 64-bit PA applications Thread Debugging in Batch Mode For 64-bit PA applications, set Pre-requisites for Batch mode of Thread DebuggingFor 64 bit IPF applications, set Set the environment variable Batchrtc to on as And/OrOpt/langtools/lib/hpux64/librtc.so Limitations in Batch mode of thread debugging Thread Debugging in +check ModeWhere Pid is the process id Debugging MPI Programs Where pid is the process identifierIssue Debugger response to a program call to fork or vfork is ask Ask mode for set follow-fork-modeSerial mode for set follow-fork-mode Support for showing unwind infoPrinting CFM and PFS registers Command to Search for a Pattern in the Memory Address SpaceWithin double quotes. This parameter is mandatory Parameter is mandatory when end-addressis notSpecifies the length of the memory address range. This String value. The character pattern must be enclosedExample 14-1 Sample Output for the find command Specifies the pattern expr1 Using the /max-countparameterUsing the /size-charparameter Str0 Specifies the starting addressGenerating core files with packcore /unpackcore/getcore Debugging Core FilesSupport for the info target Command Enhancements to the dumpcore command Support for the dumpcore commandWhen starting from the HP WDB command line When starting from the shell promptSample Output When starting from shell promptSupport for display of run time type information Info rtti addressExec-path updownpathindex aliased to ep Info exec-path summaryInfo global-exec-path summary Sample Debugging Session Example Illustrating Execution Path RecoverySample Program Command to Unwind Beyond 10000 Frames Invoking GDB Before a Program Aborts Aborting a Command Line CallHardware watchpoints Instruction Level SteppingEnhanced support for watchpoints and breakpoints Deferred watchpointsRdp Support for procedural breakpointsSupport for template breakpoints RbpDebugging support for shared libraries Using shared library as main programPrivately mapping shared libraries Setting Deferred Breakpoints in Shared LibraryUsing catch load Opt/langtools/bin/pxdb -s on executable-name Selectively Mapping Shared Libraries As PrivatePrinting Decimal Floating point data types Setting breakpoints in shared libraryEnhancement to the info shared Command Debugging support for Decimal Floating Point data typeEvaluating Decimal Floating Point data types Following are sample commands to print NaT registersPrinting NaT Registers Handling Decimal Floating Point Data typesPrinting type of Decimal Floating Point variable Assignment of Decimal floating point value to variableArithmetic Operations Comparison OperationsThis prints the binary floating point value as double Additional Support for binary floating point data typeSupport for Binary Floating Point constants f, l This prints the binary floating point value as oatEnhanced Java Debugging Support Java Stack Unwind FeaturesLanguage support Gdb help java Gdb Subcommands for Java VM DebuggingStack frame Frame command of GDB has been enhanced to interpret a JavaJava and native stack frames Info frameJava corefile debugging support Java attach mode debugging supportSyntax Enhanced support for C++ templatesSupport for debugging namespaces Support for fpreg data type on IPFSupport for Complex variables in HP C This is equivalent to executing Command for evaluating the address of an expressionViewing Wide Character Strings Support for dumping array in an Ascii file Support for output loggingSupport for debugging typedefs Support for steplast command for C and C++Support for Fortran array slices Displaying enumeratorsGetting information from a non-debug executable Break Call Cond Jump Return Print Set var Watch Whatis Debugging optimized codeBreak Call Clear Disassem List HP-UX Configuration-Specific Information 14.29.1.2 +O2/+O3/+O4/-ipo Debugging Optimized Code at Various Optimization Levels14.29.1.1 +O0 and +O1 +O2 or -O Following limitations apply when debugging optimized codeDebugging with Aries Limitations of GDB Support under Aries Debugging the application using GDB under AriesAttaching GDB to an already running emulated process Detecting memory leaks using GDB under AriesStarting and stopping Visual Interface for WDB Visual Interface for WDBVisual Interface for WDB GUI display Navigating the Visual Interface for WDB displaySpecifying foreground and background colors Using the X-window graphical interfaceFor dterm, use the following Using the TUI modeChanging the size of the source or debugger pane Loading source files Using commands to browse through source filesEditing the command line and command-line history Saving the contents of a debugging session to a fileStop in/at dbx commands Support for XDB commandsGNU GDB Logging Commands Support for command line calls in a stripped executableFor 32-bit applications Execute the chatr -B immediate executable commandPrinting of locals and globals in a stripped module Command line calls to non-stripped librarySupport for debugging stripped binaries For 64-bit applicationsSyntax Displaying the current block scope informationLinux support 242 Main Invoke the debugger using a command like the followingHP-UX Terminal User Interface Starting the TUIScreen Layouts Automatically running a program at startupPane looks like this Disassembly paneDisassembly pane appears when you issue the command Source paneSource/Disassembly pane appears when you issue the command Source/Disassembly paneDisassembly/Register pane Source/Register pane Source/Register pane appears when you issue the commandChanging pane focus Use the commandsToggle split-screen mode Cycling through the panesFs regs Foc next Changing the register display Scrolling panesChanging the pane size Refreshing and updating the window XDB to WDB Transition Guide By-function lists of XDB commands and HP WDB equivalentsWindow mode commands Invocation commandsWindow mode commands Invocation commandsFile viewing commands File viewing commandsData Viewing and modification commands Source directory mapping commandsLl string Lm string Data viewing and modification commandsStack viewing commands Stack viewing commandsJob control commands Status-viewing commandJob control commands Status viewing commandsOverall breakpoint commands Overall breakpoint commandsAuxiliary breakpoint commands 10 Breakpoint creation commands Breakpoint creation commandsAuxillary breakpoint commands 11 Overall breakpoint commands Breakpoint status commandsBp bpt bpx dp Dpt Dpx All-procedures breakpoint commandsGlobal breakpoint commands 12 Global breakpoint commandsMacro facility commands Assertion control commandsRecord and playback commands 14 Signal control commands Signal control commandsMiscellaneous commands 13 Macro facility commandsXDB data formats and HP WDB equivalents Format of the print command is different in XDB and GDB16 Data format commands Decimal integer XDB special language operators and HP WDB equivalents 17 Macro facility commandsXDB location syntax and HP WDB equivalents 19 Special variables XDB special variables and HP WDB equivalents18 Special language operators 20 Variable Identifiers Alphabetical lists of XDB commands and HP WDB equivalentsXDB variable identifiers and HP WDB equivalents 16.8.1 a22 B 16.8.2 B23 C through D Through D25 L Through K16.8.5 L 24 F through K26 M through P Through P28 T Through S16.8.8 T 27 Q through S29 U through Z Through Z30 Symbols SymbolsAny string Control-C # text 280 Controlling GDB Setting the GDB PromptSetting Command Editing Options in GDB Setting Command History Feature in GDBExpansion or through the history command Control the settingsTo fname. This is the file where GDB reads an Exits. You can access this list through historySupported Number Formats Setting the GDB Screen SizeOptional warnings and messages Show confirm Displays state of confirmation requests Optional messages about internal happeningsSet confirm on Object debugging info Show debug varobjUser-defined commands Canned Sequences of CommandsUser-defined command hooks To add source directories or Command filesCommands for controlled output Output formats Expressions292 Using GDB under gnu Emacs GDB up command Calls, like the GDB next command. Then update the displayExecute to next instruction, using the GDB nexti command Update display window accordingly295 296 Server prefix What is an annotation?GDB Annotations Values When printing a structure, GDB annotates it as followsFrame annotation begins with When printing an array, GDB annotates it as followsFrames Then comes Annotation for GDB input DisplaysInformation on breakpoints ErrorsRunning the program Invalidation noticesDisplaying source Target-invalid Annotations We Might Want in the Future306 GDB/MI Interface 21.1 GDB/MI Command SyntaxPragmatics Done running connected error exit21.1.2 GDB/MI Output syntax Value Const tuple list String Tuple → Here is an example to evaluate an expression Here is what happens if you pass a bad command21.2 GDB/MI compatibility with CLI Simple examples of GDB/MI interaction21.3.2 GDB/MI stream records 21.4 GDB/MI command description format21.3 GDB/MI output records 21.3.1 GDB/MI result records-break-after Command 21.5 GDB/MI breakpoint table commandsCorresponding GDB command is condition -break-condition commandCorresponding GDB command is disable -break-delete command-break-disable command Corresponding GDB command is delete-break-info Command -break-enable commandResult -break-insert command-break-list command Setting a watchpoint on a variable in the main function -break-watch commandCorresponding GDB commands are watch, awatch, and rwatch Exec-continue running gdb 21.6 GDB/MI Data manipulation -data-disassemble commandDisassemble 3 instructions from the start of main There is no direct mapping from this command to the CLIDisassemble from the current value of $pc to $pc + -data-evaluate-expression command On a PPC MBX board -data-list-changed-registers Command-data-list-register-names command Display a list of the registers that have changed-data-list-register-values command To be read. Complex expressions containing embedded white -data-read-memory commandSpace should be quoted using the C convention Word-format Word-sizenr-rowsnr-cols aschar -display-disable Command -display-delete command-environment-cd command -display-enable command-display-insert Command -display-list command-environment-path command -environment-directory commandShow the current working directory -environment-pwd commandCorresponding GDB command is pwd 21.7 GDB/MI program control-exec-continue command -exec-abort command-exec-arguments command Corresponding GDB command is interrupt -exec-finish command-exec-interrupt command Corresponding GDB command is finishCorresponding GDB command is nexti -exec-nextcommand Synopsis-exec-next-instruction command Corresponding GDB command is nextCorresponding GDB command is run -exec-return command-exec-runcommand Synopsis Corresponding GDB command is returnExample -exec-stepCommand Synopsis -exec-show-arguments commandRegular stepping -exec-step-instruction command-exec-until command Corresponding GDB command is stepiCorresponding GDB command is file -file-exec-and-symbols command-file-exec-file command Corresponding GDB command is until-file-list-shared-libraries command -file-list-exec-sections command-file-list-exec-source-files command -gdb-exitcommand Synopsis Miscellaneous GDB commands in GDB/MI-file-list-symbol-files command -file-symbol-file command-gdb-version command -gdb-setcommand Synopsis-gdb-showcommand Synopsis -stack-info-depth command 21.9 GDB/MI Stack Manipulation Commands-stack-info-frame command For a stack with frame levels 0 through -stack-list-arguments command Synopsis-stack-list-frames command Show a single frame Corresponding GDB commands are backtrace and whereFull stack backtrace Show frames between lowframe and highframeInfo locals in GDB, gdbgetlocals in gdbtk -stack-list-locals command-stack-select-frame command -symbol-info-function command 21.10 GDB/MI Symbol query commands-symbol-info-address command -symbol-info-file command-symbol-list-types command -symbol-info-line command-symbol-info-symbol command -symbol-list-functions command-symbol-type command -symbol-list-variables command-symbol-locate command -target-detach command 21.11 GDB/MI Target Manipulation Commands-target-attach command -target-compare-sections commandAt the end, a summary is printed -target-download commandCorresponding GDB command is load Name of the section-target-exec-status command -target-list-parameters command -target-list-available-targets command-target-list-current-targets command -thread-list-all-threads command 21.12 GDB/MI thread commands-target-select command -thread-info command-thread-select command -thread-list-ids command21.14 GDB/MI variable objects 21.13 GDB/MI tracepoint commandsTracepoint commands are not yet implemented Description and use of operations on variable objects -var-create commandGDB/MI Operations -var-info-num-children command -var-delete command-var-set-format command -var-show-format command-var-show-attributes command -var-list-children command-var-info-type command -var-info-expression command-var-update command -var-assign command360 Have you found a bug? How to report bugsReporting Bugs in GDB Reporting Bugs in GDB How to report bugs 364 Installing GDB Package Compiling GDB in another directoryGdb-gdb-199991101/mmalloc Specifying names for hosts and targets Srcdir= dirname Configure optionsSeparate directories. configure writes configuration To use the source in the directory dirname. configureAll available targets Target=target