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HP UX Debugging Tools Understanding Blocks and Environments

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Understanding Blocks and Environments

A block is a program unit, such as a module, a main program, a subroutine, or a function. What constitutes a block depends on the language in which the program is written. Use the list blocks command to display the blocks in the program you are debugging.

A block denes and encloses a scope, the region of source code over which a name's declaration is active. The debugger also denes blocks called `declared (for user-declared symbols), `predefined (for data types for supported languages) and `image (for the program images).

The debugger denes two environments:

The run environment is the block containing the current point of execution.

The current environment is the block to which the debugger refers when evaluating expressions.

The current environment is identical to the run environment, except when you explicitly change it to another block (by using the environment command, for example). The source le display shows an arrow at the current point

of execution. When the current environment is set to some other block, a horizontal bar appears within the block where the current environment is set.

In addition, the block containing the current point of execution is displayed after the PC Location label above the source display. The current environment block is displayed after the Current Location label.

Each time execution of the target program stops, the debugger sets the current environment to the run environment.

The debugger starts its search for ob jects within the block that corresp onds to the current environment. If the debugger cannot nd the object in the current environment, it extends its searc h into outer encompassing blocks. The debugger bases its search of outer blocks on the scope and visibility rules described in \Applying Scope and Visibility Rules".

For multi-threaded applications (implemen ted using HP DCE threads), the debugger also includes a thread component in its concept of en vironment. See \Debugging Multi-Threaded Applications" in Chapter 8 for more information on debugging multi-threaded applications.

7-2 Identifying Program Objects

Contents

HP 9000 Series 700/800 Computers Legal Notices c Copyright 1980, 1984, 1986 Novell, Inc c Copyright 1986-1992Sun Microsystems, Inc c Copyright 1990 Motorola, Inc X Window System is a trademark of the Massachusetts Institute of Technology Printing History Preface Page Page Related Documentation For more information on HP-UXprogramming, refer to the following documents: (B3476-90016) (B3906-90002) (B3906-90001) (B2355-90044) describes the xdb debugger Page Page Page Contents Page Page Page Page Figures Tables Page Overview HP/DDE at a Glance Page Shows source le line numbers An arrow indicates the current program counter location To search for text strings in the source le, select Visit:Search You can change these buttons or create additional buttons by selecting Enter debugger commands Page HP/DDE Online Help Page Page Compiling, Loading, and Executing the Target Program Preparing the Target Program Invoking the Debugger Invoking and Loading a Target Program During Debugger Startup Invoking and Loading a Target Program From the Debugger Page Attaching the Debugger to a Running Process Page Stopping the Target Program Restarting the Target Program Interrupting a Running Program Page Examining Source Files . Select or use the command to put the source le in the debugger's search path However, you can view debuggable modules by selecting or using the Executing the Target Program ere You can modify the default behavior of these buttons by selecting . The Using the go Command The go command begins or resumes target program execution Using the step Command By default, the to invoke it Page Looking at the Call/Return Stack Page Page Using Monitors (Breakpoints, Watchpoints Traces, and Intercepts) Using Monitors Setting Breakpoints Page Page Page Page Setting Watchpoints Page Individual elements in a watchpoint (suc h as som e elements in an array) can be hidden by selecting them and selecting to redisplay them clicking Page Page 2. Select the granularity (how often the value is checked) The default, Every Stop , causes the debugger to check values only when target program execution event like a breakpoint Setting Traces Page Page Page Setting Intercepts Page Page Viewing and Manipulating Target Program Data Examining Variables and Expressions Page Using the Data Value Menu As shown in Figure 4-1 a number of commands are available from the Page To specify a limit on the number of elements the command displays, use the command. For example sets the limit at In languages that support special interpretation of pointers to characters: Instead of using language-specic syntax, you can use the -indirect option to the print command as follows: Follow all pointers encountered and show the value of the object pointed to Follow pointers no further than count levels command assigns the value of to the pointer command then executes the commands b etween the brackets as long as . All output is redirected to the le Use the describe , print, and dump commands to examine buers See the online command reference for more information on the commands Examining Registers Page Page Using Debugger Commands Abbreviating Debugger Commands Entering Multiple Debugger Commands on One Line Using Command Lists Continuing Commands on the Next Line Resolving Syntax Conflicts Resolving Case Sensitivity Editing the Command Line Using the Command History Facility Recording Command Sequences for Later Playback Invoking Shell Commands from the Debugger Redirecting Input and Output Page Creating Alias and Define Macros Page Using Reserved Identifiers and Special Macros Page Page Page Combining Debugger Commands Using Action Lists Creating Conditional Action Lists Use the if command to create conditional action lists. For example, the command You can also add a command Page Page Customizing the Debugger Using the Options Menu Using Startup Command Files Using a Personal Startup File to Customize the Debugger A personal startup le typically contains commands that: Page Page Page Emulating Other Debuggers Be aware that the macros aect the input syntax of commands but have no Compatibility with dbx denes macros that let you enter commands without prexes. For example, you can specify rather than Page Identifying Program Objects Understanding Blocks and Environments Page Applying Scope and Visibility Rules Page Using Qualified Names Page Page Image Qualified Names where `image(average) contains average , to name the procedure sum Special Block Qualified Forms See Appendix B and Appendix D for information on the v alid values for Page Page Page Debugging in Special Situations Examining Core Files Core File Debugging Debugging Shared Libraries Page Debugging Multi-ThreadedApplications Page Viewing and Manipulating Threads Notice the following in the thread list: You can use these numeric identiers for commands that require a (for example Page Environment in Multi-ThreadedApplications Notice the output indicates that the current environment is in Thread Thread-SpecificDebugger Commands The two commands that apply specically to debugging threaded applications are Page Assembly Level Debugging Page Page machine address You can also use the describe command with the `va function. For example: Saving Assembly Code in a File You can determine address values from the Assembly Display window Debugging Optimized Code Optimized Code and Unoptimized Code In eect, optimization transforms a program into a dierent program The following sections describe these problems in detail Page Page Page Debugging Parent and Child Processes Debugging Applications That Use ioctl or curses Running the Debugger Remotely Line-ModeUser Interface Invoking the Line-ModeUser Interface The User Interface Startup File Screen Display Conventions Examples Single step one statement using the predened alias s Use the predened alias up to walk up the stack Page Language Managers Page C Language Manager Page Integer l j U j u] (decimal) ] (hexadecimal) ] (octal) For example, 0xFu species an unsigned hexadecimal Array slices None The type of identier ; can be used to refer to anonymous types In place of an array subscript, you can give a range of elements: Lower bound to upper C++ Language Manager Page The following are also available with the HP ANSI CC compiler: Scope resolution The following operators are available with the HP ANSI CC compiler: Dynamic cast Type identication ] (decimal) Name visible from the scope Virtual address Page FORTRAN Language Manager Declaration digits (decimal) KS ](radix = 2, 8, 10, 16; KS = 1, 2, 4, 8) For example, 16#1c6 species a hexadecimal integer Real = 4,8,16) visible from the scope location Cast the resulting value of expression of elements: Given expr to upper bound, stride of Lower bound to expr2 stride of expr3 Given expr1 to upper bound, stride of expr3 HP Pascal Language Manager =, <>, <, >, <=, >=, in Boolean Set Field selection Dereference For example, 5.48E-11 is a valid real number Pointer upper bound Example: HP-UX PA-RISCAssembly Language Manager Page Mod &, |, ^, ~ (and, or, xor, not) Name from source program Register direct Indirect Solaris SPARC Assembly Language Manager Page 8 bits as a char bits Page Target Managers by creating a link to the target type name in the directory /opt/langtools/dde/tgt . For example to make hppa a valid target type, enter the following debugger loads the manager HP-UX PA-RISCTarget Manager Page Page One of the following arguments to the command target command : dump proc [full] Prints a list of known target processes helpLists and describes the supported target commands The startup le denes the following macros: Solaris SPARC Target Manager A program invocation of the form program path [program arguments ] A UNIX signal number (integer) or one of the following UNIX signal names: Dumps registers Dumps single-precision oating-point registers Page Page Object Managers Page HP SOM Object Manager Solaris SPARC Object Manager User Interface Managers Page Graphical User Interface Manager Line-ModeUser Interface Manager SoftBench User Interface Manager Page Glossary . A block qualied name explicitly iden ties the enclosing the object and the object's name; the format is Page Page Outer debugger used to contain denitions of user-declared symbol names. You may explicitly refer to symbol names created using the command by using a A shared library that is loaded by a call within your program to shl load (3X) (on HP-UXsystems) or dlopen(3X) (on Solaris systems) and block enclosing the object and the object's name; the format is A loaded executable le or shared library . An image qualied name explicitly identies the image, module, and A shared library that is linked against your program A text area that can accept t yped keystrokes maps a statement to the instruction at which some data value may change. The The window that contains the main , the \( ): , the , the \Debugger Input: A software \trigger," such as a breakpoint, that interrupts A specication of the replacement of a previous path argument to the property sdir command by a new path argument. The new path argument replaces the old one as a directory prex in the source le directory search path . See The region of source code over which a name's declaration is active Page The program that is currently being debugged Page Page Index