Data processing: software development – installation – and managem – Software program development tool – Translation of code
Reexamination Certificate
1998-07-30
2001-08-28
Dam, Tuan Q. (Department: 2762)
Data processing: software development, installation, and managem
Software program development tool
Translation of code
C714S035000, C714S038110, C714S045000, C714S046000, C709S224000, C709S241000, C709S241000, C702S183000, C702S187000
Reexamination Certificate
active
06282701
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to software tools for assisting software developers in the task of monitoring and analyzing the execution of computer programs, such as during the debugging process.
2. Description of the Related Art
Despite the significant diversity in software tracing and debugging programs (“debuggers”), virtually all debuggers share a common operational model: the developer notices the presence of a bug during normal execution, and then uses the debugger to examine the program's behavior. The second part of this process is usually accomplished by setting a breakpoint near a possibly flawed section of code, and upon reaching the breakpoint, single-stepping forward through the section of code to evaluate the cause of the problem.
Two significant problems arise in using this model. First, the developer needs to know in advance where the problem resides in order to set an appropriate breakpoint location. Setting such a breakpoint can be difficult when working with an event-driven system (such as the Microsoft Windows® operating system), because the developer does not always know which of the event handlers (callbacks) will be called.
The second problem is that some bugs give rise to actual errors only during specific execution conditions, and these conditions cannot always be reproduced during the debugging process. For example, a program error that occurs during normal execution may not occur during execution under the debugger, since the debugger affects the execution of the program. This situation is analogous to the famous “Heizenberg effect” in physics: the tool that is used to analyze the phenomena actually changes its characteristics. The Heizenberg effect is especially apparent during the debugging of time-dependent applications, since these applications rely on specific timing and synchronization conditions that are significantly altered when the program is executed step-by-step with the debugger.
An example of this second type of problem is commonly encountered when software developers attempt to diagnose problems that have been identified by customers and other end users. Quite often, software problems appear for the first time at a customer's site. When trying to debug these problems at the development site (typically in response to a bug report), the developer often discovers that the problem cannot be reproduced. The reasons for this inability to reproduce the bug may range from an inaccurate description given by the customer, to a difference in environments such as files, memory size, system library versions, and configuration information. Distributed, client/server, and parallel systems, especially multi-threaded and multi-process systems, are notorious for having non-reproducible problems because these systems depend heavily on timing and synchronization sequences that cannot easily be duplicated.
When a bug cannot be reproduced at the development site, the developer normally cannot use a debugger, and generally must resort to the tedious, and often unsuccessful, task of manually analyzing the source code. Alternatively, a member of the software development group can be sent to the customer site to debug the program on the computer system on which the bug was detected. Unfortunately, sending a developer to a customer's site is often prohibitively time consuming and expensive, and the process of setting up a debugging environment (source code files, compiler, debugger, etc.) at the customer site can be burdensome to the customer.
Some software developers attempt to resolve the problem of monitoring the execution of an application by imbedding tracing code in the source code of the application. The imbedded tracing code is designed to provide information regarding the execution of the application. Often, this imbedded code is no more than code to print messages which are conditioned by some flag that can be enabled in response to a user request. Unfortunately, the imbedded code solution depends on inserting the tracing code into the source prior to compiling and linking the shipped version of the application. To be effective, the imbedded code must be placed logically near a bug in the source code so that the trace data will provide the necessary information. Trying to anticipate where a bug will occur is, in general, a futile task. Often there is no imbedded code where it is needed, and once the application has been shipped it is too late to add the desired code.
Another drawback of current monitoring systems is the inability to correctly handle parallel execution, such as in a multiprocessor system. The monitoring systems mentioned above are designed for serial execution (single processor) architectures. Using serial techniques for parallel systems may cause several problems. First, the sampling activity done in the various parallel entities (threads or processes) may interfere with each other (e.g., the trace data produced by one entity may be over written by another entity). Second, the systems used to analyze the trace data cannot assume that the trace is sequential. For example, the function call graph in a serial environment is a simple tree. In a parallel processing environment, the function call graph is no longer a simple tree, but a collection of trees. There is a time-based relationship between each tree in the collection. Displaying the trace data as a separate calling tree for each entity is not appropriate, as this does not reveal when, during the execution, contexts switches were done between the various parallel entities. The location of the context switches in the execution sequence can be very important for debugging problems related to parallel processing.
SUMMARY OF THE INVENTION
The present invention overcomes these and other problems associated with debugging and tracing the execution of computer programs. One aspect of the present invention is a software system that facilitates the process of identifying and isolating bugs within a client program by allowing a developer to trace the execution paths of the client. The tracing can be performed without requiring modifications to the executable or source code files of the client program. Preferably, the trace data collected during the tracing operation is collected according to instructions in a trace control dataset, which is preferably stored in a Trace Control Information (TCI) file. Typically, the developer generates the TCI file by using a trace options editor program having a graphical user interface. The options editor displays the client's source code representation on a display screen together with controls that allow the software developer to interactively specify the source code and data elements to be traced. The options editor may use information created by a compiler or linker, such as debug information, in order to provide more information about the client and thereby make the process of selecting trace options easier. Once the trace options are selected, the client is run on a computer, and a tracing library is used to attach to the memory image of the client (the client process). The tracing library is configured to monitor execution of the client, and to collect trace data, based on selections in the trace options. The trace data collected by the tracing library is written to an encoded buffer in memory. The data in the buffer may optionally be saved to a trace log file for later use.
The developer then uses a trace analyzer program, also having a graphical user interface, to decode the trace information into a human-readable form, again using the debug information, and displays translated trace information on the display screen to allow the developer to analyze the execution of the client program. In a preferred embodiment, the trace options editor and the trace analyzer are combined into a single program called the analyzer. The analyzer is preferably configured to run under the control of a multi-process operating system and to allow the developer to trace multiple threads and multiple
Barboy Dmitry
Prouss Georgi
Vorobey Anatoly
Wygodny Shlomo
Dam Tuan Q.
Knobbe Martens & Olson Bear LLP.
Mutek Solutions, Ltd.
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