U.S. patent application number 14/602654 was filed with the patent office on 2015-11-19 for debugging data format conversion.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Jeremy P. Blackman, Bret W. Dixon, Adrian N. Simcock.
Application Number | 20150331783 14/602654 |
Document ID | / |
Family ID | 54538617 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150331783 |
Kind Code |
A1 |
Blackman; Jeremy P. ; et
al. |
November 19, 2015 |
DEBUGGING DATA FORMAT CONVERSION
Abstract
In an approach for generating a compiler listing using Debugging
With Attributed Record Format (DWARF) debugging data, a processor
receives DWARF debugging data associated with source code of a
programming language. A processor extracts information from the
DWARF debugging data, wherein the information comprises at least
source code lines, variable declaration lines, and variable
reference lines. A processor generates a compiler listing based on
the information extracted from the DWARF debugging data, wherein
the compiler listing includes at least a symbol table, and
cross-reference information.
Inventors: |
Blackman; Jeremy P.;
(Mullaloo, AU) ; Dixon; Bret W.; (South Perth,
AU) ; Simcock; Adrian N.; (Perth, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
54538617 |
Appl. No.: |
14/602654 |
Filed: |
January 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14279865 |
May 16, 2014 |
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14602654 |
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Current U.S.
Class: |
717/124 |
Current CPC
Class: |
G06F 11/366 20130101;
G06F 11/362 20130101; G06F 11/3624 20130101; G06F 11/3636
20130101 |
International
Class: |
G06F 11/36 20060101
G06F011/36 |
Claims
1. A method for generating a compiler listing using Debugging With
Attributed Record Format (DWARF) debugging data, the method
comprising: receiving, by one or more processors, DWARF debugging
data associated with source code of a programming language;
accessing, by one or more processors, a debugging information entry
(DIE) of the DWARF debugging data; retrieving, by one or more
processors, a variable declaration line and a variable data name
for a variable from the DIE; identifying, by one or more
processors, a line of the source code that references the variable;
determining, by one or more processors, the line of the source code
modifies the variable; generating, by one or more processors, a
compiler listing based on the information extracted from the DWARF
debugging data, wherein the compiler listing includes at least a
symbol table, and cross-reference information; and annotating, by
one or more processors, a reference to the line of the source code
within the compiler listing, indicating that the variable is
modified at the line of the source code.
2. (canceled)
3. The method of claim 1, wherein the step of receiving DWARF
debugging data associated with source code of a programming
language comprises: receiving, by one or more processors, the
source code; compiling, by one or more processors, the source code;
and generating, by one or more processors, the DWARF debugging
data.
4. The method of claim 1, wherein the cross-reference information
comprises a listing of variables and source lines where each
variable of the listing is referenced.
5. The method of claim 1, wherein the symbol table includes
variable names, base locator information, and assembler data
definition information.
6. The method of claim 1, further comprising: consuming, by a
debugger incompatible with DWARF debugging data, at least the
compiler listing.
7. The method of claim 1, wherein the programming language is
COBOL.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
debugging software, and more particularly to generating a compiler
listing using DWARF debugging data format information.
BACKGROUND OF THE INVENTION
[0002] A debugging data format is a means of storing information
about a compiled program for use by high-level debuggers. Modern
debugging data formats may store enough information to allow
source-level debugging. The Debugging With Attribute Record Format
(DWARF) and symbol table entries (STABS) formats are the most
widely used executable and linking format (ELF). Other debugging
formats include common object file format (COFF), PE-COFF, object
module format (OMF), and IEEE-695.
[0003] DWARF is a more recent format for ELF files. DWARF was
created to overcome shortcomings in STAB, allowing for more
detailed and compact descriptions of data structures, data variable
movement, and complex language structures, such as in C. The
debugging information is stored in sections in the object file.
[0004] The basic descriptive entity in DWARF is the debugging
information entry (DIE). A DIE has a tag that specifies what the
DIE describes and a list of attributes that fills in details, and
further describes the entity. Attributes may contain a variety of
values: constants (such as a function name), variables (such as the
start address for a function), or references to another DIE (such
as for the type of a function's return value).
SUMMARY
[0005] Aspects of an embodiment of the present invention disclose a
method, computer program product, and computing system for
generating a compiler listing using Debugging With Attributed
Record Format (DWARF) debugging data. A processor receives DWARF
debugging data associated with source code of a programming
language. A processor extracts information from the DWARF debugging
data, wherein the information comprises at least source code lines,
variable declaration lines, and variable reference lines. A
processor generates a compiler listing based on the information
extracted from the DWARF debugging data, wherein the compiler
listing includes at least a symbol table, and cross-reference
information.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0006] FIG. 1 depicts a diagram of a computing system, in
accordance with one embodiment of the present invention
[0007] FIG. 2 depicts a flowchart of the steps of a debugging data
converter executing within the computing system of FIG. 1, for
converting DWARF debugging data into a compiler listing format, in
accordance with one embodiment of the present invention.
[0008] FIG. 3 depicts a block diagram of components of the server
executing a debugging data converter, in accordance with one
embodiment of the present invention.
DETAILED DESCRIPTION
[0009] Embodiments of the present invention recognize that many
modern compilers have moved to a standardized debugging data format
called DWARF. Embodiments of the present invention recognize that
not all modern debuggers support the DWARF debugging data format.
Embodiments of the present invention propose a method, computer
program product, and computer system that allows for the conversion
of DWARF debugging data into a compiler listing. A compiler listing
is a type of compiler output that contains information about a
particular compilation. As a debugging aid, a compiler listing is
useful for determining what has gone wrong in a compilation.
[0010] The present invention will now be described in detail with
reference to the Figures.
[0011] FIG. 1 depicts a diagram of computing system 10, in
accordance with one embodiment of the present invention. FIG. 1
provides only an illustration of one embodiment and does not imply
any limitations with regard to the environments in which different
embodiments may be implemented.
[0012] In the depicted embodiment, computing system 10 includes
server 20. Computing system 10 may also include a network, servers,
computing devices, or other devices not shown.
[0013] Server 20 may be a management server, a web server, or any
other electronic device or computing system capable of processing
program instructions and receiving and sending data. In some
embodiments, server 20 may be a laptop computer, tablet computer,
netbook computer, personal computer (PC), a desktop computer, a
personal digital assistant (PDA), a smart phone, or any
programmable electronic device. In other embodiments, server 20 may
represent a server computing system utilizing multiple computers as
a server system, such as in a cloud computing environment. Server
20 contains source code 110, compiler 120, debugging data
repository 130, debugging data converter 140, and debugger 150.
Server 20 may include components, as depicted and described in
further detail with respect to FIG. 3.
[0014] Source code 110 is a generic set of source code to be
compiled by compiler 120. Embodiments of source code 110 may be
written in COBOL, C++, Smalltalk, or other programming languages.
In some embodiments, source code 110 resides on server 20. In other
embodiments, source code 110 may reside on another server or
another computing device, provided that source code 110 is
accessible to compiler 120.
[0015] Compiler 120 is a compiler that generates DWARF debugging
data during the compilation of source code, such as source code
110. A compiler transforms source code written in a programming
language, i.e., the source language, into another computer
language, i.e., the target language, which is often object code. In
some embodiments, compiler 120 stores DWARF debugging data to a
repository, such as debugging data repository 130, for access by
debugging data converter 140. In some embodiments, compiler 120 is
a function of an integrated development environment (IDE). In other
embodiments, compiler 120 is a stand-alone compiler. An IDE is a
software application that provides comprehensive facilities to
computer programmers for software development, such as source code
editors, build automation tools, compilers, interpreters,
debuggers, etc. In one embodiment, compiler 120 resides on server
20. In another embodiment, compiler 120 may reside on another
server or another computing device, provided that compiler 120 has
access to source code 110 and debugging data repository 130.
[0016] Debugging data repository 130 may be a repository that may
be written and read by compiler 120, debugging data converter 140,
and debugger 150. DWARF debugging data and converted debugging data
may be stored to debugging data repository 130. In some
embodiments, converted debugging data may be annotated to indicate
corresponding DWARF debugging data. In one embodiment, debugging
data repository 130 resides on server 20. In other embodiments,
debugging data repository 130 may reside on another server or
another computing device, provided that debugging data repository
is accessible to compiler 120, debugging data converter 140, and
debugger 150.
[0017] Debugging data converter 140 operates to convert DWARF
debugging data into a compiler listing, such that a debugger that
does not support the DWARF format, such as debugger 150, extracts
debugging information from the compiler listing. A compiler listing
may include the following information: assigned offsets into the
object program for each source line, in order to determine which
source line is being executed when the program malfunctions; a
symbol table that includes information about variable declarations
and assigned addresses in storage for variables; and
cross-reference information that includes information indicating
which variable(s) are referenced on each source line. In some
embodiments, debugging data converter 140 converts DWARF debugging
data into a compiler listing that is human-readable. Debugging data
converter 140 may store the generated compiler listing to a
repository, such as debugging data repository 130. In one
embodiment, debugging data converter 140 resides on server 20. In
another embodiment, debugging data converter 140 may reside on
another server or another computing device, provided that debugging
data converter 140 has access to debugging data repository 130.
[0018] Debugger 150 is a debugger that does not support the DWARF
debugging data format. In embodiments of the present invention,
debugger 150 supports the compiler listing generated by debugging
data converter 140. A debugger is used to test and debug other
programs. In one embodiment, debugger 150 resides on server 20. In
another embodiment, debugger 150 may reside on another server or
another computing device, provided that debugger 150 has access to
debugging data repository 130.
[0019] FIG. 2 depicts a flowchart of the steps of debugging data
converter 140 executing within the computing system of FIG. 1, in
accordance with an embodiment of the present invention. Debugging
data converter 140 operates to receive DWARF debugging data,
generated by compiler 120 using source code 110, and convert it
into a compiler listing format, such that a debugger incompatible
with the DWARF format, such as debugger 150, may consume the
compiler listing provide source-level debugging of source code
110.
[0020] In one embodiment, initially, a user may write source code,
such as source code 110. Source code 110 may be any generic source
code written in any one of a number of computer programming
languages, such as C++, Smalltalk, or COBOL. Source code 110 may be
compiled by compiler 120. Compiler 120 may be any compiler capable
of generating DWARF debugging data during compilation of source
code 110. In some embodiments, compiler 120 may store generated
DWARF data to a repository, such as debugging data repository
130.
[0021] In step 205, debugging data converter 140 receives DWARF
debugging data. In some embodiments, debugging data converter 140
receives DWARF debugging data from a compiler, such as compiler
120. In other embodiments, debugging data converter 140 accesses
and retrieves DWARF debugging data from a repository, such as
debugging data repository 130. In still other embodiments,
debugging data converter 140 is a function of debugger 150, such
that debugging data converter 140 can convert DWARF debugging data
into a debugging data format debugger 150 can comprehend.
[0022] In step 210, debugging data converter 140 extracts source
lines from the DWARF debugging data. DWARF debugging data is
organized into blocks. Each block may contain information related
to one or more source lines of source code 110. In some
embodiments, debugging data converter 140 extracts each source line
from each block and assigns each extracted source line a sequential
line number. In some embodiments, debugging data converter 140
differentiates line numbers via a newline character. A newline
character is a special character or sequence of characters
signifying the end of a line of text. In some embodiments,
debugging data converter 140 uses an application programming
interface (API) to extract each source line. An API is a set of
routines, protocols, and tools for building software applications
by specifying how software components should interact. In some
embodiments, APIs used by debugging data converter 140 are
published as an open standard for UNIX.RTM..
[0023] In step 215, debugging data converter 140 builds a verbcode
table. A verbcode table is a table including each verb associated
with source code 110, as deciphered from the DWARF debugging data,
along with one or more reference lines associated with each
respective verb. A verb, in the present context, is a grammatical
verb indicating an action to be taken within the computing
language. For example, IF, ADD, READ, WRITE, are each verbs. In
some embodiments, the verbcode table is organized alphabetically
according to verb. In other embodiments, the verbcode table may be
organized in another manner.
[0024] In step 220, debugging data converter 140 extracts the data
name and definition line, for each variable of source code 110,
from the DWARF debugging data. DWARF debugging data comprises
multiple debugging information entries (DIEs). Each DIE has a tag,
which specifies what the DIE describes and a list of attributes,
which fill in details and further describes the entity. DIE
attributes may contain a variety of values such as constants (such
as a function name), variables (such as the start address for a
function), or references to another DIE (such as for the type of a
function's return value). In some embodiments, debugging data
converter 140 accesses each variable DIE (i.e., DW_TAG_variable)
and retrieves, from each variable DIE, the respective definition
line, or declaration line, and data name of the variable. In some
embodiments, the declaration line is an attribute, included within
the field DW_AT_decl_line, and the data name is an attribute
included within the field DW_AT_name. In some embodiments,
debugging data converter 140 may extract data name and definition
line information for each variable through the use of one or more
APIs.
[0025] In step 225, debugging data converter 140 builds a table of
references. In embodiments of the present invention, debugging data
converter 140 initially builds a reference list by accessing
applicable information stored within the DWARF debugging data. In
embodiments of the present invention, a reference list includes
each variable, along with each respective line, of source code 110
within which the variable is referenced. In some embodiments,
debugging data converter 140 may further identify source fragments
which locate the parts of the source line that reference each
particular variable. The DIE for a variable may include a DIE
attribute indicating a list of source coordinates (i.e., row,
column) where the variable is referenced. Debugging data converter
140 may use an identified row to identify a line of source code
where the variable is referenced. In some embodiments, debugging
data converter 140 may use a column as a parsing start position, if
further info regarding the variable's use was needed.
[0026] Using the retrieved source fragments, debugging data
converter 140 may create a table to facilitate locating a fragment
according to variable name. Debugging data converter 140 may
additionally determine whether each variable referenced in each
source fragment is modified. Using the source coordinates where the
variable is referenced, debugging data converter 140 can access the
source fragments for the variable. Data debugging converter 140 can
match the row and variable name to an indicated DIE location at an
offset, where a DIE attribute indicates whether the variable in
question is modified. This process can be used for each location
the variable is referenced. In some embodiments, if debugging data
converter 140 determines that a variable referenced in a source
fragment is modified, debugging data converter 140 annotates the
reference line of the source fragment within the table of variable
references to indicate a location where the variable may be
modified. In some embodiments, the annotation is an "M" in from of
the reference line. In some embodiments, debugging data converter
140 may determine the location in which each variable is referenced
in source code 110, and whether or not the source code line
modifies the each respective variable, using one or more APIs.
[0027] In step 230, debugging data converter 140 builds a symbol
table. In embodiments of the present invention, a symbol table
includes information such as data names and associated structure
hierarchy information, base locator information, and/or assembler
data definition information. In some embodiments, debugging data
converter 140 retrieves a list of variables and associated
structure hierarchy for each variable. Debugging data converter 140
may determine variable structure hierarchy by accessing children or
sibling DIEs related to a base DIE. In some embodiments, debugging
data converter 140 may further collect base type info used to
formulate a declaration or definition. A base type is the type of a
unit of data, such as an array. In some embodiments, for example
when source code 110 was written in the COBOL programming language,
debugging data converter 140 extract information, such as base
locator information, from the DWARF debugging data that relates to
the data division section of the COBOL program. The data division
is the part of a COBOL program in which the format and layout of
external files and databases, and internally-used variables and
constants are defined. In some embodiments, debugging data
converter 140 further accesses a location list of addressing
expressions within the DWARF debugging data, and processes the
expressions to determine an offset of the respective variable or
structure member. In some embodiments, debugging data converter 140
accesses information necessary to build the symbol table using one
or more APIs.
[0028] In step 235, debugging data converter 140 builds an offset
listing from information retrieved from the DWARF debugging data.
An offset listing includes verbs, such as the verbs discussed in
reference to step 215, along with the line number from the source
code and the line offset value. The line offset value indicates the
offset, from the start of the program (i.e., source code 110), of
the code generated for the respective verb. In some embodiments,
the offset value will be in hexadecimal notation. In some
embodiments, debugging data converter 140 may gather line number
information and line offset information using one or more APIs.
[0029] In step 240, debugging data converter 140 generates a static
and/or automatic map using information extracted from the DWARF
debugging data. Each map may provide variable addressing. A static
map lists all static variables and is sorted by hexadecimal offset.
An automatic map lists, for each block of the DWARF debugging data,
all automatic variables sorted by hex offset. In some embodiments,
debugging data converter 140 may gather offset information using
one or more APIs, and information from the generated symbol
table.
[0030] FIG. 3 depicts a block diagram of components of server 20 in
accordance with an illustrative embodiment of the present
invention. It should be appreciated that FIG. 3 provides only an
illustration of one implementation and does not imply any
limitations with regard to the environments in which different
embodiments may be implemented. Many modifications to the depicted
environment may be made.
[0031] Server 20 includes communications fabric 302, which provides
communications between computer processor(s) 304, memory 306,
persistent storage 308, communications unit 310, and input/output
(I/O) interface(s) 312. Communications fabric 302 can be
implemented with any architecture designed for passing data and/or
control information between processors (such as microprocessors,
communications and network processors, etc.), system memory,
peripheral devices, and any other hardware components within a
system. For example, communications fabric 302 can be implemented
with one or more buses.
[0032] Memory 306 and persistent storage 308 are computer readable
storage media. In this embodiment, memory 306 includes random
access memory (RAM) 314 and cache memory 316. In general, memory
306 can include any suitable volatile or non-volatile computer
readable storage media.
[0033] Source code 110, compiler 120, debugging data repository
130, debugging data converter 140, and debugger 150 are stored in
persistent storage 308 for execution and/or access by one or more
of the respective computer processors 304 via one or more memories
of memory 306. In this embodiment, persistent storage 308 includes
a magnetic hard disk drive. Alternatively, or in addition to a
magnetic hard disk drive, persistent storage 308 can include a
solid state hard drive, a semiconductor storage device, read-only
memory (ROM), erasable programmable read-only memory (EPROM), flash
memory, or any other computer readable storage media that is
capable of storing program instructions or digital information.
[0034] The media used by persistent storage 308 may also be
removable. For example, a removable hard drive may be used for
persistent storage 308. Other examples include optical and magnetic
disks, thumb drives, and smart cards that are inserted into a drive
for transfer onto another computer readable storage medium that is
also part of persistent storage 308.
[0035] Communications unit 310, in these examples, provides for
communications with other data processing systems or devices. In
these examples, communications unit 310 includes one or more
network interface cards. Communications unit 310 may provide
communications through the use of either or both physical and
wireless communications links. Source code 110, compiler 120,
debugging data repository, debugging data converter 140, and
debugger 150 may be downloaded to persistent storage 308 through
communications unit 310.
[0036] I/O interface(s) 312 allows for input and output of data
with other devices that may be connected to server 20. For example,
I/O interface 312 may provide a connection to external devices 318
such as a keyboard, keypad, a touch screen, and/or some other
suitable input device. External devices 318 can also include
portable computer readable storage media such as, for example,
thumb drives, portable optical or magnetic disks, and memory cards.
Software and data used to practice embodiments of the present
invention, e.g., source code 110, compiler 120, debugging data
repository 130, debugging data converter 140, and debugger 150, can
be stored on such portable computer readable storage media and can
be loaded onto persistent storage 308 via I/O interface(s) 312. I/O
interface(s) 312 also connect to a display 320.
[0037] Display 320 provides a mechanism to display data to a user
and may be, for example, a computer monitor.
[0038] The programs described herein are identified based upon the
application for which they are implemented in a specific embodiment
of the invention. However, it should be appreciated that any
particular program nomenclature herein is used merely for
convenience, and thus the invention should not be limited to use
solely in any specific application identified and/or implied by
such nomenclature.
[0039] The present invention may be a system, a method, and/or a
computer program product. The computer program product may include
a computer readable storage medium (or media) having computer
readable program instructions thereon for causing a processor to
carry out aspects of the present invention.
[0040] The computer readable storage medium can be a tangible
device that can retain and store instructions for use by an
instruction execution device. The computer readable storage medium
may be, for example, but is not limited to, an electronic storage
device, a magnetic storage device, an optical storage device, an
electromagnetic storage device, a semiconductor storage device, or
any suitable combination of the foregoing. A non-exhaustive list of
more specific examples of the computer readable storage medium
includes the following: a portable computer diskette, a hard disk,
a random access memory (RAM), a read-only memory (ROM), an erasable
programmable read-only memory (EPROM or Flash memory), a static
random access memory (SRAM), a portable compact disc read-only
memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a
floppy disk, a mechanically encoded device such as punch-cards or
raised structures in a groove having instructions recorded thereon,
and any suitable combination of the foregoing. A computer readable
storage medium, as used herein, is not to be construed as being
transitory signals per se, such as radio waves or other freely
propagating electromagnetic waves, electromagnetic waves
propagating through a waveguide or other transmission media (e.g.,
light pulses passing through a fiber-optic cable), or electrical
signals transmitted through a wire.
[0041] Computer readable program instructions described herein can
be downloaded to respective computing/processing devices from a
computer readable storage medium or to an external computer or
external storage device via a network, for example, the Internet, a
local area network, a wide area network and/or a wireless network.
The network may comprise copper transmission cables, optical
transmission fibers, wireless transmission, routers, firewalls,
switches, gateway computers and/or edge servers. A network adapter
card or network interface in each computing/processing device
receives computer readable program instructions from the network
and forwards the computer readable program instructions for storage
in a computer readable storage medium within the respective
computing/processing device.
[0042] Computer readable program instructions for carrying out
operations of the present invention may be assembler instructions,
instruction-set-architecture (ISA) instructions, machine
instructions, machine dependent instructions, microcode, firmware
instructions, state-setting data, or either source code or object
code written in any combination of one or more programming
languages, including an object oriented programming language such
as Smalltalk, C++ or the like, and conventional procedural
programming languages, such as the "C" programming language or
similar programming languages. The computer readable program
instructions may execute entirely on the user's computer, partly on
the user's computer, as a stand-alone software package, partly on
the user's computer and partly on a remote computer or entirely on
the remote computer or server. In the latter scenario, the remote
computer may be connected to the user's computer through any type
of network, including a local area network (LAN) or a wide area
network (WAN), or the connection may be made to an external
computer (for example, through the Internet using an Internet
Service Provider). In some embodiments, electronic circuitry
including, for example, programmable logic circuitry,
field-programmable gate arrays (FPGA), or programmable logic arrays
(PLA) may execute the computer readable program instructions by
utilizing state information of the computer readable program
instructions to personalize the electronic circuitry, in order to
perform aspects of the present invention.
[0043] Aspects of the present invention are described herein with
reference to flowchart illustrations and/or block diagrams of
methods, apparatus (systems), and computer program products
according to embodiments of the invention. It will be understood
that each block of the flowchart illustrations and/or block
diagrams, and combinations of blocks in the flowchart illustrations
and/or block diagrams, can be implemented by computer readable
program instructions.
[0044] These computer readable program instructions may be provided
to a processor of a general purpose computer, special purpose
computer, or other programmable data processing apparatus to
produce a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or blocks.
These computer readable program instructions may also be stored in
a computer readable storage medium that can direct a computer, a
programmable data processing apparatus, and/or other devices to
function in a particular manner, such that the computer readable
storage medium having instructions stored therein comprises an
article of manufacture including instructions which implement
aspects of the function/act specified in the flowchart and/or block
diagram block or blocks.
[0045] The computer readable program instructions may also be
loaded onto a computer, other programmable data processing
apparatus, or other device to cause a series of operational steps
to be performed on the computer, other programmable apparatus or
other device to produce a computer implemented process, such that
the instructions which execute on the computer, other programmable
apparatus, or other device implement the functions/acts specified
in the flowchart and/or block diagram block or blocks.
[0046] The flowchart and block diagrams in the Figures illustrate
the architecture, functionality, and operation of possible
implementations of systems, methods, and computer program products
according to various embodiments of the present invention. In this
regard, each block in the flowchart or block diagrams may represent
a module, segment, or portion of instructions, which comprises one
or more executable instructions for implementing the specified
logical function(s). In some alternative implementations, the
functions noted in the block may occur out of the order noted in
the figures. For example, two blocks shown in succession may, in
fact, be executed substantially concurrently, or the blocks may
sometimes be executed in the reverse order, depending upon the
functionality involved. It will also be noted that each block of
the block diagrams and/or flowchart illustration, and combinations
of blocks in the block diagrams and/or flowchart illustration, can
be implemented by special purpose hardware-based systems that
perform the specified functions or acts or carry out combinations
of special purpose hardware and computer instructions.
* * * * *