How to consistently organize code for debugging? - debugging

When working in a big project that requires debugging (like every project) you realize how much people love "printf" before the IDE's built-in debugger. By this I mean
Sometimes you need to render variable values to screen (specially for interactive debugging).
Sometimes to log them in a file
Sometimes you have to change the visibility (make them public) just to another class to access it (a logger or a renderer for example).
Some other times you need to save the previous value in a member just to contrast it with the new during debugging
...
When a project gets huge with a lot of people working on it, all this debugging-specific code can get messy and hard to differentiate from normal code. This can be crazy for those who have to update/change someone else's code or to prepare it for a release.
How do you solve this?
It is always good to have naming standards and I guess that debug-coding standards should be quite useful (like marking every debug-variable with a _DBG sufix). But I also guess naming is just not enough. Maybe centralizing it into a friendly tracker class, or creating a robust base of macros in order to erase it all for the release. I don't know.
What design techniques, patterns and standards would you embrace if you are asked to write a debug-coding document for all others in the project to follow?
I am not talking about tools, libraries or IDE-specific commands, but for OO design decisions.
Thanks.


Don't commit debugging code, just debuggin tools.
Loggin OTOH has a natural place in execption handling routines and such. Also a few well placed logging statments in a few commonly used APIs can be good for debugging.
Like one log statment to log all SQL executed from the system.


My vote would be with what you described as a friendly tracker class. This class would keep all of that centralized, and potentially even allow you to change debug/logging strategies dynamically.
I would avoid things like Macros simply because that's a compiler trick, and not true OO. By abstracting the concept of debug/logging, you have the opportunity to do lots of things with it including making it a no-op if needed.


Logging or debugging? I believe that well-designed and properly unit-tested application should not need to be permanently instrumented for debugging. Logging on the other hand can be very useful, both in finding bugs and auditing program actions. Rather than cover a lot of information that you can get elsewhere, I would point you at logging.apache.org for either concrete implementations that you can use or a template for a reasonable design of a logging infrastructure.


I think it's particularly important to avoid using System.outs / printfs directly and instead use (even a custom) logging class. That at least gives you a centralized kill-switch for all the loggings (minus the call costs in Java).
It is also useful to have that log class have info/warn/error/caveat, etc.
I would be careful about error levels, user ids, metadata, etc. since people don't always add them.
Also, one of the most common problems that I've seen is that people put temporary printfs in the code as they debug something, and then forget where they put them. I use a tool that tracks everything that I do so I can quickly identify all my recent edits since an abstract checkpoint and delete them. In most cases, however, you may want to pose special rules on debug code that can be checked into your source control.


In VB6 you've got
Debug.Print
which sends output to a window in the IDE. It's bearable for small projects. VB6 also has
#If <some var set in the project properties>
'debugging code
#End If
I have a logging class which I declare at the top with
Dim Trc as Std.Traces
and use in various places (often inside #If/#End If blocks)
Trc.Tracing = True
Trc.Tracefile = "c:\temp\app.log"
Trc.Trace 'with no argument stores date stamp
Trc.Trace "Var=" & var
Yes it does get messy, and yes I wish there was a better way.


We routinely are beginning to use a static class that we write trace messages to. It is very basic and still requires a call from the executing method, but it serves our purpose.
In the .NET world, there is already a fair amount of built in trace information available, so we do not need to worry about which methods are called or what the execution time is. These are more for specific events which occur in the execution of the code.
If your language does not support, through its tracing constructs, categorization of messages, it should be something that you add to your tracing code. Something to the effect that will identify different levels of importance and/or functional areas is a great start.


Just avoid instrumenting your code by modifying it. Learn to use a debugger. Make logging and error handling easy. Have a look at Aspect Oriented Programming


Debugging/Logging code can indeed be intrusive. In our C++ projects, we wrap common debug/log code in macros - very much like asserts. I often find that logging is most usefull in the lower level components so it doesn't have to go everywhere.
There is a lot in the other answers to both agree and disagree with :) Having debug/logging code can be a very valuable tool for troubleshooting problems. In Windows, there are many techniques - the two major ones are:
Extensive use of checked (DBG) build asserts and lots of testing on DBG builds.
the use of ETW in what we call 'fre' or 'retail' builds.
Checked builds (what most ohter call DEBUG builds) are very helpfull for us as well. We run all our tests on both 'fre' and 'chk' builds (on x86 and AMD64 as well, all serever stuff runs on Itanium too...). Some people even self host (dogfood) on checked builds. This does two things
Finds lots of bugs that woldn't be found otherwise.
Quickly elimintes noisy or unnessary asserts.
In Windows, we use Event Tracing for Windows (ETW) extensively. ETW is an efficient static logging mechanism. The NT kernel and many components are very well instrumented. ETW has a lot of advantages:
Any ETW event provider can be dynamically enabled/disabled at run time - no rebooting or process restarts required. Most ETW providers provide granular control over individual events, or groups of events.
Events from any provider (most importantly the kernel) can be merged into a single trace so all events can be correlated.
A merged trace can be copied off the box and fully processed - with symbols.
The NT kernel sample pofile interrupt can generate an ETW event - this yeilds a very light weight sample profiler that can be used any time
On Vista and Windows Server 2008, logging an event is lock free and fully multi-core aware - a thread on each processor can independently log events with no synchronization needed between them.
This is hugly valuable for us, and can be for your Windows code as well - ETW is usuable by any component - including user mode, drivers and other kernel components.
One thing we often do is write a streaming ETW consumer. Instead of putting printfs in the code, I just put ETW events at intersting places. When my componetn is running, I can then just run my ETW watcher at any time - the watcher receivs the events and displays them, conts them, or does other interesting things with them.
I very much respectfully disagree with tvanfosson. Even the best code can benefit from well implemented logging. Well implimented static run-time logging can make finding many problems straight forward - without it, you have zero visiblilty into what is happening in your component. You can look at inputs, outputs and guess -that's about it.
They key here is the term 'well implimented'. Instrumentation must be in the right place. Like any thing else, this requries some thought and planning. If it is not in helpfull/intersting places, then it will not help you find problems in a a development, testing, or deployed scenario. You can also have too much instrumeation causing perf problems when it is on - or even off!
Of course, different software products or componetns will have different needs. Some things may need very little instrumenation. But a widely depolyed or critical component can greatly benefit from weill egineered instrumeantion.
Here is a scenario for you (note, this very well may not apply to you...:) ). Lets say you have a line-of-business app deployed on every desktop in your company - hundreds or thousands of users. What do you do when someone has a pbolem? Do yo stop by their office and hookup a debugger? If so, how do you know what version they have? Where do you get the right symbols? How do you get the debuger on their system? What if it only happens once every few hours or days? Are you going to let the system run with the debugger connected all that time?
As you can imagine - hooking up debugger in this scenario is disruptive.
If your component is instrumented with ETW, then you could ask your user to simply turn on tracing; continue to do his/her work; then hit the "WTF" button when the problem happens. Even better: your app may have be able to self log - detecting problems at run time and turning on logging auto-magicaly. It could even send you ETW files when problems occured.
These are just simple exmples - logging can be handled many different ways. My key recomendation here is to think about how loging might be able to help you find, debug, and fix problems in your componetns at dev time, test time, and after they are deployed.


I was burnt by the same issue in about every project I've been involved with, so now I have this habit that involves extensive use of logging libraries (whatever the language/platform provides) from the start. Any Log4X port is fine for me.


Building yourself some proper debug tools can be extremely valuable. For example in a 3D environment, you might have an option to display the octree, or to render planned AI paths, or to draw waypoints that are normally invisible. You'd probably also want some on-screen display to aid with profiling too: the current framerate, count of polygons on screen, texture memory usage, and so on.
Although this takes some time and effort to do, in the long run it can save you a lot of time and frustration.

Related

Why isn't there a widely used tool to "warmup" .NET applications to prevent "cold start"?

I understand why cold starts happen (Byte code needs to be turned into machine code through JIT compilation). However with all the generated meta data available for binaries these days I do not understand why there isn't a simple tool that automatically takes the byte code and turns ALL PATHS THROUGH THE CODE (auto discovered) into machine code specific for that target platform. That would mean the first request through any path (assume a rest api) would be fast and not require any further Just In Time Compilation.
We can create an automation test suite or load test to JIT all the paths before allowing the machine into the load balancer rotation (good best practice anyway). We can also flip the "always on" setting in cloud hosting providers to keep the warmed application from getting evicted from memory (requiring the entire process over again). However, it seems like such an archaic process to still be having in 2020.
Why isn't there a tool that does this? What is the limitation that prevents us from using meta data, debug symbols and/or other means to understand how to generate machine code that is already warm and ready for users from the start?

So I have been asking some sharp minds around my professional network and no one seems to be able to point out exactly what limitation makes this so hard to do. However, I did get a few tools on my radar that do what i'm looking for to some level.
Crossgen appears to be the most promising but it's far from widely used among the many peers I've spoken to. Will have to take a closer look.
Also several do some sort of startup task that runs some class initialization and also register them as singletons. I wouldn't consider those much different then just running integration or load tests on the application.

Most programming languages have some form of native image compiler tool. It's up to you to use them if that is what you are looking to do.
Providers are supposed to give you a platform for your application and there is a certain amount of isolation and privacy you should expect from your provider. They should not go digging into your application to figure out all its "paths". That would be very invasive.
Plus "warming up" all paths would be an overly resource intensive process for a provider to be obligated to perform for every application they host.

Better Breakpoints for Multi-Client Development

My development system uses different clients for development and testing which I assume is a common practice. Unfortunately this introduces a rather annoying convenience issue when it comes to debugging. While breakpoints placed on the development system will stick to their code and move as lines are inserted or deleted, this is rather obviously not the case for breakpoints placed on the same code in another client.
Since the system has no knowledge of exactly how rows were changed between two versions, breakpoints placed in the testing client will remain at a particular line in the program. Any change to the code will therefore break the breakpoints. To resolve this I have to: open another program or screen then return to the program to refresh the code (where's the refresh button SAP?), find where the breakpoints have been moved to and remove them one-by-one (where's the batch remove breakpoints button SAP?) and then set new breakpoints at usually the exact same location.
This problem is becoming so frequent in my work that I sometimes spend more time moving breakpoints than I spend on the actual development. In some cases I just gave up and started coding in user breakpoints since those will at least remain in place. However, these come with their own drawbacks as they can't be removed in the debugger, making them useless when you are forced to stop at every breakpoint in a thousand-record loop.
My actual question is now whether there's a better approach or best practice when it comes to debugging in this scenario. I'm relatively new to ABAP programming so I hope that more experienced developers have alternatives or tricks that they use to speed this process up. Is there some better way to go about debugging and breaking code in a secondary client?

You could try creating a checkpoint group in transaction SAAB, and code the break-points to the checkpoint group.
Syntax
BREAK-POINT ID zyour_new_checkpoint_group.
This has the advantage that you can activate it for a set time, or a set of users etc. However, I'm not sure that if you get stuck in a 1000-line loop that you will be able to just deactivate it & skip over the break-point.
It may be worthwhile to check first if you can deactivate the checkpoint group on the fly while the program is running before using this in anger.

The practice of having a development client and test client makes sense for client dependent objects, e.g. customizing. It ensures a reasonably stable environment for development testing. But it makes no sense for programs and other development objects since they are client independent. However, it is still important that all your client dependent development objects (e.g. standard texts and SapScripts) originate from the development client so it is best to create all your objects there. But once you have done that and are on to testing and debugging there is no technical reason to not just change your program in the test client.
It might take some effort to convince the people responsible for development procedures of this practice since there always is a chance that objects get created in the wrong client which could lead to a mess when you want to release them. But with the scenario you describe in your question you should be able to plead your case.

Intercept BIG application execution after DLL injection

I must intercept execution in very big application in many places.
What programs I can use to do this? What techniques exists for this problems?
Manually reverse engineering and adding hooks is maybe not optimal solution for this problem, because application is very big and some part of application can be updated in some time, i think with some tools or good practices for this problem i can do this faster, anyone know how to do?
Anybody help me?

seeing as the tools part has been covered, here is something for the techniques.
Depending what it is you need to hook and whether or not there is protection invloved, there are a few methods:
Relative call/jmp patching in the virtualized binary: this is the simplest, but also a lot of work if you can't automatically find all references to a function, this probably won't work in this cause due to your criteria.
IAT/EAT hooking: this is use for imports(IAT) and exports(EAT), great if your targeting a known importted/exported set of API functions. a good example of this can be found here or here
Hot-Patching: Windows XP SP2 introduced something called "hot-patching" (used for realtime system function updates), where all its (the WinAPI) functions start with a 'mov edi,edi', allowing a relative jump to be patched into the free space created above every hot-patchable function(one can do it too). this is generally used for programs that checksum there IAT's or have other funny forms of protection, more info can be found here and here
Code-Caving: capturing execution flow by placing redirections in arbitrary code space. see here, here or here
VFT/COM Redirection: basically overwriting entries in a objects virtual function table, useful for OOP/COM based applications. see this
There are a lot of 3rd party libraries, most famous would probably be MS Detours, one can also look at APIHijack or a mini-hook engine.
Ofcourse nothing can substitute for the initial poking you'll need to do with a debugger like ollydbg, but knowing the method your gonna use can drastically short them amount time time spent poking around

Some details on what exactly you need to do (e.g. how do you determine where to break) would be nice. Depending on your situation, something like Pin might work.

I suggest using Deviare API Hook. It's the easiest way you can do what you need. It has some COM objects that you can use to hook an application from a different process. In your process you get full parameter information and you can use it in any programming language (I'm using C# and it works like a charm).
If you need to intercept registry API I suggest using Deviare to debug what you need to intercept but then you will have to make your own hooks, otherwise, you'll find performance issues.

You can do API Hooking if you are interested in intercepting method calls.
Or use some disassembler like softice or ollydbg or win32dasm.

"Works on my machine" - How to fix non-reproducible bugs?

Very occasionally, despite all testing efforts, I get hit with a bug report from a customer that I simply can't reproduce in the office.
(Apologies to Jeff for the 'borrowing' of the badge)
I have a few "tools" that I can use to try and locate and fix these, but it always feels a bit like I'm knife-and-forking it:-
Asking for more and more context from the customer: (systeminfo)
Log files from our application
Ad-hoc tests with the customer to attempt to change the behaviour
Providing customer with a new build with additional diagnostics
Thinking about the problem in the bath...
Site visit (assuming customer is somewhere warm and sunny)
Are there set procedures, or other techniques than anyone uses to resolve problems like this?

One of the attributes of good debuggers, I think is that they always have a lot of weapons in their toolkit. They never seem to get "stuck" for too long and there is always something else for them to try. Some of the things I've been known to do:
ask for memory dumps
install a remote debugger on a client machine
add tracing code to builds
add logging code for debugging purposes
add performance counters
add configuration parameters to various bits of suspicious code so I can turn on and off features
rewrite and refactor suspicious code
try to replicate the issue locally on a different OS or machine
use debugging tools such as application verifier
use 3rd party load generation tools
write simulation tools in-house for load generation when the above failed
use tools like Glowcode to analyse memory leaks and performance issues
reinstall the client machine from scratch
get registry dumps and apply them locally
use registry and file watcher tools
Eventually, I find the bug just gives up out of some kind of awe at my persistence. Or the client realises that it's probably a machine or client side install or configuration issue.

Extensive logging usually helps.

The easiest way is always to see the customer in action (assuming that its readily reproducible by the customer). Oftentimes, problems arise due to issues with the customer's computer environment, conflicts with other programs, etc - these are details which you will not be able to catch on your dev rig. So a site visit might be useful; but if that's not convenient, tools like RealVNC might help as well in letting you see the customer 'do their thing'.
(watching the customer in action also allows you to catch them out in any WTF moments that they might have)
Now, if the problem is intermittent, then things get somewhat more complicated. The best way to get around this problem would be to log useful information in places where you guess problems could occur and perhaps use a tool like Splunk to index the log files during analysis. A diagnostic build (i.e. with extra logging) might be useful in this case.

I'm just in the middle of implementing an automated error reporting system that sends back to me information (currently via email although you could use a webservice) from any exception encountered by the app.
That way I get (nearly) all the information that I would do if I was sitting in front of VS2008 and it really helps me to work out what the problem is.
The customers are also usually (sorta) impressed that I know about their problem as soon as they encounter it!
Also, if you use the Application.ThreadException error handler you can send back info on unexpected exceptions too!

We use all the methods you mention progressively starting with the easiest and proceeding to the harder.
However you forget that sometimes hardware is at fault. For example, memory could be malfunctioning and some computation-intensive code will behave strangely throwing exceptions with weird diagnostics. Of cource, it works on your machine, since you don't have faulty hardware.
Experience is needed to identify such errors and insist that customer tries to install the program on another machine or does hardware check. One thing that helps greatly is good error handling - when your code throws an exception it should provide details, not just indicate that something is bad. With good error indication it's easier to identify such suspicious issues related to faulty hardware.

I think one of the most important things is the ability to ask sensible questions around what the customer has reported... More often than not they're not mentioning something that they don't see as relevant, but is actually key.
Telepathy would also be useful...

We've had good success using EurekaLog with it posting directly to FogBugz. This gets us a bug report containing a call stack, along with related system info (other processes running, memory, network details etc) and a screen shot. Occasionally customers enter further info too, which is helpful. It's certainly, in most cases, made it much easier and quicker to fix bugs.

One technique I've found useful is building an application with an integrated "diagnostic" mode (enabled by a command line switch when you launch the app). That certainly avoids the need to create custom builds with additional logging.
Otherwise, it sounds like what you're doing is as good an approach as any.

Copilot (assuming customer is somewhere cold and rainy :)

The usual procedure for this is to expect something like this will happen and add a ton of logging information. Of course you don't enable it from the beginning, but only when this happens.
Usually customers don't like to have to install a new version or some diagnostic tools. It is not their job to do your debugging. And visiting a client for cases like these is rarely an option. You must involve the client as little as possible. Changing a switch and sending you a log file is OK - anything more than this is too much.
I like the alternative of thinking the problem at the bath. I will start from trying to find out the differences between my machine and the client's configuration.

As a software engineer doing webstuff (booking/shop/member systems etc) the most important thing for us is to get as much information from the customer as possible.
Going from
it's broke!
to
it's broke! & here are screenshots of
every option I picked whilst
generating this particular report
reduces the amount of time it takes us to reproduce and fix an issue no end.
It may be obvious, but it takes a fair amount of chasing to get this kind of information from our customers sometimes! But it's worth it just for those moments you find they're not actually doing what they say they are.

I had these problems also. My solution was to add lots of logging and give the customer a debug build with all the possible debug information. Then make sure dr Watson (it was on Windows NT) created a memory dump with enough information.
After loading the memory dump in the debugger I could find out where and why it crashed.
EDIT: Oh, this obviously only works if the application terminates violently...

I think following the trail of the actions user took can lead us to the reasons of failure or selective failures. But most of the times users are at loss to precisely describe the interactions with the applications, the automatic screenshot taking (if it is desktop app. for .net app you can check Jeff's UnhandledExceptionHandler). Logging all the important action which change state of the objects can also help us in understanding it.

I don't have this problem very often, but if I did, I would use a screen sharing or recorded application to watch the user in action without having to go there (unless, as you said, it's warm and sunny and the company pays the trip).

I have recently been investigating such an issue myself. Over the course of my carrier I have learnt that, while computer systems may be complex, they are predictable so have faith that you can find the problem. My approach to these kinds of issues two fold:
1) Gather as much detailed information as possible from the customer about their failure and analyse it meticulously for patterns. Gather multiple sets of data for multiple failure occurrences to build up a clearer picture.
2) Try and reproduce the failure in house. Continue to make your system more and more similar to the customers system until you can reproduce it, the system is identical or it becomes impractical to make it more similar.
While doing this consider:
1)What differences exist between this system and other working systems.
2)What has recently changed in your product or the customers configuration that has caused the problem to start occurring.
Regards

Depending on the issue you could get WinDbg dumps, they normally give a pretty good idea of what is going on. We have diagnosed quite a few problems that weren't crashed from minidumps.
For .Net apps we also was Trace.Writeline then we can get the user to fire up DbgView and send us the output.

Its very complicated issue . I was thinking writing some procedure for this . I just made some procedure for this non-reproducible bug . it might be helpful
When the Bug accorded .. There are several factors it might to occur.
I am Sure all bugs are reproducible . I always keep eye for these kind of issues..
Get the System Information
what other process the customer did before that.
Time period it occurs . its rare or frequent
its next action happened after the issue ( its always same or different )
Find the factors for this bug ( as developer )
Find the exact position where this issue happened .
Find ALL THE SYSTEM Factors on that time
check all memory leaks or user error issue or wrong condition in code
List out all facotrs to may cause this issue.
How the each factors are affected this and wat are the data is holding those factors
Check memeory issues happened
check the customer have the current update code like yours
check all log from atleast 1 month and find any upnormal operation happened . keep on note

Just a short anecdote (hence 'community wiki'): Last week I thought it was a clever idea in a Django app to import the module pprint for pretty printing Python data only if DEBUG was True:
if settings.DEBUG:
from pprint import pprint
Then I used here and there the pprint command as debugging statement:
pprint(somevar) # show somevar on the console
After finishing the work, I tested the app with setting DEBUG=False. You can guess what happened: The site broke with HTTP500 errors all over the place, and I did not know why, because there is no traceback if DEBUG is False. I was puzzled that the errors disappeared magically, if I switched back to debug mode.
It took me 1-2 hours of putting print statements all over the code to find that the code crashes at exactly the above pprint() line. Then it took me another half an hour to convince myself to stop banging my head on the table.
Now comes the moral of the story:
Not every thing that looks like a clever idea in the first view is such savvy in the end.
An important point to look at for debugging these errors are all configuration options and platform switches your code by itself makes. This can be quite a lot more than just some user preferences. Document good, if you make an assumption about the user's platform (e.g., if you test for Win/Mac/Linux only, will your code crash on BSD or Solaris?)
Cheers,

However tough a non-reproducible problem is - we can still have a structured and strategic approach to solve them - and I can say through experience that it requires out of box thinking in 50% of the cases. Generally speaking, one can categorize the problems into different types which helps to identify what tool to be used. For example if you have a non-reproducible application crash issue or a memory issue you can use profilers and nail down the issue caused in the particular functionality.
Also, one of the most important approach is inforamation rich logging. I also use a lot of enums to describe the state of the process depending on the scenario in question. for exampe, I used like Initiated, Triggered, Running, Waiting Repaired etc to describe the schedules states and saved them to DB at different stages.

Not mentioned yet, but "directed code review" is one good solution, especially if you didn't do a proper review (at least 1 hour per 100 lines of code) before release.
I have also seen impressive demos of AppSight Suite, which is basically an advanced environment monitoring and logging tool. It allows the customer to record what happens on his machine in an extensive but fairly compact log file which you can then replay.

As many have mentioned, extensive logging, and asking the client for the log files when something goes wrong. In addition, as I worked more with web apps, I'll also provide detailed, but succinct deployment documentation (e.g., deployment steps, environmental resources that need to be set up etc).
Here are common problems I've seen that lead to the types of problem you are describing:
Environment not set up properly (e.g., missing environment variables, data sources etc).
Application not fully deployed (e.g., database schema not deployed).
Difference in operating system configuration (default character encoding being the most common culprit for me).
Most of the time, these issues can be identified through the log content.

You can use tools like Microsoft SharedView or TeamViewer to connect to remote PC and inspect problem directly on site. Of course, you'll need cooperation with customer.

Why is debugging better in an IDE? [closed]

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I've been a software developer for over twenty years, programming in C, Perl, SQL, Java, PHP, JavaScript, and recently Python. I've never had a problem I could not debug using some careful thought, and well-placed debugging print statements.
I respect that many people say that my techniques are primitive, and using a real debugger in an IDE is much better. Yet from my observation, IDE users don't appear to debug faster or more successfully than I can, using my stone knives and bear skins. I'm sincerely open to learning the right tools, I've just never been shown a compelling advantage to using visual debuggers.
Moreover, I have never read a tutorial or book that showed how to debug effectively using an IDE, beyond the basics of how to set breakpoints and display the contents of variables.
What am I missing? What makes IDE debugging tools so much more effective than thoughtful use of diagnostic print statements?
Can you suggest resources (tutorials, books, screencasts) that show the finer techniques of IDE debugging?
Sweet answers! Thanks much to everyone for taking the time. Very illuminating. I voted up many, and voted none down.
Some notable points:
Debuggers can help me do ad hoc inspection or alteration of variables, code, or any other aspect of the runtime environment, whereas manual debugging requires me to stop, edit, and re-execute the application (possibly requiring recompilation).
Debuggers can attach to a running process or use a crash dump, whereas with manual debugging, "steps to reproduce" a defect are necessary.
Debuggers can display complex data structures, multi-threaded environments, or full runtime stacks easily and in a more readable manner.
Debuggers offer many ways to reduce the time and repetitive work to do almost any debugging tasks.
Visual debuggers and console debuggers are both useful, and have many features in common.
A visual debugger integrated into an IDE also gives you convenient access to smart editing and all the other features of the IDE, in a single integrated development environment (hence the name).

Some examples of some abilities that an IDE debugger will give you over trace messages in code:
View the call stack at any point in time, giving you a context for your current stack frame.
Step into libraries that you are not able to re-compile for the purposes of adding traces (assuming you have access to the debug symbols)
Change variable values while the program is running
Edit and continue - the ability to change code while it is running and immediately see the results of the change
Be able to watch variables, seeing when they change
Be able to skip or repeat sections of code, to see how the code will perform. This allows you to test out theoretical changes before making them.
Examine memory contents in real-time
Alert you when certain exceptions are thrown, even if they are handled by the application.
Conditional breakpointing; stopping the application only in exceptional circumstances to allow you to analyse the stack and variables.
View the thread context in multi-threaded applications, which can be difficult to achieve with tracing (as the traces from different threads will be interleaved in the output).
In summary, print statements are (generally) static and you'll need to re-compile to get additional information if your original statements weren't detailed enough. The IDE removes this static barrier, giving you a dynamic toolkit at your fingertips.
When I first started coding, I couldn't understand what the big deal with debuggers was and I thought I could achieve anything with tracing (granted, that was on unix and the debugger was GDB). But once you learn how to properly use a graphical debugger, you don't want to go back to print statements.

An IDE debugger lets you change the
values of variables at run-time.
An IDE
debugger lets you see the value of
variables you didn't know you wanted
to see when execution began.
An IDE
debugger lets you see the call stack
and examine the state of the
function passed weird values.
(think this function is called from
hundreds of places, you don't know
where these weird values are coming
from)
An IDE debugger lets you
conditionally break execution at any
point in code, based on a condition,
not a line number.
An IDE debugger will let you examine the state of the program in the case of an unhandled exception instead of just crapping out.

Here's one thing that you definitely cannot debug with "print" statement, which is when a customer brings you memory dump and says "your program crashed, can you tell me why?"

Print statements all through your code reduces readability.
Adding and removing them for debug purposes only is time consuming
Debuggers track the call stack making it easy to see where you are
Variables can be modified on the fly
Adhoc commands can be executed during a pause in execution to assist diagnosing
Can be used IN CONJUNCTION with print statements : Debug.Write("...")

I think debugging using print statements is a lost art, and very important for every developer to learn. Once you know how to do that, certain classes of bugs become much easier to debug that way than through an IDE. Programmers who know this technique also have a really good feel of what's useful information to put in a log message (not to mention you'll actually end up reading the log) for non-debugging purposes as well.
That said, you really should know how to use the step-through debugger, since for a different class of bugs it is WAY easier. I'll leave it up to the other excellent answers already posted to explain why :)

Off the top of my head:
Debugging complex objects - Debuggers allow you to step deep into an object's innards. If your object has, say, an array of array of complex objects, print statements will only get you so far.
The ability to step past code - Debuggers will also allow you to skip past code you don't want to execute. True, you could do this manually as well, but it's that much more code you have to inject.

As alternative to debug in IDE you can try great Google Chrome extension PHP Console with php library that allows to:
See errors & exception in Chrome JavaScript console & in notification popups.
Dump any type variable.
Execute PHP code remotely.
Protect access by password.
Group console logs by request.
Jump to error file:line in your text editor.
Copy error/debug data to clipboard (for testers).

I haven't been developing for nearly 20 years, but I find that using a IDE / debugger I can :
see all kinds of things I might not have thought to have included in a print statement
step through code to see if it matches the path I thought it would take
set variables to certain values to make code take certain branches

One reason to use the IDE might be that modern IDEs support more than simple breakpoints. For example, Visual Studio offers the following advanced debugging features:
define conditional breakpoints (break only if a condition is met, or only on the n-th time the statement at the breakpoint is executed)
break on an unhandled exception or whenever a (specific) ecxeption is to be thrown
change variable while debugging
repeating a piece of code by setting the next line to be executed
etc.
Also, when using the debugger, you won't have to remove all your print statements once you have finished debugging.

In my experience, simple printouts have one huge advantage that no one seems to mention.
The problem with an IDE debugger is that everything happens at real time. You halt the program at a certain time, then you step through the steps one at a time and it is impossible to go back if you suddenly want to see what happened before. This is completley at odds with how our brain works. The brain collects information, and gradually forms an oppinion. It might be necessary to iterate the events several times in doing so, but once you have stepped past a certain point, you cannot go back.
In contrast to this, a selected series of printouts/logging gives you a "spatial projection of the temporal events". It gives you a complete story of what happened, and you can go back and fourth several times very easily by just scrolling up and down. It makes it easy to answer questions like "did A occur before B happened". It can make you see patterns you wernt even looking for.
So in my experience. IDE and debuggers are fantastic tools to solve simple problems when something in one single call-stack went wrong, and explore the current state of the machine at a certain crash.
However, when we approach more difficoult problems where gradual changing of state is involved. Where for example one algorithm corrupted a data structure, that in turn caused anohter algorithm to fail. Or if we want to answer questions like "how often do this happen", "do things happen in the order and in the way as I imagine them to happen". etc. Then the "old fashined" logging/printout technique has a clear advantage.
The best things is to use either technique when it is most suitable, for example use logging/printouts to get to some bugs, and pause at a breakpoint where we need to explore the current state more in detail.
There are also hybrid approaches. For example, when you do console.log(object) you get a data-structure widget in the log that you can expand and explore more in detail.This is many times a clear advantage over a "dead" text log.

One thing that I'm surprised I haven't seen in another answer is that the 2 debugging methods are not mutually exclusive.
printf debugging can work quite nicely even if you're using a standard debugger (whether IDE based or not). In particular with a logging framework so you can leave all or most of in the released product to help with diagnosing customer problems.
As noted in pretty much all the other answers here, the key nice thing about a standard debugger is that it allows you to more easily examine (and potentially change) the details of the program state. You don't have to know up front what you might want to look at - it's all available at your fingertips (more or less).

Because debugging multi-threaded applications with print statements will drive you bananas. Yes you can still do it with print statements but you'd need a lot of them and unravelling the sequential print out of statements to emulate the multi-threaded executiong would take a long long time.
Human brains are only single-threaded unfortunately.

Since you asked for pointers to books... As far as Windows debugging goes, John Robbins has several editions of a good book on Windows debugging:
Debugging Applications for Microsoft .NET and Microsoft Windows
Note that the most recent edition (Debugging Microsoft .NET 2.0 Applications) is .NET only, so you might want an older one (like in the first link) if you want native code debugging (it covers both .NET and native).

I personally feel the answer is as simple as "A integrated debugger/IDE gives you a wealth of different information quickly without the need for punching in commands. The information tends to be there in front of you without you haven't tell it what to show you.
The ease in which the information can be retrieved is what makes them better than just command-line debugging, or "printf" debugging.

Advantages of a debugger over a printf (note not an IDE debugger but any debugger)
Can set watchpoints.
This is one of my favourite ways of finding memory corruptions
Can debug a binary that you can't recompile at the moment
Can debug a binary that takes a long time to recompile
Can change variables on the fly
Can call functions on the fly
Doesn't have the problem where debug statemenets are not flushed and hence timing issue can not be debugged acuratly
Debuggers help with core dumps, print statements dont'

This is what I use most on VS.NET debugging windows:
Call stack, which is also a great way to figure out someone else's code
Locals & Watches.
Immediate window, which is basically a C# console and also lets me change variable contents, initialize stuff etc.
The ability to skip a line, set the next statement to be executed somewhere else.
The ability to hover over variables and have a tool-tip showing me their values.
In summary, it gives me a 360 degree view of the state of my executing code, not just a small window.
Never found a book teaching this kind of stuff, but then again, it seems to be quite simple, it's pretty much WYSIWYG.

A debugger can attach to a running process
Often easier to debug threaded code from a debugger

With an IDE debugger you can see the values of ALL the variables in the current scope (all the way up the call stack) whenever you halt execution.
Print statements can be great but dumping so much information to the screen at any given place can produce a whole lot of print statements.
Also, many IDE debuggers let you type in and evaluate methods, and evaluate members while you are halted, which further increases the amount of print statements you'd have to do.
I do feel that debuggers are better for some languages than for others however...
My general opinion is that IDE debuggers are absolutely, amazingly wonderful for managed languages like Java or C#, are fairly useful for C++, and are not very useful for scripting languages like Python (but it could be that I just haven't tried a good debugger for any scripting languages yet).
I absolutely love the debugger in IntelliJ IDEA when I do Java development. I just use print statements when I use Python.

As someone said above: Debugger != IDE.
gdb and (back in the day) TurboDebugger (stand-alone) work just fine for the languages they support[ed], thank you. (or an even older technology: Clipper debugger linked into the xBase executable itself) -- none of these required an IDE
Also, though C/++ coding is more rare, printf statements sometimes mask off the very bug you are trying to find! (initialization problems in auto vars on the stack, for instance, or memory allocation/alignment)
Finally, as others stated, you can use both. Some real-time-ish problems almost require a print, or at least a judicious "*video_dbg = ( is_good ? '+' : '-');" somewhere into video memory. My age is showing, this was under DOS :-)
TMTOWTDI

In addition to much of what the other posters have said, I really like stepping through one line at a time along with the computer, as it forces me to think about one line at a time. Often I will catch the bug without even looking at variable values simply because I am forced to look at it as I click the 'next line' button. However, I don't think my answer will help you, Bill, because you probably have this skill already.
As far as learning resources go, I haven't used any -- I just explore all the menus and options.

Is this even real question from real programmer?
Anyone who spent even 5 mins debugging with print statements and debugging with IDE - it will OCCUR to him/her without even asking!

I've used both prints and IDEs for debugging and I would much rather debug using an IDE. The only time for me when that doesn't work is in time critical situations (like debugging online games) where you litter the code with print statements and then look at the log files after it has gone horribly wrong. Then if you still cannot figure it out, add more prints and repeat.

Just wanted to mention a useful feature of a console debugger vs printf and vs debugger in an IDE.
You can attach to a remote application (obvioustly, compiled in DEBUG mode) and inspect its state dumping the debugger output to a file using POSIX tee utility. Compared to printf, you can choose where to output the state in run-time.
It helped me a lot when I was debugging Adobe Flash applications deployed in an agressive environment. You just need to define some actions that print required state in each breakpoint, start the console debugger with fdb | tee output.log, and walk through some breakpoints. After that you can print the log and analyse the information by thorough comparison of the state in different breakpoints.
Unfortunatelly, this feature [logging to a file] is rarely available in GUI debuggers, making developers compare the state of objects in their head.
By the way, my opinion is that one should plan where and what to debug before staring a debugger.

Well another thing is that if you join a new old project and nobody really knows how the code is doing what it's doing, then you can't debug by echoing variables/objects/... b/c you have no idea what code is executed at all.
At my job I am facing exactly that kind of situation and visual XDebuging helps me getting an idea about what is going on and where, at all.
Best regards
Raffael

In addition to the many things that have been already mentioned, one of the most important advantages of a debugger over printf is that using printf statements assumes that you know in which function the bug resides. In many cases you don't, so you have to make a few guesses and add print statements to many other functions in order to localise it. The bug may be in framework code or somewhere far removed from where you think it is. In a debugger it is far easier to set breakpoints to examine the state in different areas of the code and at different points in time.
Also, a decent debugger will let you do printf-style debugging by attaching conditions and actions to breakpoints, so that you still retain the benefits of printf debugging, but without modifying the code.

Debugging in an IDE is invaluable in an environment where error logs and shell access are unavailable, such as a shared host. In that case, an IDE with a remote debugger is the only tool which allows you to do simple things such as view stderr or stdout.

A problem with using print statements is it makes a mess of your code. IE, you have a function with 10 parts to it and you know it crashes somewhere, but you're not sure where. So you add in 10 extra print statements to pinpoint where the bug is. Once you've found and solved your bug, you now have to clean up by removing all of those print statements. Maybe you'll do that. Maybe you'll forget and it'll end up in production and your user's console will be full of debug prints.

Wauw, do I like this question. I never dared to pose it...
It seems that people just have different ways of working.
For me what works best is:
Having a solid mind model of my code, including memory management
Using instrumentation (like print statements) to follow what's happening.
I've earned my living programming for over 40 years now, working at non-trivial technical and scientific applications in C++ and Python daily, and I have the personal experience that a debugger doesn't help me a bit.
I don't say that's good. I don't say that's bad. I just want to share it.

It's not just debugging. An IDE helps you build better software faster in a lot of ways:
refactoring tools
intellisense to make api's more discoverable, or remind of exact spelling/case of familiar items(not much use if you've used the same system for 15 years, but that's rare)
save on typing by autocompleting variable and class names
find certain kinds of errors before you even start to compile
Automatically jump to variable/method/class declarations/definitions, even if they're not in the same file or folder.
Break on unhandled and handled exceptions
I could go on.

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