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Closed 10 years ago.
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How to avoid entering library's source files while debugging in Qt Creator with gdb?
anybody know how to tell gdb to only enter code that is in your project? I know it's hard for a debugger to know what is "in the project" and what is a library....but I thought some naive checks could help, eg don't look in any files that aren't in the users home directory. I frequently have code like this:
MyFunction(complexVarable, complexvar); //passed by value
and gdb insists on going through the copy constructors of the two passed values, but all I care about is MyFunction. Any tips? There are two parts to the question,
ignore code that isn't mine (not in home dir)
skip copies for function calls.
thanks.
EDIT: btw I use emacs, maybe there are some tools there I missed, but I'm open to using external gdb frontends.
As per my opinion this cannot be done.
every project has a flow of data from one function to other.
gdb is designed to work on the flow of data.
so if your project is somewhere in the middle of the flow,gdb cant help you,since evry function has some purpose to do with the input it gets and output it gives.
all you can do is create the same function separately and replicate the scenario as if its running in teh flow by giving the inputs it needs and output it gives.
Related
This question already has answers here:
Is it possible to "decompile" a Windows .exe? Or at least view the Assembly?
(16 answers)
Is there a C++ decompiler? [closed]
(5 answers)
Closed 4 years ago.
I lost the source code to an executable file but still have the actual file. Is there any way to retrieve the original C++ code?
Duplicate of this question here.
Yes, it is possible, however when it comes to peeking function bodies and the like, you might have a little less luck. Operating systems like Kali Linux specialize in de-compilation and reverse engineering, so maybe look into a VM of that. And of course, windows has a lot of applications you can use as well to check the application code.
Look over the other question for specific app suggestions. :)
Edit : You will most likely have lost all your logic and function bodies, but you might be able to recover the overall structure. It's your EXE so you might be more familiar with how it was all connected up.
You cannot get the original source code but you can decompile the binary into source code using tools given in this similar question: Is there a C++ decompiler?
The output source code will not look like the original as the compiler will have optimised the original source when generating the executable.
Short answer NO.
Long answer, because C++ doesn't use some intermediate code like C# or Java you cannot decompile the app in some readable format. But if you can read assembly maybe you can save some time.
Here's some background of what I'm trying to achieve.
I'm in need of parsing C++ source code to find all instances where function X is called. This seems doable in libclang as mentioned in this post: Find all references of specific function declaration in libclang (Python) (though the answer implies it isn't as simple as you might think).
However, problem with libclang is that using it on Windows is often not recommended by many people. I can't use it on Linux because I'm hoping to use it on existing Visual C++ code that uses winapi.
With this barrier, I asked a colleague and he suggest I just simply search the source code using regular expression. I have my doubts that this is easy.
Can someone tell me if this approach is recommended?
Edit to address the comment of what my goal is: I need to do it programmatically because I'm tryng to integrate it to an infastructure that checks where the code was editted and then gives you an output on which end-user functionality is affected by that edit and thus needs to be rechecked. If I were to do this manually via the "find references" options in IDE, this means "finding references" in multiple levels until I reach the end-user level which is a lot of work for large code and prone to error.
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Convert assembly to machine code in C++
(3 answers)
Closed 6 years ago.
I would like to include NASM itself (the assembler) in a C++ project. Can I compile NASM as a shared library? If not, is there another assembler that works as a C or C++ library?
I checked libyasm but couldn't understand how I can use it to assemble my code.
Woah, this exploded when I was away.
I had solved this problem by tampering with the YASM source code, and totally forgot about the question in SO as it received absolutely no attention 8 months ago. Below are the details, followed by a better suggestion.
For the project that I had in mind, I needed to use YASM as a library, and I was in a hurry because I was doing this for a company. Back then there were no good libraries that I was aware of; and I had concluded that getting used to the LLVM framework was an overkill for the task (because all I wanted was to assemble singular x86 - x86_64 instructions and receive the bytes).
So I downloaded the source code for YASM.
Upon meddling with the code for a while, I noticed that the executable receives the file paths for input and output files; and passes these two strings along. I wanted char arrays in memory for the input and output; not files. So I figured, maybe if I could find all FILE pointers that are passed around, I can convert them to char pointers, and change every file read/write to array operations.
This turned out to be even more cumbersome than it sounds. Apparently YASM does not open input/output files once and uses the same FILE pointers; instead it passes around copies of the filepath strings. I needed a script that could make all the necessary changes for me, this wasn't good for me.
Eventually, I found all fopen/fclose calls in the program with a script, and replaced them with my_fopen/my_fclose. For each file that I made these replacements, I included my header file in which I implemented these two functions.
In both of these functions, I checked the incoming string, compared it with "fake_file". If they are equal, I passed a 'fake' FILE pointer pointing to two portions of memory, obtained from the function calls fmemopen and open_memstream. Otherwise I simply called the actual fopen/fclose functions. In other words, I redirected these two calls (only for a given filename) to a memory file. Then, I called the library with the filename parameter set to 'fake_file'.
Since I have had limited myself to Linux at that point, this approach worked for me. I also found out (using Valgrind) that there was a memory leak in the library version, so I wrote a very primitive garbage collector for it. Basically I wrapped malloc's etc. to keep track of all allocations that are not freed, and clean them after each execution.
This approach also allowed me to automate these changes using a script. Unfortunately I did all these in a company so I cannot leak any actual code.
Better suggestion:
As of May 31, 2016; you can use Keystone Engine instead. It is "based on LLVM, but it goes much further with a lot more to offer." The disassembly engine Capstone and this are a near perfect couple for assembly and disassembly. If you need either of these components, I suggest these instead of doing the hacks I described. Both of these engines are currently being developed; and even though Keystone has some small bugs, Capstone is very robust at the moment.
TL;DR: Use keystone.
I had a question about debugging in Visual Studio (2010 if it actually matters). Sometimes I am running an application and I want to break out of it to debug or to see where it has hung, etc. However, I find that very very often the "break-out point" seems to be in some random .c file in the standard library. I understand why this is (its executing some method somewhere), but I want to know where the last point it was in the code I have written is. Is there a way to do this?
If I try and "step", the debugger seems to always return something like "there is no code to debug for the current location" or something, which I am guess means that it is making its way through some machine code. Again, that's fine, but I want to know what the last executed call in my main.cpp file was; is there a way to get this information? The call stack doesn't seem to help either, it always has a list of non-sensicle calls and even if I can locate the latest point in the call stack that is from my main.cpp, it doesn't seem to provide any useful information (like a line number or a function name... I
think it's showing the mangled name).
What do most people do in this situation? I apologize, I know I'm a beginner, and I'm sorry I don't have a concrete example, but I feel I see this often at work.
Any help appreciated, thanks!
K
Once you've paused the program observe the call stack (Debug->Windows->Call Stack) at that point, find where the last layer of your code is and get there by clicking on the corresponding line in the call stack window.
The "Step Out" command, Shift+F11, will finish execution of the current function and break immediately after the return.
You can use Step Out a few times to step out of the system calls back to your code.
The "Step Into Just My Code" option sounds like it may do what you want, but I've never used it.
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Closed 12 years ago.
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Have you used any of the C++ interpreters (not compilers)?
Hi,
I am currently learning C++ and a beginner in programming in general. I've been trying to write some code to a few programming problems from the book I'm using. What I find is that often I make mistakes in what I write and those mistakes come up when the program is run. Its usually quite obvious where in the program I've gone wrong when there is regular output. But in a long computation I'm often not sure why a particular code has acted a certain way. I've also looked at Python recently. Python works with an interpreter, which can take any piece of Python code and compute its output.
I was wondering if there was something similar for C++. Right now when I want to check a line or block of code I have to comment out a lot, save it, compile it, and then run it from a command line. And I have to do that many times for a single error until I've solved it. Is there a way to type code into an active terminal which would run code and show me output? What would be better still would be a way to select a block of code (like you select text) or multiple blocks (to see how a function is being handled) within the IDE and click run to run just that block of code and see its output without having comment out irrelevant lines or to save the file. The compiled code could just reside in memory.
CINT is a c & C++ interpretter that accepts nearly all valid C++. Unfortunately many Linux distros do not offer it, and you'll probably have to build it from source... and that is a non-trivial task.
Typically a debugger is used to step through code line by line, starting at a chosen breakpoint, and keep watch of all variables/values.
Unit testing is a technique to test smaller pieces of code.
A stepping debugger, as found in most IDEs will help you with this.
Here (for example) is a description of how to set the Execution point in In Visual Studio, which sounds like what you want to do.
For certain situations, the "Immediate Window" may be of use to you. It allows you to type in expressions to evaluate immediately.
Rather than just running individual lines independently, or relying on print statements to tell you the state of whatever variables you have decided to print, you can use the debugger to run to the point of interest (where you will have set a breakpoint), then you can examine the state of any in-scope variables, or even alter the normal flow of the program.
There are some solutions that try to do this - the ones I know are Ch and TextTransformer.
However, I doubt that this works very well. C++ is not at all designed to run as an interpreted language.
One of the problems is that C++ is very, very hard to parse. And this makes it very hard to provide certain types of tools that are usual for other languages. For example, I don't think there is any C++ refactoring tool that really works well.
C++ is a compiled language not like python. But there are few c/c++ interpreters out there but not sure about their features. Check these out: Ch interpreter and CINT
If you really want to learn c++ please do not use the c/c++ interpreters.
If you insist on using a interactive interpreter there is since a long time CINT which is the default interpreter used in the ROOT project. It got better over the years, but still has only limited capabilities when dealing with templates. Also, there is a move to replace it with a JIT compiling interpreter based on clang inside the ROOT project.
If I were you I would learn how to run compiler and an interactive debugger like suggested in some comments already.