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Closed 11 years ago.
I have a really nasty bug in my program, which grew quite complex over time. It's probably the worst bug I've ever had.
I think that it might be related to a static variable initialization fiasco, but how can I ensure myself of that?
When the bug strikes, the program crashes due to heap corruption at a random point after startup, but far inside the main() function.
To be honest, I don't know what to do.
I'm on Windows 7 using Microsoft Visual Studio 2010
my program, which grew quite complex
over time
Do you keep backups of previous versions?
Find an older version that worked and continue working based on that version...
There is a famous quote out there:
"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." --Brian Kernighan
If this program has become more complicated than you can handle then it may be time to think about refactoring.
(This is in no way intended to be demeaning or to be taken as a personal attack...)
Run your program in the debugger, and step through the code until you see what's wrong. Place breakpoints liberally anywhere you think the bug might be caused.
Try debugging your program with gdb.
Related
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Closed 9 years ago.
Ok so I wrote this minimal C code and complied it to an executable in release mode
1.void main()
2.{ for(;;); } //this is here to make the app hang.
The executable file size itself is 6kb, I didn't include any headers. Even if the entire exe file gets copied to the ram, apparently it shouldn't occupy more than 7 kb, nevertheless the OS allocates 320 kb, why is that? I'm using windows.
It seems like you're confused and mixing a wide variety of concepts. Let me try to explain:
That program is very clearly an infinite loop which explains why it doesn't end (or what you call "hang").
The compiler/linker still need to write a valid executable for your OS, and this involves a bunch of headers and stuff, which could be easily consuming 6kb.
320kb in a mainstream OS at this point in time seems like almost nothing and it can mainly be OS overhead. It is hard to say more without knowing what OS.
I strongly encourage you to disassemble your code. Another option is to play with your compiler options to optimize for executable size. I think the bottom line is that you're expecting that since your program doesn't do anything useful its size should be zero, and this is an unreasonable expectation.
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Closed 10 years ago.
I'm looking at the possibility of building a system where when a query hits the server, we turn the query into c++ code, compile it as shared object and the run the code.
The time for compilation itself needs to be small for it to be worthwhile. My code can generate the corresponding c++ code but if I have to write it out on disk and then invoke gcc to get a .so file and then run it, it does not seem to be worth it.
Are there ways in which I can get a small snippet of code to compile and be ready as a share object fast (can have a significant start up time before the queries arrive). If such a tool has a permissive license thats a further plus.
Edit: I have a very restrictive query language that the users can use so the security threat is not relevant. My own code translates the query into c++ code. The answer mentioning clang is perfect.
Running Clang in JIT mode should provide the speed you need, and example can be found here, safety on the other hand is something else...
Ch also had a JIT added, and seeing as its an interpreter, it might provided an easier sandboxed/controlled environment.
In addition to Necrolis answer, there's also specialized C++ parser Cling. Might come in handy.
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Closed 10 years ago.
I am writing a code in c++. Compared to my friends the compiling time high. what could be the reason for this? Its taking around 4 seconds. But for my friends its getting compiled immediately.
This is an impossible question there are so many factors, but some thing to look out for:
heavy use of template meta programming - are you using something like boost spirit
are the header file including other header when it could be a forwatd declaration
are there uneeded headers.
Is there just a lot of code
Is your build system correct? Is it recompiling code that hasn't changed. Look at make file if you haven't already.
Is their system better than yours.
Finally I would love my code to compile in 4 seconds.
Do you have optimizations turned on? That will slow things down.
Do you have a Temp directory mapped to a network drive? That will slow things down.
Are you linking from a network drive? That will slow things down.
Talk about an open ended question, but here are some quick reasons;
Slow computer (CPU/Disk etc)
Too little memory.
Different compiler (they vary greatly in speed).
Precompiled headers vs. non precompiled headers.
Different options (RTTI/optimization/...)
Esp. in Visual Studio, plugins slowing your IDE down.
Code structure (are you including un-necessary headers)
Compiling everything every time vs. using Makefiles or a smart IDE.
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Closed 11 years ago.
It seems like the bugs in my project are evolving. While in the beginning time, causers of program crashes were easily to spot using the debugger (the line it points to after the program crashes), it's different now.
Many bugs cause the program to crash in completely arbitary places not even closely related to them.
How can I spot bugs "hiding" from the debugger in a better way?
(I use Visual Studio 2010)
Profile your code for memory corruption, memory overwrites and memory leaks.
Root cause analysis.
When you find an obvious bug, don't just fix the bug, fix the coding style that allowed it.
If you have any code using raw memory and pointers, replace it by memory allocated using std::vector and its iterators. It will compile to exactly the same speedy code in Release mode, but in Debug mode it will used checked iterators, which will catch some bugs as early as possible.
Use memory corruption checking utilities, like gflags or debug heap. "Floating" crushes almost always come from corrupted memory in C++ programs
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Closed 12 years ago.
This is a further question for my previous one here.
Is there a general solution for this?
Fix all dangling pointers
Fix all buffer overflows
Use pointers only where they are really needed
Reading your original post I'm not 100% you are facing a heap-corruption and you really hope you don't because if you would this is one of the most tricky errors to track down and AFAIK there are no solutions that always work.
However, if you are positive its a heap-corruption and you are on the windows platform you could try out the tool gflags. This advanced debugging tools allow you to install a debug heap manager in order to make it possible to find certain kinds of heap corruptions. One of the neat options it has is to make each allocation in it's own page or to write protect the heap datastructures. This makes it easier to pinpoint the exact location of the heap-corruption. It sucks lots of memory and CPU though.
Another tip if you are using Visual Studio is that if you manage to find that something is corrupting the data after a certain point of time and you wish to find the code that corrupts the data you can use Data Breakpoint to break whenever someone changes the data in question.
I wish you good luck.
Adding to swegi's answer I would check all your C++ constructors and all C initializations. Transform all dynamic C++ constructors (those where you put the init code in the function body) into static ones (where you initialize with the special constructor syntax). And be sure that you init all pointers and pointer members to 0. For C, I would initialize all variables.
Then, on unix I would use valgrind, usually this is quite good in finding all access violations and if you compile with all debugging options on it is able to trace it to the source line. There should be something similar on windows, too.