c++

Access reading error when using class member variable

Hi, I have a class with private member variables declared in a header file. In my constructor, I pass in some filenames and create other objects using those names. This works fine. When I try to add another member variable, however, and initialize it in the constructor, I get an access reading violation. I sent the code to someone else ...

Why isn't strlen working for me?

char p[4]={'h','g','y'}; cout<<strlen(p); This code prints 3. char p[3]={'h','g','y'}; cout<<strlen(p); This prints 8. char p[]={'h','g','y'}; cout<<strlen(p); This again prints 8. Please help me as I can't figure out why three different values are printed by changing the size of the array. ...

Interpreters: Handling includes/imports

I've built an interpreter in C++ and everything works fine so far, but now I'm getting stuck with the design of the import/include/however you want to call it function. I thought about the following: Handling includes in the tokenizing process: When there is an include found in the code, the tokenizing function is recursively called w...

How to use linked resource with eclipse CDT ?

I found it very difficult to configure linked resource in Eclipse CDT. Folder "wspolne" is located somewhere in the system, I'd like to use .cpp .h files from it in my current project, but avoid copying it. From what I read about Linked Resources is a solution, but I can't build a projct :/ I followed instuctions described here with ...

Basic Custom String Class for C++

EDIT: I don't want to delete the post because I have learned a lot very quickly from it and it might do someone else good, but there is no need for anyone else to spend time answering or viewing this question. The problems were in my programming fundamentals, and that is something that just can't be fixed in a quick response. To all w...

No network packets sent immediately after quick physical disconnect and reconnect.

I am using Boost's ASIO libraries to establish a UDP connection to a remote server. To make sure the connection is active, every second a keep-alive message is sent to the server. I have noticed that if I unplug the network cable and reinsert it quickly, the first 2 or 3 keep-alive messages after the reinsert are never sent. I tested t...

Use-cases of pure virtual functions with body?

I recently came to know that in C++ pure virtual functions can optionally have a body. What are the real-world use cases for such functions? ...

Any difference in compiler behavior for each of these snippets?

Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } Wha...

C++ argv path specifier

In the interpreter for my programming languages I have to correctly handle the parts in case the import function is called. I then need to check if such a file is in the /libs folder (located at the same place as my executeable!) and if it doesn't exist I have to check in the directory of the current script. How can I get the exact pat...

Is there an equivalent to BCEL (Java .class manipulation) but in C or C++

Is there a C or C++ compatible library for reading and writing Java class files? I.e. something like Apache BCEL. ...

C++ and Dependency Injection in unit testing

Suppose I have a C++ class like so: class A { public: A() { } void SetNewB( const B& _b ) { m_B = _b; } private: B m_B; } In order to unit test something like this, I would have to break A's dependency on B. Since class A holds onto an actual object and not a pointer, I would have to ...

Why does C++ allow variable length arrays that aren't dynamically allocated?

I'm relatively new to C++, and from the beginning it's been drilled into me that you can't do something like int x; cin >> x; int array[x]; Instead, you must use dynamic memory. However, I recently discovered that the above will compile (though I get a -pedantic warning saying it's forbidden by ISO C++). I know that it's obviously a b...

Cannot change the height of a combo box in the VS Dialog Editor

Any combo box I create seems to be stuck at 12 dialog units in height. Microsoft's guidelines for spacing and sizing of controls in dialog boxes state that a combo box should be 14 dialog units high. I have even tried editing the resource file in notepad and recompiling in Visual Studio without opening the resource editor - but the com...

small & readable scheme interpreter in C++ ?

Anyone know of a good / small scheme interpreter in C++? Perferably something < 2000 LOC, with a simple garbage collectro (either compacting or mark & sweep), no need to support all of R5RS, just basics of if/lambda/set!/cons/car/cdr and some basic operations. Thanks! ...

Problem Making C++ script

Hello all, I am not sure if I can post this sort of question (apologies in advance) but I am trying to build something from this blog post. # mkdir wkthumb # cat > wkthumb.cpp # qmake -project # qmake && make # ./wkthumb I have no experience with this, but I download all the files needed in the directory wkthumb using git. I have go...

Convert templated parameter type to string

I've got a small bit of DRY going on in code I and others have written that I'd like to reduce but I'm failing to figure out how to get it done. This is legacy COM code but it's interfering with the readability. I'd like to do the following: bool queryInterface<class T, class V>(T &_input, V &_output, Logger &_logger){ if( FAILED(...

Make Errors: Missing Includes in C++ Script?

Hello all, I just got help in how to compile this script a few mintues ago on SO but I have managed to get errors. I am only a beginner in C++ and have no idea what the below erros means or how to fix it. This is the script in question. I have read the comments from some users suggesting they changed the #include parts but it seems to ...

How can a Windows program temporarily change its time zone?

I've written a function to return the time_t value corresponding to midnight on a given day. When there is no midnight for a given day, it returns the earliest time available; that situation can occur, for example, when Egypt enters daylight-saving time. This year, the time change takes effect at midnight on the night of April 29, so the...

Combine two numbers into one. Example: 123 and 456 become 123456

In C++, how do I combine (note: not add) two integers into one big integer? For example: int1 = 123; int2 = 456; Is there a function to take the two numbers and turn intCombined into 123456? EDIT: My bad for not explaining clearly. If int2 is 0, then the answer should be 123, not 1230. In actuality though, int1 (the number on the...

Is "for(;;)" faster than "while (TRUE)"? If not, why do people use it?

for (;;) { //Something to be done repeatedly } I have seen this sort of thing used a lot, but I think it is rather strange... Wouldn't it be much clearer to say while (TRUE), or something along those lines? I'm guessing that (as is the reason for many-a-programmer to resort to cryptic code) this is a tiny margin faster? Why, and ...