#include <iostream> using namespace std; int main() { bool test; cout << test << endl; return 0; } I cannot stop at bool test; No matter how many optimizations I disable... it seems as if it gets removed or something.

#include <iostream> using namespace std; int main() { bool test; do { test = true; } while(test); return 0; } Also, I've tested here where the variable gets used. But inside another scope... So... when does the variable get created??

So, there are multiple answers for that. By the standard it's created in the outer scope and destroyed at the end of that scope. But the compiler can do optimizations to your code while these optimizations don't change observable behavior of the app (this doesn't count any UB, so be careful with that). So in fact the value may not exist at all. Also infinity loop without an exit condition is UB, so there are no guarantees about that, so the compiler is free to generate anything from this code or even not generate anything for it at all

Don't mind the infinity loop. It's just an example I made up for testing. So the compiler creates the variable just right before the it gets it's value? Inside the scope?

It depends, it can be that it becomes the part of the code instruction and memory for it is not allocated on the stack at all. You can use godbolt.org to investigate the assembly generated for your code for debug and release versions

I wish I knew assembly. Compilers are really confusing... XD

If you just want to debug your code, you need to disable optimizations (depends how you compile it, sometimes it's as easy as set "debug" instead of "release" in your IDE)

I was really confused because I thought it was supposed to stop there. I guess that's not always true. But what's interesting is that the optimizations are not done to strings (I suppose). I can declare a string variable and not initialize it. And gdb can stop there.

If you think you know all the ways to shoot yourself in the foot in C++ - you could be wrong. Let's embark upon an exciting journey along the perilous paths of our favourite programming language. We'll see hidden traps, navigate around UB-filled pits, and see how cruel the Standard can be. https://youtu.be/zu1bk340jgo

Thanks. I'm using makefiles and set the optimization flag to -O0. I somehow understood it better with a few experimentation. I guess gdb cannot detect that line of code because the compiler optimized it. Thus being unable to set breakpoint there.

@roxifas this is an ad right

Strings are more difficult to optimize, especially if you set the value for them, because it requires memory allocation on heap

Strings are more difficult to optimize, especially if you set the value for them, because it requires memory allocation on heap

I was trying to accept names in cpp and save it to a file in binary and then display it . But everytime the display comes the first letters of each names are cut off, can anyone help me with this. I wanted to forward the code but its too long here

separate being in your university and practice

Anyone? it's kind of urgent please

try setting your buffer to all nulls, before you write your name

yes.. when you go to memcpy(buf, name, size); or strcpy(buf, name, size); for (int i = 0; i < SIZEOFBUF; i++) buf[i] = 0; THEN copy your name to it

where is name defined

system("cls"); int r,flag; ofstream fout("Record.txt",ios::app); cout<<"\n Enter Customer Details"; cout<<"\n **********************"; cout<<"\n\n Room no: "; cin>>r; flag=check(r); if(flag) cout<<"\n Sorry..!!!Room is already booked"; else { room_no=r; cout<<" Name: "; gets(name); cin.ignore(); cout<<" Address: "; gets(address); cin.ignore(); cout<<" Phone No: "; gets(phone); cin.ignore(); fout<<room_no<<"\t"<<name<<"\t"<<address<<"\t"<<phone<<endl; cout<<"\n Room is booked!!!"; } cout<<"\n Press any key to continue!!"; getch(); fout.close();

i cant help you without seeing how its defined

-D is an optimization flag? Or preprocessor flag? I can't understand.

Wait, I've read the docs incorrectly, nevermind this, and I've read description of -O0 wrongly as well

#include <iostream> const int nmax = 100001; bool isPrime[nmax]; int listPrime(int num){ for(int i = 2; i<=num;i++){ isPrime[i] = true; } for(int i = 2; i<=num/2;i++){ if(isPrime[i]==true){ for(int j =i*2;j<=num;j+=i){ isPrime[j] = false; } } } for(int i=2;i<=20;i++){ if(isPrime[i] == true){ return i; } } } int main (){ //Qn: Call the above function and get return all prime number lists from 1-100 // but dont touch listPrime Function untill you think you can not do it return 0; }

any suggestions?

why not C Primer Plus by Stephen Prata?

#res

what to read there... lot of messages there

Read the first two messages there

which book would u suggest for learning c++

Did you read the messages that I suggested earlier?

yes

there are options thats why im asking

For Beginners, you can choose either one of the two books mentioned. Both are good. For intermediate and advanced, read all the books in the order specified

and any lecture source.. u can suggest?

and any lecture source.. u can suggest?

Hello, please what are the softwares I'll need if I want to start practicing c/c++ What will I use to run it and how do I set it up?

What OS do you use?

Windows 10 Pro

You can download Visual Studio Community Edition (not Visual Studio Code, that's a different thing), find some tutorials how to use it, and set it up with C++ components. This should be enough to start. Tutorials are important because it's not user-friendly at the beginning, difficult to find where is what.

I'm using a getline function in my program when execution reaches it, it doesn't waot gor user input it just continues.

I'm using a getline function in my program when execution reaches it, it doesn't waot gor user input it just continues.

I'm using a getline function in my program when execution reaches it, it doesn't waot gor user input it just continues.

did you include string header file?