hooah posted:

I'm just now running across char* objects, and am somewhat confused. The book says they're pointers, but unlike (all?) other pointers, you can assign a string directly to the pointer, rather than to the dereferenced object. Are char* objects different just because, or is there an explanation for this difference?

Spatial posted:

It's because string literals aren't objects, they're pointers to null-terminated arrays of char primitives.

FamDav posted:

While you can't pass arrays by value (or even have an array be an argument without it auto-decaying to a pointer), you can use pointers/references to fixed size arrays and get some sweet type checking.

code:

void f( char (&x)[3] ) {}

int main()
{
	char x[2];
	char y[3];
	//f(x); // ERROR, incompatible type
	f(y);
}

FamDav posted:

what signifies an object?

tractor fanatic posted:

C++ code:

class base{
public:
    virtual int a_thing() = 0;

    int use_a_thing(){
        return a_thing() * 2;
    }
};

class der : public base{
    int count;
public:
    virtual int a_thing(){
        return count++;
    }
};

int main(){
    der d;
    d.use_a_thing();
}

If I were to call der::use_a_thing() in a tight inner loop, where the full definition would be visible to the compiler, would I need to worry about the virtual? Would the compiler (specifically MSVC) be able to inline the whole thing?

tractor fanatic posted:

If I were to call der::use_a_thing() in a tight inner loop, where the full definition would be visible to the compiler, would I need to worry about the virtual? Would the compiler (specifically MSVC) be able to inline the whole thing?

slovach posted:

I expected 0x00F800F8... how did it end up like that?

OctaviusBeaver posted:

I have a really basic conceptual question.

In this snippet:

code:

    int testing[3];
    testing[1] = 11;
    int *ptr;
    ptr = &testing[0];
    printf("%d\n",*(ptr+1)); //outputs 5
    printf("%d\n",*(ptr+sizeof(int)));

why does the (ptr + sizeof(int)) printf spit out garbage while the printf for (ptr+1) doesn't? Since I have an array of integers, which on my machine are size 4, shouldn't I have to skip ahead 4 memory addresses to reach the second element of the array? Why does that fail while my (ptr+1) skipping ahead 1 memory address works?

That Turkey Story posted:

The integer that you add to a pointer is always implicitly in units equal to the size of the pointed-to type. In other words, adding 1 to the pointer in your example moves by sizeof(int) bytes. Adding sizeof(int) increments by sizeof(int) * sizeof(int) bytes.

Paul MaudDib posted:

I basically have some code that iterates data, and several different simple payload functions that I want executed on them. I don't want to switch operations midstream, and I also don't want the overhead of making a function call. I basically just want to stick each payload into the function, compile it in turn, and give it a defined name, but without having the redundancy of the same iteration code being everywhere if I just copied and pasted five times.

So basically I want:

code:

void iterate_function(int * data, inline int func(int), int n);

inline int payload_a(int);

void deploy_payload_a(int * data, int n)
{
  iterate_function(data, payload_a, n);
}

How can I make that happen?

e: Perhaps prototype the payload and iteration functions, and then #define the deploy function? Would that inline it properly?

tractor fanatic posted:

C++ code:

class some_type;

struct a_pair{
    some_type a, b;
};

a_pair array_of_pairs[16];

some_type * p = &array_of_pairs[0].a;

In practice, can I walk through all of the some_type in the array_of_pairs by iterating p, regardless of whether some_type is packed by compiler attributes? a_pair is not packed.

edit: probably not since an array of some_type would be unaligned so iterating a some_type* wouldn't work.

tractor fanatic posted:

C++ code:

class some_type;

struct a_pair{
    some_type a, b;
};

a_pair array_of_pairs[16];

some_type * p = &array_of_pairs[0].a;

In practice, can I walk through all of the some_type in the array_of_pairs by iterating p, regardless of whether some_type is packed by compiler attributes? a_pair is not packed.

Jerry SanDisky posted:

Is there a reason you can't just call a common error logging function?

Dren posted:

This might get sent me straight to the coding horrors thread but does goto'ing out of an exception block to some common error logging then rethrowing work?

rjmccall posted:

No. Operand-less throw rethrows the (latest) exception currently being handled. If you leave the catch handler for an exception without rethrowing it, the exception is no longer being handled and is destroyed.

Jerry SanDisky posted:

Unrelated to the above question, but I was under the impression that you can have an exception live past the catch by getting an exception_ptr to it via std::current_exception. Is that the case?

rjmccall posted:

No. Operand-less throw rethrows the (latest) exception currently being handled. If you leave the catch handler for an exception without rethrowing it, the exception is no longer being handled and is destroyed.

Doctor w-rw-rw- posted:

Diving into C++ since I figure it's about drat time I finally learn it. Is CMake an okay build system?

More generally, any tips for how to write and run code effectively? I'm thinking of using Vim with YouCompleteMe (which is a module that uses LLVM to do completions), but I have no beef with Eclipse. I'm on a mac, so Visual Studio is out.

Doctor w-rw-rw- posted:

Diving into C++ since I figure it's about drat time I finally learn it. Is CMake an okay build system?

More generally, any tips for how to write and run code effectively? I'm thinking of using Vim with YouCompleteMe (which is a module that uses LLVM to do completions), but I have no beef with Eclipse. I'm on a mac, so Visual Studio is out.

Hughlander posted:

evensevenone posted:

Doctor w-rw-rw- posted:

So about the language itself - assuming familiarity with most languages, what are the things fairly unique or uncommon in C++ that I should read up on?

Suspicious Dish posted:

That Turkey Story posted: