In another forum, this example code fragment was stated as being an example of undefined behavior. My understanding is that a literal string exists from program start to program termination, so I don't see the issue, even though the literal string is probably in a different part of memory.
Code: /* ... */
const char *pstr = "example";
/* or even */
char *pstr = "example";
/* as long as no attempt is made to modify the data pointed to by pstr, */
/* unless pstr is later changed to point to a stack or heap based string */
how string literal that works with the cin object?
char * str = "This is a string constant";
Is the str stored the address of the first character of the string literal?
But some books just state that the pointer-to-char (char pointer) stores the address of the string literal". So just wonder how it is.
When it is used with cout, cout just treats it like a string and instead of printing the address, it just prints out all characters one by one until it reaches the terminated null character.
If this is the case, then I am just wondering how cin works with it? with a statement like this cin >> str; ?
Does the computer allocate enough memory for it? and then cin stores the first character into the first address and then advances to the next address and stores the next character?
Very new to programming, and I know that there must be another way on inputting a string into each array cells not by just inputting it one by one, but as a whole. My code at the meantime is: [URL]
I have a binary identifier which I tried to make a constexpr since all of its calculations would never occur during runtime (this is true for literal identifiers, right?). Since constant expressions can only have one instruction, I tried to cheat a little and returned an immediate call to a lambda function. This failed miserably however. I tried making a constexpr function pointer and called that from _binary down below, but the compiler still felt that it wasn't a constexpr. Why is this? And is there a way to make a function like _b below constexpr?
#include <iostream> #include <cstddef> using std::cout; using std::endl; long unsigned //Original operator"" _b(const char* const literal, size_t lsize){
In the following char array, notice the use of a backspace character in a string literal: ''.
char text1[50] = "aHello, World! Mistakee was "Extra 'e'"! ";
What exactly does a backspace character do here? When the compiler evaluates this line, does it actually delete the previous character, like when you press the backspace button on the keyboard?
The problem with that is that string.data isn't considered const during the initialization of the String struct so the compiler throws an error. It doesn't feel very elegant to do it like this either way.
Is there an elegant solution to this problem? I would like to avoid making a copy of the string literal.
I'm making a .json loader for a project that I'm working on, and to simplify things, I decided to make all the root attributes named in a separate file. Here's my problem: my loading function, Add(const char* id), works just fine when I pass it a string literal.
However, when I use a function that iterates through a vector list, even with the exact same definitions as the literal, it returns the error: std::out_of_range at memory location 0x0026fb30
I've stepped through it with the VS2010 debugger about a hundred times, checked against memory locations, and just have done everything I can think of, all to no avail..
Background: I'm using SDL and CodeBlocks and trying to make a Graphics class that would simplify some SDL operations such as drawing and loading images.
Issue: The loadImage function in the graphics class fails to load the image correctly and so the program prints out a blank window during run-time. I've tried multiple ways of passing a string literal into the function the surface temp fails to load and so background in Game fails to load. After testing it several times, I'm pretty sure that the issue lies with SDL_LoadBMP not registering the passed variable for whatever reason. I know the image is in the right place as writing SDL_LoadBMP("./Graphics/image.bmp"); brings it up just fine.
Current Code:
Main simply creates a Game object and execute(), so I didn't feel the need to put it on here.
Output: A blank window. (It should show the background image but doesn't.)
Note: I originally wrote it as gfx.loadImage(background, "./Graphics/image.bmp") but that gives me a conversion warning and still fails to show the image when the program runs. I've tried looking up examples similar to what I was doing but no one else seems to have this problem.
I thought we needed to allocate memory before assigning a value to a char* and also that we needed to use functions like strcpy() to copy something into it. Then how come this works and does not crash?
In the current code,We are using pointer of union and assigning value.
class sample { union { short *two_int; int *four_int; double *eight_real; char *one_ascii; // void *v; }; }
Than we assign value in following way.
sample.four_int[0] = (x + xoff); ( x and xoff and y and yoff all are integer) sample.four_int[1] = (y + yoff);
Than we write data into file. it was working fine into 32 bit machine but it is not working 64bit machine. When I compare data and found that data is divided by 4. For Ex The File generating from 32 bit machine contain 80 than 64 bit . File contain 20.
The StackElement class contains pointers to some dynamic arrays. When I use the assignment, StackElementArray[0] = iStackElement;, it doesn't copy the complete contents and I have to define an 'assignment operator' function to copy all the contents. I am wondering if there is a way I can assign StackElementArray[0] the pointer to the StackElement object. In that case, I will not need to copy the contents of iStackElement into StackElementArray[0] and will just copy the address.
This all compiles ok, but the last line in the code above causes a segmentation fault. I should mention Node is declared on its own in Node.h and what pgm is. including pgm.h in node.
int Allocate(int, int *); main() { int *Pointer; int Elements = 25; // this works just fine - as expected. Pointer = (int *) malloc(Elements, sizeof(int)); // This DOES NOT - The value of Pointer never changes.....
what i do with this is to stack fragments of data of type char* coming from a socket in buffer to a vector that acts as buffer, I do this since I transfer big chunks of data and the data gets fragmented by the nature of the sockets, I stack the data once its complete I retrieve the final result from the vector.
this code worked flawlessly for long time but now Im trying to port and compiler throws this error, whats the new way to assign a char array pointer to a iterator so i can stack it in the vector.
I need to dynamically build a control file for a SQL loader but when tokenizing line values read from a file i am unable to work/assign the last value to a variable even though i can print the actual token value while in the loop.
Below is the code snippet i have and get:
Code: //headElement declared as headElement[42] //getCol function is used to decode column keys present in line being read istringstream ss(line);
I'm making a game that requires the user to enter a correct username and password to play. I have a list of accepted ones saved in a txt file. How do i read each line of the file and check it with the one entered? I know how to use strcmp(string1, string2). I just need to know how to move from one line to the next. This is what I have for this part of the program so far. Also, I think im using the feof() wrong.
I need to dynamically build a control file for a SQL loader but when tokenizing line values read from a file i am unable to work/assign the last value to a variable even though i can print the actual token value while in the loop.
Below is the code:
//headElement declared as headElement[42] //getCol function is used to decode column keys present in line being read istringstream ss(line); wfile << "LOAD DATA " << endl << "INFILE * " << endl <<
const void insertStuff(const void *key, const int value){ // I want to convert the void pointer into one // of three types of pointers(int, string, or double) switch(value){ case 0: int *intPtr = key;
[Code] .....
But this causes an error of: "crosses initialization of int*intPtr"
I have to write a loop assigning a variable x to all positions of a string variable and I'm stuck. I don't have extensive experience with arrays and I'm also a bit confused about C-String. The problem is below.
"Given the following declaration and initialization of the string variable, write a loop to assign 'X' to all positions of this string variable, keeping the length the same.
char our_string[15] = "Hi there!";
(Please note this is a 'C-string', not C++ standard string.)"
I need to make a copy of a string that is defined by char *full and copy it into a different pointer defined by char *duplicate. I have written code to do this however it will not work and i cannot figure it out my code is as follows:
char *duplicate = (char *)malloc(strlen(full) + 1); strcpy(duplicate, full); /*Make second version of full*/ char *Ptr = strtok(duplicate, " "); /*Split duplicate up*/
I have a full program written but i know this is where the problem is because i have used printf statements to see where the program fails. I get no errors and it compiles successfully but it hits this point of the program and it just stops and windows automatically shuts down the program.
char *full is pointing to: "To be, or not to be? That is the question: Whether 'tis nobler in the mind to suffer The slings and arrows of outrageous fortune, Or to take arms against a sea of troubles,"
I need to duplicate the string because i need to use strtok but i will need the original string later on so i need an unaltered version.
I am trying to read the string from user and the allocate it to the another string which is ptr string but not successful . Do I have to use any dynamic memory allocation here?
Code: int main(){ char test[5]; char *strng, *base; int i; base=strng; for(i=0; i<4; i++){
In C++ there are a number of primitives that are not defined in terms of other types. By this I'm thinking
int a = 1; char b = 'M'; float c = 3.45f; short d = 0xC3A3;
Is it possible to define your own literal? What I would like to do is have a hex literal for a data type where n = sizeof(data_type). If this type were a big integer, then I would want something like:
BigInt e = 0x13CA9B0C98D983E912DA0B0A9F87E0;
My goal is to assign a value from one contingous chunk of bytes and to not do it with a string.
