C/C++ :: SDL LoadBMP Fails To Load A Passed String Literal
Jan 24, 2014
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'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..
What shall I learn in order to send values from 0.00 to 5.00? I'm working with they Hitachi 16x2 LCD display.I've been sending/displaying literal values on it all day.
Code:
SendCharater(unsigned char val)
where the variable val corresponds to the LCD character table.I can also send Hello World to the display, like so:
Code:
void putsXLCD(unsigned char *buffer){ while(*buffer) // Write data to LCD up to null { while( BusyXLCD() ); // Wait while LCD is busy SendCharacter(*buffer); // Write character to LCD buffer++; // Increment buffer } return; }
I could type in putsXLCD("5.00") in order to display it on the LCD, but how do I implement this automatically for values, e.g. 0.00 to 5.00?It appears I can only pass literal values through the function SendCharacter, meaning that in order to display "0" I have to pass the value 0x30 (the hex value of "0" on the LCD Table).
My current thought process:Much like passing "Hello World" in the function putsXLCD(), I need to assign a pointer that points at each value in the "array" that I need to send. E.g., I need to send 3.24, so I need to point to "3", fetch the corresponding hex value in the LCD table, in this case 0x34, and the pass this 0x34 into the SendCharacter function, and so on. So, if this is the case, how can I fetch the corresponding hex value?
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 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 */
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?
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?
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 have a list of Strings that are passed to a method consecutively by reference from a class. I want to get the string value passed to the method at a point in time. The reason is to perform an if statement.
//this is the class that holds that holds the constants. using System; using Microsoft.VisualStudio.TestTools.UnitTesting; namespace xxx.Functional.xyz.Login { public class Constants { public static String Username = "paul"; public static String Code = "4";
I am posting this simplified piece of code that is a bit confusing for me. There are two functions that I call. One shows the expected results but the result of the other one rather puzzles me.
Calling the function sum1 does not change the values stored in the variables val1 and val2. The output of the program is as follows:
val1= 1 ## val2= 10 // before the call of function sum1 val1= 1 ## val2= 10 // after the call of function sum1 sumOfVals= 22
This is quite obvious and as expected and I just pasted this piece of code as an example for better clarification.
However, if I call the function buildLaplacianPyramid and apply a function for Gaussian Blurring, this also effects the cv::Mat passed to the function. The line imshow("M1, after buildLaplacianPyramid",M1); therefore shows an image that is blurred. Since I am not passing a pointer to the cv::Mat I do not understand why this should be happening. I was assuming that there would be a copy of the cv::Mat M1 to be used within the function. Therefore I was expecting the cv::Mat M1 to retain its original value. I was expecting that all changes applied to cv::Mat inputmat within the function would not have any influence on the cv::Mat M1. Just like in my other example with the sum.
I want to create 2 functions to (1) convert a passed string into proper case (capitalize the first alpha character of a string and every alpha character that follows a non-alpha character); (2) sort the array of names (after it has been converted to proper case).
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.
these function works. but if i concat literal strings with '+', i must use '(string)'. so i'm trying overload the operator + for concat literal strings, but without sucess:(
"A constant, like a variable, is a memory location where a value can be stored. Unlike variables, constants never change in value. You must initialize a constant when it is created. C++ has two types of constants: literal and symbolic.
A literal constant is a value typed directly into your program wherever it is needed. For example, consider the following statement:
long width = 5
This statement assigns the integer variable width the value 5. The 5 in the statement is a literal constant. You can't assign a value to 5, and its value can't be changed.
The values true and false, which are stored in bool variables, also are literal constants.
A symbolic constant is a constant represented by a name, just like a variable. The const keyword precedes the type, name, and initialization. Here's a statement that sets the point reward for killing a zombie:
const int KILL_BONUS = 5000;
Whenever a zombie is dispatched, the player's score is increased by the reward:
playerScore = playerScore + KILL_BONUS;
If you decide later to increase the reward to 10,000 points, you can change the constant KILL_BONUS and it will be reflected throughout the program. If you were to use the literal constant 5000 instead, it would be more difficult to find all the places it is used and change the value. This reduces the potential for error."
what's the difference? Here is a program to demonstrate what I'm having trouble conceptualizing.
#include <iostream> using namespace std; int main() { int width = 10, length = 10; int area = width * length; cout << "Width: " << width << endl; cout << "Length: " << length << endl; cout << "Area: " << area << endl; return 0; }
Now, why would it be harder to go in and changed a regularly defined integer than one defined with the 'const' keyword proceeding it? For example, the width and length variables. My confusion comes from the point that they seem to both simply be variables with a value assigned to them. I feel as if the process of having to change a literal constant's value is synonymous to the process of having to change a symbolic constant's.
I`ve wrote a function for my utility to XOR char* buffer by a key, then to reverse it with the same key. Here is the code, it`s simple enough:
Code:
static inline char* XOR_buffer(const char* d, const char* k ) { char *newstr = (char*) malloc(sizeof(char)* strlen(d)); newstr[0]=''; printf("%d is size of string ", strlen(d)); char *begin = newstr; char* ret = begin; int len = strlen(k); }
[code]....
The lengh of the string is reduced by the second XOR call. You can try it out, just define XORDBG to view the error message in the second pass to the buffer.
i created an com client that try to create com server with the command CreateInstance. at win 7 it works fine (both 32 and 64 bit). but with xp it fails. i created the app with win 7 - 64 bit.
When I ran it only the calls from doers array is called 7 times normally, and donters only one time. Why is that? When I call doers from the second loop, it prints the doers functions again....and only one call to donters is made to the first static inline donter functions __dont1()...
What I have is a main function that takes input characters from the command prompt during the main function call, and coverts it to an integer array a using atoi. (starting at the 2nd character - the 1st is reserved for another call that I plan to reference later, and the 0th is obviously the ./function). A function is then called to find the mode of an array (the range of values in the array is 1-30). Now, when I run the whole thing, I get a segmentation fault (core dumped) for even number of arguments. It's late and I've been staring at it for too long...
Code: #include <stdio.h> #include <stdlib.h> int get_mode(int a[], int count);
I'm trying to write a piece of code that calculates the difference in days between two manually input dates. The part of my code that's causing problems is:
xxx
When running the code and prompted to enter the date, if I input for example 31/12/2014, it'll be rejected and send me back to the beginning of the loop. Any date with 31 days involving months 1, 3, 5, 7, 8, 10 or 12 causes this problem. All other valid dates however work perfectly fine (e.g. 30/4/2014).
Something possibly worth mentioning is that, when I take out all other conditions from the loop, i.e.
xxx
it works fine (31/12/2014 is accepted), but of course I need all of the other conditions in there too.
I have a quick question about dynamic memory. I know that if you are dynamically allocating memory for a single data array and it fails, you can immediately abort the program via a return statement, but is this also true with multiple data arrays? For instance:
int *foo, *bar foo = new (nothrow) int [5]; bar = new (nothrow) int [5]; if (foo == nullptr || bar == nullptr) return -1; else /*rest of execution */
If the answer to the previous question is no, do you need to do a delete[] on the arrays that succeeded before terminating the application? Say foo is correctly allocated but bar fails, would you have to do something like this?
int *foo, *bar foo = new (nothrow) int [5]; bar = new (nothrow) int [5]; if (foo == nullptr || bar == nullptr) { if (foo == nullptr && bar != nullptr) delete[] bar;
