Although programmers often use integers and pointers interchangeably in C, pointer-to-integer and integer-to-pointer conversions are implementation-defined . What is the difference between const int*, const int * const, and int const *? And here is a quote of the comment for more details: The best thing to do is to avoid converting from pointer type to non-pointer types. However, this is a hack; you're not supposed to be able to convert ints to pointers because in general it makes no sense. What are the differences between a pointer variable and a reference variable? From the code you have, storing a vector of pointers and printing them would be the same thing. According to the C Standard, subclause 6.3.2.3 [ ISO/IEC 9899:2011 ], Now, the opposite. Not the answer you're looking for? We use cookies to ensure that we give you the best experience on our website. Conversions between integers and pointers can have undesired consequences depending on the implementation. The main problem is that in one function, the previous coder uses a void* argument that is converted into suitable type in the function itself. How could my characters be tricked into thinking they are on Mars? We use dereference * operator, to access value stored at memory location pointed by a pointer. Appropriate translation of "puer territus pedes nudos aspicit"? Appealing a verdict due to the lawyers being incompetent and or failing to follow instructions? I need to get int from this void*, below code works fine in c but not in c++. To get a pointer to the value of no_of_records, you need to write &no_of_records. Asking for help, clarification, or responding to other answers. Pointer arithmetic. Disconnect vertical tab connector from PCB. And that part of the code is doing the opposite (e.g. What is a smart pointer and when should I use one? How does the Chameleon's Arcane/Divine focus interact with magic item crafting? If you do not have uintptr_t, then uintmax_t is not an answer either: there is no garanty you can store the value of a pointer in it! Thanks for contributing an answer to Stack Overflow! Does balls to the wall mean full speed ahead or full speed ahead and nosedive? For example, an integer variable holds (or you can say stores) an integer value, however an integer pointer holds the address of a integer variable. Value; To handle integer to object pointer conversion, use the optional integer uintptr_t or intptr_t types. To play safe, one could add anywhere in the code an assertion: With C++11, For what it's worth, suppose you don't have any headers, then define: Thanks for contributing an answer to Stack Overflow! It has found lasting use in operating systems, device drivers, protocol stacks, though decreasingly for application software. Several answers have pointed at uintptr_t and #include as 'the' solution. Why is the federal judiciary of the United States divided into circuits? Using stingstream. Method 1: Declaration and initialization: To begin, we will declare and initialize our integer with the value to be converted. Syntax stoi (str); The stoi () function contains an str argument. However, single dereference will not work when . 'size_t' and 'ptrdiff_t' are required to match your architecture (whatever it is). Typecasting: It is a technique for transforming one data type into another. in a way, both variables hold adresses :). Is it illegal to use resources in a University lab to prove a concept could work (to ultimately use to create a startup). What does "dereferencing" a pointer mean? #include <sstream>. did anything serious ever run on the speccy? This link has good info about converting to 64-bit code. Additional hint: If the number 48 should be converted to the number 0, and the number 49 should be converted to the number 1, and the number 50 should be converted to the number 2, what . Why should I use a pointer rather than the object itself? Connect and share knowledge within a single location that is structured and easy to search. What are the differences between a pointer variable and a reference variable? #include . A pointer is just a location in memory that contains a number just like any other variable. '0' is 48 so 48 - 48 is 0. int n = atoi (static_cast<const char*> (ptr)); This crashes when i run. Any idea ? error C2065: 'cout' : undeclared identifier. I am looking for a way to achieve . base is a conversion base. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Tried following code to check what happens when we convert integer pointer to a integer . Id say this is the modern C++ way. #include <iostream>. The atoi () function converts a string into an integer in the C programming language. How could my characters be tricked into thinking they are on Mars? Don't forget, you may be finding a latent bug. Example to declare constant pointer int num; int * const constant_pointer = &num; // Constant pointer to num Note: We use const keyword to declare a constant pointer. C++ How to show array element memory address in decimal (instead of hexadecimal)? It's a coincidence that pointers are quite analogous to integers. If the result cannot be represented in the integer type, the behavior is undefined. Except as previously specified, the result is implementation-defined. Find centralized, trusted content and collaborate around the technologies you use most. You should be using intptr_t. pthread_create not working. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How can I fix it? Is it correct to say "The glue on the back of the sticker is dying down so I can not stick the sticker to the wall"? Create a string representation of the number by calling a helper function with a char array via a compound literal to convert the number. int may not by large enough to store a pointer especially on 64 bit systems. I came across this question while studying the source code of SQLite. In fact, even in the pthreads case it's far more logical to pass a pointer to some structure that encapsulates the data you want to pass over. The second method is to use the atoi function included with the C standard library. Pointer(Of T) is just a reflection type used to represent pointers - they can't be used as pointers from VB.Net. There is also a good discussion of this on comp.std.c, I think the "meaning" of void* in this case is a generic handle. Why would you do that? In the sqliteInt.h, there is a paragraph of code defined a macro convert between integer and pointer. In printf, this would be %#08X, so the memory address 0x243 would be printed as 0x00000243. The chances are fair to good that my comments apply. (See also in cppreference integer types for C99 ). You can also use atoi the function to convert each character to an integer but the problem with this is that it does not protect you against overflow and underflow. The code is storing the value of an integer in a pointer. 1. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. I want to compare the dewpoint from the DHT11 to the temps on the Dallas sensors. Not the answer you're looking for? 5 Can a pointer to a void be converted to a pointer. Can virent/viret mean "green" in an adjectival sense? flaot x=1.9 int a = 1.9. now a has value of 1.it is not the correct answer.then, only we add 0.5 then convert integer. I used. Is there a verb meaning depthify (getting more depth)? Again the result is implementation-defined, but a pointer value is guaranteed to be unchanged by a round trip through an integer type. I really like using union for this sort of stuff: Thanks for contributing an answer to Stack Overflow! It's a legal conversion, if you do it right (and if the machine has. To learn more, see our tips on writing great answers. Ready to optimize your JavaScript with Rust? How did muzzle-loaded rifled artillery solve the problems of the hand-held rifle? The function takes 3 arguments, the first of which is the pointer where the string is located. 135680008 is the address in decimal (it would be 0x8165008 in hex) to which p is pointing: the address of the memory area allocated with malloc. There are few ways of converting string to integer values using C: The first method is to manually convert the string into an integer with custom code. How to convert a factor to integer\numeric without loss of information? On my particular instance my int is 32 bit and the pointer is 48 bit. Consequently, converting directly from a char * pointer to a uintptr_t, as in this compliant solution, is allowed on implementations that support the uintptr_t type. I've tried the following: void *value = 0x00323c68; but I get a typecasting error. Can a local variable's memory be accessed outside its scope? In printf, this would be %#08X, so the memory address 0x243 would be printed as 0x00000243. Need to declare a pointer before using it to store any variable address. I have the dewpoint converted to an integer but when I try to convert the dallas sensors to an integer I keep running into issues. How to cast integer value to pointer address? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. I don't really know what the question is here. reinterpret_cast is better than C style cast, the reason : I tried that just now, I think the output it gave was different from the pointer address. What is a smart pointer and when should I use one? Value at address contained in b is an integer. (See also in cppreference integer types for C99). These types are defined in <stdint.h> for C99 and in the namespace std for C++11 in <cstdint> (see integer types for C++ ). Is it cheating if the proctor gives a student the answer key by mistake and the student doesn't report it? If you meant to include , you probably also want to use std::uintptr_t instead. so the right way to store a pointer as an integer is to use the uintptr_t or intptr_t types. 2 Can you cast a pointer to an integer in C? To learn more, see our tips on writing great answers. I am trying to adapt an existing code to a 64 bit machine. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. C pointer to array/array of pointers disambiguation. Correct to use reinterpret_cast. Or do you mean. @user1934608: Its not guranteed to be big enough. When assigning the pointer, the integer value i will represent the lowest 32 bit of the pointer. The strtol function is part of the C standard library, and it can convert char* data to long integer value as specified by the user. Is there a higher analog of "category with all same side inverses is a groupoid"? If 0x80 was not derived from a valid uint32_t *, the result in undefined behavior (UB). Thanks for contributing an answer to Stack Overflow! But not the int. So, if 'b' is a pointer to 'a' and the value of 'a' is 10 and its address is 9562628, then 'b' will have a value 9562628 and its address will be . these types are defined in for C99 and in the namespace std for C++11 in (see integer types for C++ ). One approach is to use the ASCII approach where you take the character itself and subtract it based on its value. How can I use a VPN to access a Russian website that is banned in the EU? 2 days ago. In this example, we are going to make use of the sprintf () function from the C standard library. char arrc [10]; int i = 5429; sprintf (arrc,"d",i ); Just like printing in the output screen, you can print on any string you want. Find centralized, trusted content and collaborate around the technologies you use most. There are four arithmetic operators that can be used in pointers: ++, --, +, -. How does legislative oversight work in Switzerland when there is technically no "opposition" in parliament? so the right way to store a pointer as an integer is to use the uintptr_t or intptr_t types. Asking for help, clarification, or responding to other answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. EDIT: Chapter 7.20.1.4 "Integer types capable of holding object pointers" of the same standard says: The following type designates a signed integer type with the property that any valid pointer to void can be converted to this type, then converted back to pointer to void, and the result will compare equal to the original pointer: What is the rule for why this pointer value can't be converted to an integer? i am doing this inside a function which needs to return the pointer. 4 How to cast integer value to pointer address? In C++ there are different types of casts, but reinterpret_cast is the correct cast for this conversion (see also here). Would it be possible, given current technology, ten years, and an infinite amount of money, to construct a 7,000 foot (2200 meter) aircraft carrier? Alternatively, you can download Microsofts version of the stdint.h file from here or use a portable one from here. (Don't use magic numbers like 49) - Shawn. Making statements based on opinion; back them up with references or personal experience. Typecast the character to convert character to int using int. It's not always so simple as to look at code (including when compilers warn about it) that uses a signed int but is used for a size and think it okay to change it to unsigned. p: is pointer to 0 th element of the array arr, while ptr is a pointer that points to the whole array arr.. Convert int to string in C using sprintf () function The C library sprintf () function allows us to convert integers into a formatted string. : #include <pthread.h> #include <stdio.h> #include <stdlib.h> #define NUM_THREADS 5 int. The below diagram explains the concept of Double Pointers: The above diagram shows the memory representation of a pointer to a pointer. Why / when to use `intptr_t` for type-casting in C? To ensure it is defined in a portable way, you can use code like this: Just place that in some .h file and include wherever you need it. We can convert a char to string first and then use the stoi () to convert the string to an integer. Any links provided related to this topic would also be helpful. They are set as pointers and I don't know how to convert to integer. Creating Local Server From Public Address Professional Gaming Can Build Career CSS Properties You Should Know The Psychology Price How Design for Printing Key Expect Future. Cooking roast potatoes with a slow cooked roast, 1980s short story - disease of self absorption. Ready to optimize your JavaScript with Rust? Does the collective noun "parliament of owls" originate in "parliament of fowls"? While size_t is usually large enough to hold a pointer, it's not necessarily the case. Print the integer using cout. A pointer is a variable that stores the address of another variable. I think you missed the point on my question. Then convert the void * to the desired type. Connect and share knowledge within a single location that is structured and easy to search. Easiest way to convert int to string in C++. It can also convert a negative number. Note that this char pointer argument is not modified and has a const qualifier. rev2022.12.9.43105. Is it possible to convert an integer to a pointer? However, this is clearly not possible in your case. Why is this usage of "I've to work" so awkward? ; We know that the pointer arithmetic is performed relative to the base size, so if we write ptr++, then the pointer . Unlike other variables that hold values of a certain type, pointer holds the address of a variable. On my particular instance my int is 32 bit and the pointer is 48 bit. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. C (pronounced like the letter c) is a middle-level, general-purpose computer programming language.It was created in the 1970s by Dennis Ritchie, and remains very widely used and influential.By design, C's features cleanly reflect the capabilities of the targeted CPUs. Not the answer you're looking for? Power Function in C/C++ INT_MAX and INT_MIN in C/C++ and Applications Taking String input with space in C (4 Different Methods) Pointer to an Array | Array Pointer Modulo Operator (%) in C/C++ with Examples Memory Layout of C Programs Static Variables in C Functions in C++ TCP Server-Client implementation in C C Program For Char to Int Conversion Since int *ip; is a pointer to an integer and int thatvalue = 1; is an integer, assuming you want the value stored at the address pointed to by ip assigned to thatvalue, change thatvalue = ip; to thatvalue = *ip; (note the addition of the dereference operator * to access a value equivalent to the value at the pointer address). it printed: "2293616" and "0x22ff70" all I did was replaced the line, this is the same number : 2293616 = 0x22ff70. Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not? Cooking roast potatoes with a slow cooked roast. To convert a string to an integer, you can use the library function atoi (). We are typecasting integer N and saving its value in the data type char variable c. Print the character: Finally, print the character using print. 1980s short story - disease of self absorption. Why is apparent power not measured in Watts? It would be better to declare Value with a pointer type in the first place: uint32_t *const Value = (uint32_t *) (uintptr_t)0x80; because then you only have to write the casts when you initialize it, not when you use it, *Value = 2; and you probably have a bunch of places where you use it. Why is Singapore considered to be a dictatorial regime and a multi-party democracy at the same time? central limit theorem replacing radical n with n, TypeError: unsupported operand type(s) for *: 'IntVar' and 'float'. In C++ you can do this by hackery; C-style casts are an example of this hackery, and in fact your program works as desired: #include <iostream> using namespace std; int main () { int *NumRecPrinted = NULL; int no_of_records = 10; NumRecPrinted = (int*)no_of_records; cout << "NumRecPrinted!" It is also an easiest way to convert other data types to string values in C++. Method 1: Using to_string () and c_str () In this method, we first convert the given number into a c++-string and then transform it into the char* type using the c_str () method. Does balls to the wall mean full speed ahead or full speed ahead and nosedive? The string will be valid for the function and to the end of the block of code. Using Boost's lexical_cast () function. Why is the federal judiciary of the United States divided into circuits? Algorithm of the stoi () function Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not? Connect and share knowledge within a single location that is structured and easy to search. 3 How do I cast a void pointer to integer? How to store a pointer as an integer in C + +? Syntax to declare constant pointer <pointer-type> * const <pointer-name> = <memory-address>; Note: You must initialize a constant pointer at the time of its declaration. How to set a newcommand to be incompressible by justification? But, @LokiAstari: It's important to distinguish between, @GManNickG thankyou, I wasn't aware of that. What is this fallacy: Perfection is impossible, therefore imperfection should be overlooked. Converting from unsigned Char* to unsigned int. The text was updated successfully, but these errors were encountered: Copyright 2022 it-qa.com | All rights reserved. Transferring that analogy to your program: you are converting the object pointing to your int to an int itself. It would be better to locate a stdint.h header (if your compiler doesn't already have one) and use uintptr_t. Easiest way to convert int to string in C++. A concrete example of, the only answer which properly mentions reinterpret_cast. Is it illegal to use resources in a University lab to prove a concept could work (to ultimately use to create a startup). Why would Henry want to close the breach? The rubber protection cover does not pass through the hole in the rim. If it is holding an integer value, it had better be within integer range! Why are you trying to do that, anyway you just need to cast, for C code : If your writing C++ code, it is better to use reinterpret_cast. Then convert the void * to the desired type. A short example: Of course, on a 64 bit machine, I get the error: I would like to correct this so that it still works on a 32 bit machine and as cleanly as possible. The code inside my function() would work if the calls were written: Since yours are probably written differently, you need to review the points where the function is called to ensure that it makes sense to use the value as shown. Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not? int **d_ptr = &ptr; // pointer to a pointer declared // which is pointing to an integer. The str string is passed inside the stoi () function to convert string data into an integer value. Why does setupterm terminate the program? Any pointer type may be converted to an integer type. (See also in cppreference integer types for C99 ). 3. x - '0' where x is '0' through '9' will always work in C. ASCII or not. In C we access the registers by casting the address to struct pointers which are evaluated at compile time. but int is exactly 4294967295 in size, and thats the equivellent of FFFFFFFF in hex, and aren't pointers just holding the address of a number in memory which is somewhere between 00000000 and FFFFFFFF? 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