By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. But if you insist on managing memory by yourself, you have to manage it completely. pointers - Copy char* in C - Stack Overflow Next I put (char *)string.c_str () but this only causes an unhandled exception. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The difference is the {} at the end of char c[256]{}. (IMHO std::remove (const char*) should be std::remove_file (std::string const&) or at least std::remove_file (const char . Understand but if I write the code like this it works: Only because you have not changed the code since then. Why is char[] preferred over String for passwords? - Mike Seymour Dec 13, 2013 at 7:37 According to the documentation ( msdn.microsoft.com/en-us/library/kdzttdcb.aspx) beginthreadex wants a void*. Without any attempt at completeness or educational direction, here's a version of your code that should work. Short story about swapping bodies as a job; the person who hires the main character misuses his body. Something without using const_cast on filename? @MarcoA. Edit: Even better use strdupas Miroslav suggests. That means for every character copied from s to c there was a wasted effort clearing the character to zero at the beginning. In conclusion, converting a const char* to a char* in C++ is a relatively simple task that can be accomplished using the const_cast operator, the strcpy() function, or the memcpy() function. rev2023.4.21.43403. The hyperbolic space is a conformally compact Einstein manifold. So the C++ way: There's a function in the Standard C library (if you want to go the C route) called _strdup. Even when you do, you will probably overwrite unallocated memory when you attempt to set the string terminator. You have to decide whether you want your file name to be const (so it cannot be changed) or non-const (so it can be changed in MyClass::func). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why is it shorter than a normal address? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I'm very new to C, I'm getting stuck using the strncpy function.\. In C++, you should use the safer and more elegant std::string: a's content, as you posted, points to a read-only memory location set up by the compiler. Finally I just tried char *test = string.c_str () but that's not compatible with const either. Is safe but slower. Otherwise go for a heap-stored location like: You can use the non-standard (but available on many implementations) strdup function from : or you can reserve space with malloc and then strcpy: The contents of a is what you have labelled as * in your diagram. But I agree with Ilya, use std::string as it's already C++. without allocating memory first? Parabolic, suborbital and ballistic trajectories all follow elliptic paths. new_name). Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? A minor scale definition: am I missing something? Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? It's trivial to pass a single char as a parameter, so it's far more likely that the function takes in a pointer to a null-terminated string. Allocate enough to hold the string you are copying into it. You need to pre-allocate the memory which you pass to strcpy. What should I follow, if two altimeters show different altitudes? If you make any changes, particularly adding a new string constant before "Test", you will find that the pointer you stored in EEPROM points to where "Test" used to be. How can I convert const char* to char[256]. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Does the C++ standard allow for an uninitialized bool to crash a program? So now what s points to is undefined, If you were not creating the string in that line it would be safe. Asking for help, clarification, or responding to other answers. How to append text to a text file in c++? I compiled very simple code, but I couldn't compile this code. To learn more, see our tips on writing great answers. Looking for job perks? so now if we change the size of c the code will still work. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. What was the actual cockpit layout and crew of the Mi-24A? #include <algorithm>. You can implicitly convert char * into const char *. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? Why did DOS-based Windows require HIMEM.SYS to boot? Looking for job perks? @gman Potentially, the optimal answer is still to not use. String literals are constant and shouldn't be modified, older compilers might allow assigning them to char * but more modern compilers will only allow assignment to const char* (or const char[]), e.g. Is there a weapon that has the heavy property and the finesse property (or could this be obtained)? c - Using strncpy() to copy const char * - Stack Overflow rev2023.4.21.43403. thank you for this explanation, it really helps. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. doesn't copy or write more characters than necessary). rev2023.4.21.43403. Connect and share knowledge within a single location that is structured and easy to search. I.e. First of all the standard declaration of main looks like. Why typically people don't use biases in attention mechanism? P.S. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Find centralized, trusted content and collaborate around the technologies you use most. How can I control PNP and NPN transistors together from one pin? You need to do that before you copy to it. The first method uses C++ type casting feature called const_cast, it allows you to remove the const-ness of a variable, so you can modify it. Hi, I have to replace a string value in a specific char* array and then write it in eeprom: char * MyEepromArray[12]; //array char String Valore;// string value to insert in array location coming from serial MyEepromArray[2]=Valore.c_str();// i convert String to const char* an put it on array position 2 EEPROM.put(0, MyEepromArray); //I write the whole array in eeprom but the eeprom is not . Why do men's bikes have high bars where you can hit your testicles while women's bikes have the bar much lower? One other issue is using magic numbers. a is your little box, and the contents of a are what is in the box! That's why the type of the variable is const char*. Short story about swapping bodies as a job; the person who hires the main character misuses his body, if the result is too long, the target string will not be nul-terminated. Can my creature spell be countered if I cast a split second spell after it? Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? There are many different ways to copy a const char* into a char[]: Is bad code. How a top-ranked engineering school reimagined CS curriculum (Ep. char const* implies that the class does not own the memory associated with it. To learn more, see our tips on writing great answers. Also you can not use strings as switch/case labels. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. awesome art +1 for that makes it very clear. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. If you want to have another one at compile-time with distinct values you'll have to define one yourself: Notice that according to 2.14.5, whether these two pointers will point or not to the same memory location is implementation defined. In your first example, tmp is an lvalue of type mutable pointer to const char, so a reference can be bound to it without issue. What is this brick with a round back and a stud on the side used for? Does a password policy with a restriction of repeated characters increase security? Even better, use implicit conversion: filename = source; It's actually not conversion, as string has op= overloaded for char const*, but it's still roughly 13 times better. What was the actual cockpit layout and crew of the Mi-24A? This is considered bad practice, but you should think of const as a strong suggestion of the original programmer, not to modify it. Here, the '1234' does not denote a string. Getting a "char" while expecting "const char", Using an Ohm Meter to test for bonding of a subpanel. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, problems with convert const char* to char* in c, https://stackoverflow.com/questions/252782/strdup-what-does-it-do-in-c.