(See INT36-EX2 .) The problem is that converting a void* pointer to unsigned int is inherently non-portable. // It is valid and converting it back to a pointer is also OK . If there a problem, it returns -1 but preseted as pointer. After it initializes a String object and gets its length, it does the following: Calls the Marshal.StringToHGlobalAnsi method to copy the Unicode string to unmanaged memory as an ANSI (one-byte) character. Converts the string representation of a number in a specified style to its signed native integer equivalent. Converts the read-only span of characters representation of a number in a specified style and culture-specific format to its signed native integer equivalent. Other conversions between pointers and integers are allowed to behave differently, however. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. View more solutions 245,202 Related videos on Youtube 08 : 14 Serialization - A Crash Course (as in p = (void*) 42; ). Tries to write the current value, in little-endian format, to a given span. Not sure if it was just me or something she sent to the whole team. Initializes a new instance of IntPtr using the specified 64-bit signed integer. Is there any reason on passenger airliners not to have a physical lock between throttles? A few takeaways: C - Why cast to uintptr_t vs char* when doing pointer arithmetic, port70.net/~nsz/c/c11/n1570.html#7.20.1.4. Is Energy "equal" to the curvature of Space-Time? To learn more, see our tips on writing great answers. The C code's integers and floating-point values are mapped to Python's regular int, long and float.Moreover, the C type char corresponds to single-character strings in Python. Remember that in C++ one cannot perform bitwise operations on pointers. Using IntPtr as a pointer or a handle is error prone and unsafe. 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"? Unfortunately, the Standard provides no means of testing at compile time whether an implementation behaves in a fashion consistent with those for which C language was originally designed, and supports all the constructs implied by such behavior. Converts the value of this instance to a 32-bit signed integer. Received a 'behavior reminder' from manager. @chux, Yes, this is not portable in some limited case. The following type designates an unsigned 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 C11dr 7.20.1.4 1. A read-only field that represents a signed integer that has been initialized to zero. uintptr_t is an alias ( typedef) of an unsigned integer which has the same size of a pointer (Note that intptr_t / uintptr_t is optional in C++11). Any pitfalls using char* instead of void* when writing cross platform code? Next in thread: Joe Perches: "Re: [PATCH 2/8] vop: Cast pointers to uintptr_t" Messages sorted by: Fix these on 32-bit: vop_vringh.c:711:13: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast] Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> . Gets the length, in bits, of the shortest two's complement representation of the current value. It might be larger. The C Standard guarantees that a pointer to void may be converted to or from a pointer to any object type and back again and that the result must compare equal to the original pointer. I am speaking about handles which are used in Windows to work with various system objects. Ready to optimize your JavaScript with Rust? Passing pointers between methods can cause undefined behavior. Microsoft makes no warranties, express or implied, with respect to the information provided here. Gets the smallest possible value of IntPtr. Why is apparent power not measured in Watts? Thus the uintptr_t give you a machine independent way of debugging your code before you try deploying to target hardware. It has been many years since I even looked at intel-16bit stuff but segments do make a mess of things. There are times where you need to play with the bits, and it would normally generate compiler errors. In theory, there might not be an integer type that can hold any pointer converted to an integer (so the type uintptr_t might not exist). In general, you should not treat NULL as "an address 0", but as a special pointer that points to nowhere and crashes your program when dereferenced. Relying on meaningful, stable values for pointers cast to uintptr_t/intptr_t is conforming even if your program may exhibit bugs on some implementations. The method returns an IntPtr object that points to the beginning of the unmanaged string. Computes the number of leading zeros in a value. What are the differences between a pointer variable and a reference variable? Find centralized, trusted content and collaborate around the technologies you use most. How to allocate aligned memory only using the standard library? Storing integers in double type 5. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Do not use uintptr_t for pointer arithmetic if you care about the portability of your code. If you mean assigning a pointer to one type of int to a pointer to anther type of intwith casting, well . Bottom line: If you need pointer arithmetic, use pointer arithmetic. First thing, at the time the question was asked, uintptr_t was not in C++. It is used to determine the offset into unmanaged memory to which the next character in the ANSI string is copied. If you should have any questions prior to buying, please do not hesitate to contact me. What is the difference between #include and #include "filename"? Connecting three parallel LED strips to the same power supply. Message ID: 20220612213227.3881769-3-willy@infradead.org (mailing list archive)State: New: Headers: show Initializes a new instance of IntPtr using the specified 32-bit signed integer. If, for some reason, the programmer needs to store pointers in integer types, he may use memsize-types for that - for instance, intptr_t, size_t, INT_PTR, etc. Unit testing on actual target hardware is a hassle so I typically write everything on an Intel based PC either in Windows or Linux using Ceedling and GCC. A common reason to want an integer type that can hold an architecture's pointer type is to perform integer-specific operations on a pointer, or to obscure the type of a pointer by providing it as an integer "handle". How do you cast a char* to IntPtr? But when I read your comment I add "#include " and yeah now it works. (correct me if I'm wrong) on 64-bit systems, sizeof (int *) = 8. next prev parent reply other threads:[~2022-02-10 15:43 UTC|newest] Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-04 17:42 [PATCH 0/7] Verify C++ compatibility of public headers Bruce Richardson 2022-02-04 17:42 ` [PATCH 1/7] eal: fix header build with C++ Bruce Richardson 2022-02-04 17:42 ` [PATCH 2/7] eventdev:" Bruce Richardson 2022-02-07 9:40 ` Jerin . Still I do not see the need of pointer at all. Clamps a value to an inclusive minimum and maximum value. You have to use uintptr_t to make sure that your pointers are getting typecasted to the right integer size. Of course you could do that, but that would of course be undefined behavior. Copies the sign of a value to the sign of another value. On machines that have self-aligned types the two least significant bits of a pointer are going to be zero (because addresses are multiples of 4 or 8). So far I am using void* for storing adresses and cast those to char* if I need to change them (add offset or modify in general), I have heard of that type defined in stdint.h but I don't see the difference in using it for pointer arithmetic over the char* conversion (which seems more C89 friendly atleast to me). Advent Of Code Day 1 to 5 using only the C Preprocessor. In .NET 5 and later versions, this type also implements the IFormattable interfaces. Condition is Used. On those machines the compiler may not even allow casting between the two classes, but uintptr_t should be able to hold either. I write mostly embedded code targeted at various arm and currently tensilica processors. How to connect 2 VMware instance running on same Linux host machine via emulated ethernet cable (accessible via mac address)? At what point in the prequels is it revealed that Palpatine is Darth Sidious? 0x80 represents an address in the memory e.g. Converts the value of this instance to a 64-bit signed integer. The vast majority of programs have no need to cast pointers to integers. Find centralized, trusted content and collaborate around the technologies you use most. Note: The C99 types intptr_t and uintptr_t, declared in <stdint.h>, are respectively signed and unsigned integer types capable of representing pointer values. So cast to uintptr_t is a good idea. Find centralized, trusted content and collaborate around the technologies you use most. Disabled warnings 2. For reasons see Why can't you do bitwise operations on pointer in C, and is there a way around this? uintptr_t definition is apparently not obligatory (so not standard) even in C++11! A return value indicates whether the conversion succeeded. The offsetof macro, inherited from C and applicable to standard-layout classes (and, conditionally, other classes) in C++, calculates the layout offset of a member within a class. unsigned integer type capable of holding a pointer to void uintptr_t can be used in the following way: NULL or 0 or (void *)0 are just different ways of getting a null pointer. Yet it sounds like OP is on a platform with memory mapped data locations. Payment is required within 48 . Thus, different casting is needed. Thank you for very details behind this decision. Thus in order to do bitwise operations on pointers one would need to cast pointers to type uintptr_t and then perform bitwise operations. (Incidentally, gcc has an extension that permits pointer arithmetic on void*. You can't apply the indirection operator to a pointer of type void*. At what point in the prequels is it revealed that Palpatine is Darth Sidious? Bit shifting operations 6. I've seen programs that exploit this to compress data.. @saadtaame: I just pointed out that this is UB, It's not necessarily exactly the size of a pointer. Converts the string representation of a number to its signed native integer equivalent. Indicates whether the current object is equal to another object of the same type. Use this cast carefully. The hardware had 64-bit words, with a machine address containing the address of a word. A return value indicates whether the conversion succeeded. I will try to address the "what it can be used for?" Basically I just need to know if this yields. It's an unsigned integer type exactly the size of a pointer. const_cast const_cast adds or removes const from a variable. What do you want to check at compile time exactly? Calls the Marshal.AllocHGlobal method to allocate the same number of bytes as the unmanaged string occupies. Uses a loop to copy each character from the string to the unmanaged block of memory. How to use a VPN to access a Russian website that is banned in the EU? Initializes a new instance of IntPtr using the specified pointer to an unspecified type. To learn more, see our tips on writing great answers. Second, convert the result to target integer. Not sure if it was just me or something she sent to the whole team. Represents a signed integer where the bit-width is the same as a pointer. It doesn't say anything about size. I've asked the OP for clarification. I want to be able to quit Finder but can't edit Finder's Info.plist after disabling SIP. Many C++03 compilers do provide that file. Working with pointers, structures and arrays . Converts the value of a 64-bit signed integer to an IntPtr. When you convert an open pointer that contains a valid space address, the return value is the offset that is contained in the address. In the past, I've cast the pointer to an unsigned int like this: char *ptr = 0x1234; printf ("ptr is 0x%x\n", (unsigned int)ptr); A 16-bit compiler may be just fine with this, but it would generate warnings on a 32 or 64-bit compiler because the "int" is a "long" or "long long" to them. And also you can change your ID to be uintptr_t too: it is an integer in the end. You should be using intptr_t. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Why is processing a sorted array faster than processing an unsorted array? Do not use uintptr_t for pointer arithmetic if you care about the portability of your code. <p dir="ltr">ANTUQUE CAST ALUMINUM HUNTING POINTER BIRD DOG ASHTRAY 1906. It would be better to declare Value with a pointer type in the first place: because then you only have to write the casts when you initialize it, not when you use it. Then, can NULL be checked whether it is equal to 0 or not? Converts the numeric value of this instance to its equivalent string representation using the specified format and culture-specific format information. Running the risk of getting another Necromancer badge, I would like to add one very good use for uintptr_t (or even intptr_t) and that is writing testable embedded code. uintptr_t ptr = reinterpret_cast<uintptr_t>(p); reinterpret_cast cannot cast away const or volatile. Magic numbers 4. Obtain closed paths using Tikz random decoration on circles, If you see the "cross", you're on the right track, central limit theorem replacing radical n with n, Better way to check if an element only exists in one array. It is not guaranteed by the C standard, but in practice yes, on most platforms null is represented as all-bits-zero. It's the. so, im trying to compile my graphic-engine but I get 2 warnings about the same thing. Does a 120cc engine burn 120cc of fuel a minute? opengroup.org/onlinepubs/000095399/basedefs/stdint.h.html. This matches the original libunwind API. My application didn't compile because of uintptr_t declaration. Debian/Ubuntu - Is there a man page listing all the version codenames/numbers? A return value indicates whether the conversion succeeded. To handle integer to object pointer conversion, use the optional integer uintptr_t or intptr_t types. The only guarantee that the C standard provides is that you can convert a void* value to uintptr_t and back again, and the result will compare equal to the original pointer value. How to smoothen the round border of a created buffer to make it look more natural? Any pointer is castable to. How should i use (uintprt_t)? c; cpp; After displaying the original and reversed strings, all examples call the FreeHGlobal method to free the memory allocated for the unmanaged ANSI string and the unmanaged block of memory. There have been some systems where the natural representation for a null pointer was, for various reasons, something other than all-bits-zero, and the Standard makes allowances for them. The offset is incremented with each iteration of the loop. Connect and share knowledge within a single location that is structured and easy to search. it should compile without errors. Name of a play about the morality of prostitution (kind of), Sed based on 2 words, then replace whole line with variable, Sudo update-grub does not work (single boot Ubuntu 22.04), Typesetting Malayalam in xelatex & lualatex gives error. Thanks! It's a specialized and unusual feature, which is why it's optional and has loose semantics. Further, even if pointers are representation-compatible, an implementation need not make allowances for usage scenarios beyond those mandated by the Standard. Why is char[] preferred over String for passwords? Asking for help, clarification, or responding to other answers. This was common practice before the advent of 64-bit machines and it is not safe or reasonable. Is there any reason on passenger airliners not to have a physical lock between throttles? Another common use case of casting a pointer to an int is to create an opaque handle that hides the pointer. What you say is true, but I am not going to change my answer because (a) I think that will just confuse OP further, and (b) an ABI where, As I said, I am not going to insist. C++ std::uintptr_t prec = reinterpret_cast<uintptr_t>(&(a[0])); Previous Next. Query the alignment of a specific variable, Setting a buffer of char* with intermediate casting to int*. Tutorial: Compile-Time RNG Upvote 0 syntaxerror Why is Singapore considered to be a dictatorial regime and a multi-party democracy at the same time? No other C++ cast can add or remove these keywords. Why do American universities have so many general education courses? I am working on a programm where I have to modify the target process memory/ read it. Similarly, the C type wchar_t corresponds to single-character unicode strings. Is it cheating if the proctor gives a student the answer key by mistake and the student doesn't report it? Take this to mean what it says. Also we do things in unit testing that we would never do in production because breaking things is good. No other type is officially guaranteed to have this property; however, "cpp plus 1" is correct that size_t usually also does. uintptr_t is an unsigned integer type that is capable of storing a data pointer (whether it can hold a function pointer is unspecified). Content of mfbt/ThreadLocal.h at revision 7131c65c0d4a7fa5155d046a66a655c28693dafe in mozilla-esr52 It is optionally defined in C++11 and later standards. Would salt mines, lakes or flats be reasonably found in high, snowy elevations? Why did the C language add keywords for complex numbers Can you give me some proof that storing multidimansional What is the best way to easily indicate that a variable Is a pointer pointing on something unintended a problem With a C program, should I save files with or without an Can you utilize the overflow feature of unsigned types to How did C do atomic operations before including the Press J to jump to the feed. How can one print a size_t variable portably using the printf family? 1980s short story - disease of self absorption, What is this fallacy: Perfection is impossible, therefore imperfection should be overlooked. Pointers to functions need not be convertible to the uintptr_t type though again they most often are convertible. Using pointers for this is invalid. Why is this usage of "I've to work" so awkward? This type implements the ISerializable. In comments user R.. points out that the following is likely incorrect if the addresses the code is dealing with are not valid within the current process. Reasons for this pointer insanity. A void pointer is declared like a normal pointer, using the void keyword as the pointer's type: void* ptr; A void pointer can point to objects of any data type: Compares two values to compute which is lesser. The subreddit for the C programming language, Cast Object to MyGenericClass if you have Class. Ready to optimize your JavaScript with Rust? Why can't you do bitwise operations on pointer in C, and is there a way around this? Converts the value of the specified IntPtr to a 32-bit signed integer. Applying the indirection operator to a null pointer causes an implementation-defined behavior. . Penrose diagram of hypothetical astrophysical white hole. What is uintptr_t and what can it be used for? What is the difference between String and string in C#? Was pointed out by @chux, this is not part of the standard and functions are not objects in C. However it usually works and since many people don't even know about these types I usually leave a comment explaining the trickery. Again, it is up to your implementation and not guaranteed anywhere in the language, but yes. @AnttiHaapala If I move a uintptr_t by 3, I'd also expect the corresponding char* to move by 3. IntPtr objects can also be used to hold handles. Hah, the Xor Linked List also is the reason why I can find this reason. Pointer/integer conversions simply copied the representation. Populates a SerializationInfo object with the data needed to serialize the current IntPtr object. That means that the memory address could be greater than 2^ (8 * 4)``. Pointers can only point to existent objects in the address space of the program itself, not some other process, and arithmetic on them is only valid as long as it stays within the object pointed into. Someone acratched their name and date on back and it says T. Edison 1906. @sleske that's not true. Converts the value of the specified IntPtr to a 64-bit signed integer. Formats the value of the current instance using the specified format. The Visual Basic example calls the Marshal.ReadByte(IntPtr, Int32) method to read the byte (or one-byte character) at a specified offset from the managed pointer to the ANSI string. Create an account to follow your favorite communities and start taking part in conversations. Computes the quotient and remainder of two values. But``int can only store adresses less than 2^ (8 * 4). Please review and enhance the photos as they are part of the description. Solution 1. int may not be large enough to store a pointer. Converts the string representation of a number to its signed native integer equivalent. Asking for help, clarification, or responding to other answers. MSDN Says: The IntPtr type is designed to be an integer whose size is platform-specific.That is, an instance of this type is expected to be 32-bits on 32-bit hardware and operating systems, and 64-bits on 64-bit hardware and operating systems.. So I should not assume those. What is the difference between char array and char pointer in C? If there is no integer type wide enough to hold a converted pointer value without loss of information, the implementation just won't define uintptr_t. In C99, it is defined as "an unsigned 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". 2) A pointer can be converted to any integral type large enough to hold all values of its type (e.g. int ptr_t thatvalue = 1 ; // stuff thatvalue = reinterpret_cast< int ptr_t> (ip); // Convert it as a bit pattern. Converts the numeric value of the current IntPtr object to its equivalent string representation. Converts the string representation of a number in a specified style and culture-specific format to its signed native integer equivalent. It is greatly appreciated. For more information, see nint and nuint types. Why should I use a pointer rather than the object itself? Since we install stripped binaries in APKs, print out object file names and relocatable addresses that can be used on the host machine to complete symbolizing and demangling the stack trace using unstripped binaries. The problem is a pointer to bytes is align 1 but a pointer to usize is align 8 (on 64 bit), zig will not let you cast any byte pointer to usize without an align cast which like you experienced will reject any that are not divisible by 8. as the control expression for an if, or as an operand to &&) is required to report any valid non-null pointer as true and any valid representation of a null pointer as false, regardless of the actual bit patterns used to represent such things. My code snippet looks like this: unsafe { char * a = null; IntPtr result = &a; } The second line is too obvious to fail. So if you are going to test address manipulation code you need a generalized object to do math on. Gets the largest possible value of IntPtr. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Subtracts an offset from a signed integer. It's an unsigned integer type exactly the size of a pointer. (Also wish enums where stronger typed but most debuggers do a good job of figuring them out any way). But I would like to know there is the (b) assertion came from? First, convert the pointer to uintptr_t. Because its starting value is the length of the string, the copy operation will copy a character from the start of the string to the end of the memory block. Vide: @sleske I wish that was available in C. But having stdint.h is better than nothing. It's also in C++11, in , where again it is optional, and which refers to C99 for the definition. On the other hand, programmers assume a pointer that's been ploughed with memset(, 0, ) will be set to NULL, so we are kind of hypocritical in this regard. To add to this, it is permitted for the implementation to have multiple representations of a null pointer, and it is entirely possible for these representations to yield different values when cast to uintptr_t. If 0x80 was not derived from a valid uint32_t *, the result in undefined behavior (UB). Making statements based on opinion; back them up with references or personal experience. Cast Grappling Hook @ Target location macro? How can i cast Value to a Pointer, so it points to 0x80? To learn more, see our tips on writing great answers. In .NET 7 and later versions, this type also implements the IBinaryInteger, IMinMaxValue, and ISignedNumber interfaces. In practice, it does exist. It could conceivably be smaller, although such a C++ implementation approaches perverse. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. Converts the value of this instance to a pointer to an unspecified type. The Visual Basic example uses this pointer directly; in the C++, F# and C# examples, it is cast to a pointer to a byte. Sed based on 2 words, then replace whole line with variable, Penrose diagram of hypothetical astrophysical white hole, Name of a play about the morality of prostitution (kind of). The method returns an IntPtr object that points to the beginning of the unmanaged block of memory. Is it a valid operation to cast a void* pointer to char* pointer and doing pointer arithmetics on it? Since pointers are all the samesize on a given platform - e.g. Tries to format the value of the current instance into the provided span of characters. However, there are specific cases when you may store a pointer in 32-bit types. It is not guaranteed to exist, but on platforms where it doesn't exist, what you're trying to do cannot safely be done without a great deal more information. The Unix-like OS needed to support 8-bit bytes, so byte pointers (void*, char*) contained a word address with a 3-bit offset stored in the otherwise unused high-order 3 bits of the 64-bit word. For example, instances of IntPtr are used extensively in the System.IO.FileStream class to hold file handles. How many transistors at minimum do you need to build a general-purpose computer? @PSkocik of course it doesn't hold, and it is not crazy at all. In C# starting from version 11 and when targeting the .NET 7 or later runtime, nint is an alias for IntPtr in the same way that int is an alias for Int32. Connect and share knowledge within a single location that is structured and easy to search. However, you can use a cast to convert a void pointer to any other pointer type, and vice versa. uint8_t* is a pointer (which has 4/8 bytes of size, depending on your architecture). Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. uintptr_t might be the same size as a void*. I've actually worked on systems (Cray vector machines) where arithmetic on uintptr_t wouldn't necessarily work. All the standard guarantees is that converting a. other than bit arithmetic it's also nice if you want to have semantics based on addresses instead of object counts. Gets the number of bytes that will be written as part of TryWriteLittleEndian(Span, Int32). uintptr_t is a data type that is capable of storing a pointer (also 4 or 8 bytes). These have various native bus width and the tensilica is actually a Harvard architecture with separate code and data buses that can be different widths. uintptr_t is an unsigned integer (at least) the size of a pointer. Better way to check if an element only exists in one array. CGAC2022 Day 10: Help Santa sort presents! That is, an instance of this type is expected to be 32 bits in a 32-bit process and 64 bits in a 64-bit process. Changing an array type 9. What is a smart pointer and when should I use one? uintptr_t is an integer type. A pointer can be null. What is the data type of pointer variables? unsigned integer type capable of holding a pointer to void. This is the gap that needs to be filled: Code: constexpr void doTheThing () { Foo foo; std::uintptr_t address = std::bit_cast< std::uintptr_t >( &foo ); T* bar = ? Memsize types in unions 8. The application is then forced to use the API to perform any operations on the object, @JoelCunningham: that works but isn't really any different from using, @CiroSantilli2016 A common use case is to pass just an int to an API which expects a void* to generic data. Solution. Not the answer you're looking for? (Edit: TIL C doesn't provide round-trip casting through integers, so no guarantees whatsoever.). The Visual Basic example uses this pointer directly; in the C++, F# and C# examples, it is cast to a pointer to a byte. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Thanks for contributing an answer to Stack Overflow! CGAC2022 Day 10: Help Santa sort presents! Implement basic stack traces on Android and reenable unit tests. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. This type is represented by the IntPtr type internally and provides operations and conversions that are appropriate for integer types. If the uintptr_t type exists, so does the intptr_t type. offsetof is useful for calculating an object pointer given a pointer to one of its members: You can do this in C++. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. When you convert a valid function (procedure) pointer, system pointer, invocation pointer, label pointer, or suspend pointer to a signed or unsigned integer type, the result is always zero. This is the type of thing anyopaque is for. This does lead to some computational effort in the CPU, to convert integers to floating point numbers, or the other way around: " (int) 12.345 " is the integer value 12 " (float) 12345 " is the floating point value 12345.0 Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. All pointers should be treated as opaque types, or in other words - their contents should not be your concern. In C# starting from version 9.0, you can use the built-in nint type to define native-sized integers. The compiler shows no warnings and the debugger tells me, that Pointer contains the correct address, Note: OP is doing half a "round-trip here. Parses a span of characters into a value. binder_uintptr_t is not the same as uintptr_t, so converting it into a pointer requires a second cast: drivers/android/binder.c: In function 'binder_translate_fd_array': Then convert the void * to the desired type. If you have a void* value and you want to add a byte offset to it, casting to char* is the correct approach. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. That's what it's for. intptr_t uintptr_t intptr_t uintptr_t intptr_t intptr_t uintptr_t intptr_t intptr_t int num; intptr_t *pi = # uintptr_t uintptr_t *pu = # Even with uintptr_t provided, casting pointers to integers isn't useful without also relying on implementation defined properties of the result. --> Not quite. Determines if a value represents an odd integral number. 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. It's in C99, in , as an optional type. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I've read a page describing null, and have some questions about it: Would void* null be casted to uintptr_t zero? We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. Code: Copy to clipboard uint8_t* charptr; uintptr_t var = reinterpret_cast<uintptr_t>(charptr); Isn't this simply working? Should I even consider using uintptr_t over char* in any case? This answer is maybe right for a different question, but completely wrong for OP's question. The Standard, however, doesn't recognize any concept of "portable to among all non-weird implementations", and would thus classify code requiring such behavior as "non-portable". The point is that shmat () returns a pointer. Received a 'behavior reminder' from manager. And the standard doesn't guarantee that uintptr_t exists. Cast int to pointer - why cast to long first? Function pointers are a separate matter. It then calls the Marshal.WriteByte(IntPtr, Int32, Byte) method to write the byte to the memory address defined by the starting address of the unmanaged block of memory plus offset. The C#, F# and C++ examples perform the copy operation, then decrement the pointer to the address of the next location in the unmanaged ANSI string and increment the pointer to the next address in the unmanaged block. Say, something like (uintptr_t)((void*)(NULL))==(uintptr_t)(0) or (void*)((uintptr_t)(0))==(void*)(NULL) but I'm not sure it would work. Don't use it in portable code. If you write ' (void *) -1' it's exactly the same, the integer -1 represented as pointer. In standard C, I don't know of any way to check the representation of null at compile-time. A common example is enforcing 16-byte aligned memory for certain video and performance critical applications. Converts the read-only span of characters representation of a number to its signed native integer equivalent. It then decrements offset. That being said, a lot of embedded code involves bit twiddling and address manipulations. @Konrad You could have posted the link. Most of my Intel machines are 64 bit. Tuesday, July 10, 2007 7:49 AM Answers 0 Sign in to vote IntPtr result = new IntPtr (a); (You don't need an '&' in front of the 'a' either) If not guaranteed by the standard, then how can these be checked in compile time? Any arithmetic operations on it are integer arithmetic, not pointer arithmetic. Creates an instance of the current type from a value, saturating any values that fall outside the representable range of the current type. Additional details on this type as well as other related types is available here: Thanks for the "". Is there a cast or function call in the std that would allow me to treat an address as an arbitrary pointer, T, inside a constexpr function? This also unifies the type between ARM EHABI and the other configurations, and allows getting rid of a number of casts in log messages. 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