No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. If the destination type is bool, this is a boolean conversion (see below). Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? The reinterpret_cast makes the int the size of a pointer and the warning will stop. There's probably little you can do except look or hope for a fixed 2.x version or upgrade to 3.x (I would assume it's 64-bit safe but this is just a guess, do research this issue before you upgrade). If the object expression refers or points to is actually a base class subobject of an object of type D, the result refers to the enclosing object of type D. Otherwise, the behavior is undefined: When the target type is bool (possibly cv-qualified), the result is false if the original value is zero and true for all other values. There is absolutely not gurantee that sizeof(int) <= sizeof(void*). The problem is not with casting, but with the target type loosing half of the pointer. On many systems, an 8-bit unsigned int can be stored at any address while an unsigned 32-bit int must be aligned on an address that is a multiple of 4. Do new devs get fired if they can't solve a certain bug? "-D_FILE_OFFSET_BITS=64" "-Wall" "-Winvalid-pch" "-g" "-Wthread-safety" "-Wno-microsoft-enum-forward-reference" "-Wno-unused-function" "-Wno-sometimes-unini You need to cast the void* pointer to a char* pointer - and then dereference that char* pointer to give you the char that it points to! The difference between a and &a is the type. By clicking Sign up for GitHub, you agree to our terms of service and Based on the design of this function, which modification is right. cast to 'double *' from smaller integer type 'unsigned int' The C compiler is gcc, clang version 3.9.1, target aarch64--linux-android, thread model posix. In my case, I was using a 32-bit value that needed to be passed to an OpenGL function as a void * representing an offset into a buffer. The value of float variable is= 37.75. I personally upvoted this answer because by it's first line of text it helped me to understand the reason of this strange error message and what am I, poor idiot, doing :D. Not valid on Windows 64 - long is still 32-bit but pointers are 64-bit. You use the address-of operator & to do that int x = 10; void *pointer = &x; And in the function you get the value of the pointer by using the dereference operator *: int y = * ( (int *) pointer); Share Improve this answer Follow edited Apr 15, 2013 at 13:58 answered Apr 15, 2013 at 13:53 Some programmer dude 394k 35 393 602 1 From that point on, you are dealing with 32 bits. What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. (int*)Pc = pa; After the execution of the above code all the three pointers, i.e., Pa, Pd, and Pc, point to the value 150. */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); for (i=0, j=0; j returnPtr[j] = (void *) (ptr + i); // <<< Compile Errors, Error1error C2036: 'void *' : unknown sizec:\temp\testone\lib\utils.c57, 2> returnPtr[j] = (void *) ((long*)ptr + i); // <<< No compile errors, 3> returnPtr[j] = (void *) ((char*)ptr + i); // <<< No compile errors. Not the answer you're looking for?
The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. "I think what you should do is actually pass the address of the variable to the function" Not necessarily. 7.1 New Cast Operations The C++ standard defines new cast operations that provide finer control than previous cast operations. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Mutually exclusive execution using std::atomic? -1, Uggh. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. If the sizes are different then endianess comes into play. You are correct, but cocos actually only uses that address as a unique id. You are just making it bigger by tricking the compiler and the ABI. I assumed that gcc makes a 65536 out of my define, but I was wrong. From the question I presume the OP does. You can fix this error by replacing this line of code. what does it mean to convert int to void* or vice versa? In the case of Widening Type Casting, the lower data type (having smaller size) is converted into the higher data type (having larger size). But the problem has still happened. It is purely a compile-time directive which instructs the compiler to treat expression as if it had . To learn more, see our tips on writing great answers. However, you are also casting the result of this operation to (void*). tialized" "-Wno-format" "-Wno-incompatible-pointer-types" "-Werror" "-dM" "-U_MSC_VER" "-D_TIMESPEC_DEFINED" "-D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_SECURE_NO_WA Just edited. Otherwise, if the original pointer value points to an object a, and there is an object b of the . And, most of these will not even work on gcc4. In such condition type conversion (type promotion) takes place to avoid loss of data. Implementation-dependent. Use returnPtr[j] = (void *) ((long)ptr + i); ). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. The most general answer is - in no way. lexborisov Modest Public. So the compiler is very picky here and the correct solution to make the code compile again and still let it show the exact same behavior like in Xcode 5.0 is to first cast to an integer type with a size that matches the one of a pointer and to then do a second cast to the int that we actually want: ids [i] = (int) (size_t)touch; Using Kolmogorov complexity to measure difficulty of problems? Are there tables of wastage rates for different fruit and veg? But assuming that it is, as long as the caller and the callee agree, you can do that sort of thing. (i.e. No idea how it amassed 27 upvotes?! Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. If this is the data to a thread procedure, then you quite commonly want to pass by value. For the second example you can make sure that sizeof(int) <= sizeof(void *) by using a static_assert -- this way at least you'll get a notice about it. "clang" "-Ilib\libopenvswitch.a.p" "-Ilib" "-I..\lib" "-I." I agree passing a dynamically allocated pointer is fine (and I think the best way). reinterpret_cast is a type of casting operator used in C++. You can use any other pointer, or you can use (size_t), which is 64 bits. And in this context, it is very very very common to see programmers lazily type cast the. rev2023.3.3.43278. This forum has migrated to Microsoft Q&A. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size);
The compiler issues the "cast from integer to pointer of different size" warning whenever the value of an integer is converted to a pointer, especially when the memory allocated to a pointer is smaller than the memory allocated to an integer data type. Your first example is risky because you have to be very careful about the object lifetimes. For example, the main thread could wait for all of the other threads to end before terminating. However the actual code in question contains an explicit c-style cast to int. ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Minimising the environmental effects of my dyson brain. *sound/soc/codecs/tlv320aic32x4.c:1202:18: warning: cast to smaller integer type 'enum aic32x4_type' from 'void *' @ 2022-04-22 9:48 kernel test robot 0 siblings, 0 . Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. If your standard library (even if it is not C99) happens to provide these types - use them. this question. The bigint data type is intended for use when integer values might exceed the range that is supported by the int data type.. bigint fits between smallmoney and int in the data type precedence chart.. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. A void pointer can be really useful if the programmer is not sure about the data type of data inputted by the end user. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Not the answer you're looking for? We have to pass address of the variable to the function because in function definition argument is pointer variable. How do I check if a string represents a number (float or int)? Whats the grammar of "For those whose stories they are"? /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Remarks. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Taking the above declarations of A, D, ch of the . Usually that means the pointer is allocated with. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. Using indicator constraint with two variables. Connect and share knowledge within a single location that is structured and easy to search. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. ../lib/odp-util.c:5665:7: note: expanded from macro 'SCAN_SINGLE' Find centralized, trusted content and collaborate around the technologies you use most. I'm trying to create a void* from an int. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. with ids being an array of ints and touch being a pointer. I guess the other important fact is that the cast operator has higher precedence that the multiplication operator. SCAN_SINGLE("skb_priority(", uint32_t, u32, OVS_KEY_ATTR_PRIORITY); Here, the Java first converts the int type data into the double type. Returns a value of type new-type. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. ^~~~~~~~~~~~~~~~~~~~~ pthread passes the argument as a void*. Any expression can be cast to type void (which means that the result of the expression is ignored), but it's not legal to cast an expression of type void to type int not least because the result of such a cast wouldn't make any sense. [] ExplanatioUnlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). What video game is Charlie playing in Poker Face S01E07? Identify those arcade games from a 1983 Brazilian music video, Relation between transaction data and transaction id, The difference between the phonemes /p/ and /b/ in Japanese. this way you won't get any warning. Typically, long or unsigned long is . It is done by the compiler on its own, without any external trigger from the user. What does it mean to convert int to void* or vice versa? Hence there is no loss in data. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Setting a buffer of char* with intermediate casting to int*. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Windows has 32 bit long only on 64 bit as well. The mapping in pointer<->integer casts is implementation defined, but the intent was that if the pointer type is large enough and isn't forcefully aligned (, But that's different. Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Acidity of alcohols and basicity of amines. Linear regulator thermal information missing in datasheet. windows meson: cast to smaller integer type 'unsigned long' from 'void *'. Note:You might receive a runtime exception if the pointer contains a value unsuitable for the context. (void *)i Error: cast to 'void *' from smaller integer type 'int' PS: UBUNTUCLANG3.5 clang -O0 -std=gnu11 -march=native -lm -lpthread pagerank.c -o pagerank c pthreads 4 10.3k 2 21 2015-06-05 It modifies >> Wconversion-real.c, Wconversion-real-integer.c and pr35635.c to be more >> specific > > If the patch passes existing tests, I'd be inclined to leave them > tests alone and add new ones that are specific to what this patch > changes. rev2023.3.3.43278. The best way is, if one can, do not do such casting, instead, if the same memory address has to be shared for pointer and int (e.g. How to use Slater Type Orbitals as a basis functions in matrix method correctly? Making statements based on opinion; back them up with references or personal experience. Here is my code: I already tried (void*)M_TABLE_SIZE but then I get an error that I cannot use the * operator. p-util.c.obj "-c" ../lib/odp-util.c If the original type is a void *, converting to an int may lose date on platforms where sizeof(void *) != sizeof(int) (which is true of LP64 programming model). error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. how to cascade 2d int array to 2d void pointer array? So,solution #3 works just fine. @Martin York: No, it doesn't depend on endiannness. this way I convert an int to a void* which is much better than converting a void* to an int. And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. The difference between the phonemes /p/ and /b/ in Japanese, Styling contours by colour and by line thickness in QGIS. In Java, there are two types of casting: Widening Casting (automatically) - converting a smaller type to a larger type size. If we want to get the exact value of 7/5 then we need explicit casting from int to float: Example: int x=7, y=5; For example, if youwrite ((int*)ptr + 1), it will add 4 bytes to the pointer, because "ints" are 4 bytes each. In simple example code like this it's very easy to convince yourself that there's no problem, but in more elaborate real-world scenarios it's very easy to make this mistake inadvertently. STR34-C. How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. @kshegunov said in Number Type Cast: const void * x; int y = int (x); compiles just fine. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Please note that the error I am receiving is "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha(residents[i].name) == 0). @LearnCocos2D: so, how can i "overcome" the error without editing any not-my-code or in-library-file lines? I recall there was a TreeNode(int) early on prior to 1.0 release I can't remember why I removed it, if I should felt it was easy enough to cast to (void*) or if it was because it created type inference conflict at the call site. But you seem to suggest by your answer that the user can pass 5 to pthread_create and then perform the above cast to get it back. So reinterpret_cast has casted it to long type and then static_cast safely casts long to int, if you are ready do truncte the data. This solution is in accordance with INT18-C. The main point is: a pointer has a platform dependent size. You use the address-of operator & to do that. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Yeah, the tutorial is doing it wrong. For a fairly recent compiler (that supports C99) you should not store or represent address as plain int value. itch" "-I..\include\windows" "-Iinclude" "-I..\include" "-I..\datapath-windows\include" "-IC:\PTHREADS-BUILT\include" "-Xclang" "-fcolor-diagnostics" "-pipe" and how to print the thread id of 2d array argument? There are ways to prevent this: pass a dynamic allocated argument if your not the passing thread is not static or if your argument is a local variable, otherwise there is no issue. ../lib/odp-util.c:5834:5: error: cast to smaller integer type 'unsigned long' from 'void *' [-Werror,-Wvoid-pointer-to-int-cast] Making statements based on opinion; back them up with references or personal experience. Infact I know several systems where that does not hold. Casting an open pointer to other pointer types and casting other pointer types to an open pointer does not result in a compile time error. Is it possible to create a concave light? How do I count the number of sentences in C using ". The preprocesor absolutely will not perform arithmetic. Find centralized, trusted content and collaborate around the technologies you use most. @Shahbaz you could but I will not suggest to a C newbie to use globals. I'm unfamiliar with XCode, but the solution should be something like follows: Most of the "solutions" above can lose part of the pointer address when casting to a smaller type. Whats the grammar of "For those whose stories they are"? ^~~~~~~~~~~~~~~~~~~ /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. Well it does this because you are converting a 64 bits pointer to an 32 bits integer so you loose information.
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