When length is zero, it is probably unusable condition for this function. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Aaron:I suspect we are talking past each other. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. Asking for help, clarification, or responding to other answers. Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. Why pointers are not used in python? Explained by Sharing Culture Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? Because a null pointer does not point to a meaningful object, an attempt to dereference(i.e., access the data stored at that memory location) a null pointer usually (but not always) causes a run-time error or immediate program crash. Is it possible to rotate a window 90 degrees if it has the same length and width? It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); rev2023.3.3.43278. The problem is, I hope this code's result to be <5,3> and <9,6> BUT the console only shows me <5,3> and <9,3>. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. . We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. Shouldn't the function check all pointers before dereferencing them or passing them to another function? 4. But even with this, the concerned object it tagged as a possible NullPointerException problem. What is generic pointer? False fault 'Null pointers should not be dereferenced' using Optional @Tibor SonarQube version 5.6.6, IntelliJ SonarLint plugin 3.0.0.2041, Sonar: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. Recovering from a blunder I made while emailing a professor. A value is checked here to see whether it is null, but this value can't be null because it was previously dereferenced and if it were null a null pointer exception would have occurred at the earlier dereference. Why does the second compliant example permit using possibly-null pointers? Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Null Pointer 1 Answer Sorted by: 1 Your code is ok. int changed to size_t and if size_t parameter's is zero, allocate one word. A nonnegative return value represents the number of bytes successfully read (the return value is a "signed size" type, usually the native integer type for the target platform). FindBugs CORRECTNESS - (C11, S7.24.2.1). In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. Isn't easier just to check valid range of length? For the time being, I would unfortunately recommend to mark as False Positive the issue. SonarQube null pointers should not be dereferenced on try/catch, Sonarcube :Null pointers should not be dereferenced, How do you get out of a corner when plotting yourself into a corner. We might set a pointer to null even if we are not freeing a object, simply to dissociate one object from another: tty_driver->tty = NULL; /* detach low level driver from the tty device */ 0 is certainly within the 'domain of the function' (a phrase defined by mathematics but not by C11), as copying 0 bytes is well-understood (although silly). Using Kolmogorov complexity to measure difficulty of problems? That interpretation of the standard is not supported universally. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. Why does Mister Mxyzptlk need to have a weakness in the comics? On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. Software project. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Im having trouble understanding your problem. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. String *x, y; X is a pointer to a string, Y is a string & = address of variable/ operator || referencing operator * = value of address || dereferencing operator Pointers = stores memory address as its variables NULL pointer = a constant with a value of zero defined || assigned to null Void pointer = a pointer that is not associated with any data types New operator = denotes a request for . The 4gig boundary will probably be important too with unsigned int in LP64, but since size_t will be 64-bit, there will have to be some truncation that compilers will be able to warn on. . If the pointer is not NULL, see if the assignment occurs only in a branch of a conditional statement.Investigate when that branch does not execute. So let me be more precise in my wording: I assert that a platform whose memcpy() did anything besides copy zero bytes when given n=0 and valid src and dest pointers was not C-standards-compliant. Best to cite C11 s7.24.2.1 here: The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. Thanks for contributing an answer to Stack Overflow! Automated Detection Null pointer dereferences can happen in path-dependent ways. Trying to understand how to get this basic Fourier Series. IDE extension that lets you fix coding issues before they exist! You do not have permission to delete messages in this group, Either email addresses are anonymous for this group or you need the view member email addresses permission to view the original message. SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. Because null pointer dereferencing is UB, the if (!tun) check can be elided entirely by the optimizer (since the tun->sk implies that tun must be non-null). Powered by Discourse, best viewed with JavaScript enabled. How can we prove that the supernatural or paranormal doesn't exist? In the meantime, Im locking this thread. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. Software project. The above check can't hurt, as I guess you could have a system with a 32-bit size_t that had a ton of memory and had some crazy banking/selector scheme with pointers. This rule applies to all null pointers, regardless of which function returned them. Null Pointer Exception In Java - GeeksforGeeks - A computer science Because null pointer dereferencing is undefined behavior, the compiler (GCC in this case) can optimize away the if (!tun) check because it is performed after tun->sk is accessed, implying that tun is non-null. SonarJava Version 5.9.2 (build 16552). Thus we should check > this kstrdup() operation. Explain about call by reference with an . Find centralized, trusted content and collaborate around the technologies you use most. Solution 1, it looks like, today's solution tomorrow's problem. By 'valid pointers' I mean that both src and dest pointers are not null and they both point to non-overlapping arrays containing at least n bytes each. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). You can use Optional instead. However there is no portable way to verify that the pointer is valid, other than checking for null. Asking for help, clarification, or responding to other answers. , RemoteContext new ExceptionType() RemoteContext , SonarLintJava (), java - sonarLint "Null pointers should not be dereferenced (squid:S2259)"Stack Overflow Batch split images vertically in half, sequentially numbering the output files, Difficulties with estimation of epsilon-delta limit proof, Minimising the environmental effects of my dyson brain. sonar-java. This code also violates ERR33-C. Detect and handle standard library errors. Asking for help, clarification, or responding to other answers. Passing ownership of something also requires pointers. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? To learn more, see our tips on writing great answers. Hello. We can not disable any rule, sonar do validation in "Sonar way" (actual name of profile :) ), so we will need to mark them "Wont fix" each time it appear again in new code. Void pointers cannot be dereferenced as any other pointer. Sonar is ok. Sonar can't determine that the helper method did the null validation. Null pointer should not be dereferenced , versions used (SonarQube, Scanner, language analyzer) 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. To learn more, see our tips on writing great answers. Dereferencing a null pointer is undefined behavior, typically abnormal program termination. Does Counterspell prevent from any further spells being cast on a given turn? I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. The n=0 is a mildly interesting edge case: Clearly a pointer that points to at least one valid byte could be used as the src or dest pointer to a call to memcpy(, 0). [SONARJAVA-2808] - Jira - SonarSource Handling Java NullPointerException and Best Practices - HowToDoInJava This solution also ensures that theuser_data pointer is not null. But when length of A is 1, the control never reaches the else block. The approximation of the try catch flow is such that we consider an exception can be thrown just after the curly brace of the try. Phew, we're agreed here. Coverity Prevent cannot discover all violations of this rule, so further verification is necessary, Detects when NULL is dereferenced (Array of pointers is not checked. How do I align things in the following tabular environment? In C, dereferencing a null pointer is undefined behavior. Since you cannot have a variable of type void, the pointer will not point to any data and therefore cannot be dereferenced. (from res.getBody().getServiceResult() ). In the simplest case, this function just returns the result of calling kmalloc. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. NullPointerException is a RuntimeException. In order to fix this, just do the following: If you are absolutely sure that res.getBody() stays null and is also not modified by another thread, you could also use a //NOSONAR comment in order to suppress the warning. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Pointer members in structs are not checked. the Java one). The SonarJava SE engine is however, by default, not configured to explore methods declared in other files (in your case, your utility class CheckUtils). The same problem we will have with "Add at least one assertion to this test case." Connect and share knowledge within a single location that is structured and easy to search. Thanks, David! 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. A reference to Nothing should never be dereferenced/accessed. () These can be: Invoking a method from a null object. If that variable hasn't had a reference assigned, it's a null reference, which (for internal/historical reasons) is referred to as a null pointer. All rights are expressly reserved. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Not the answer you're looking for? Haiku is a free and open-source operating system for PC designed to be binary compatible with the BeOS operating system and embodying the basic ideas of BeOS. Unfortunately the problem is much more complex, and generally unsolvable within standard C. Consider the following example: There's no way f can check whether x points into valid memory or not. SonarQube - Null Pointer Dereference Issue - Sonar Community I already tried to put ResponseEntity responseDto inside my try clause assigning and returning the respective value but its mandatory to return something out the try/catch. minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). In Java, a special null value can be assigned to an object reference. parsing /proc/self/maps under linux) one might find out whether the pointer points into mapped memory, but this is still not a guarantee of validity because it is very coarse-grained see again the above example. which would allow us to systematically observe what you are having. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. CWE - CWE-476: NULL Pointer Dereference (4.10) - Mitre Corporation The Clang Static Analyzer already has a checker to find the null pointer dereference in code, however it is not sufficient for higher abstractions such as C++ smart pointers or optionals. So Bar might not be initialized but then the last line of your example should not be evaluated in this case. A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. A reference to null should never be dereferenced/accessed. So we have to check all the arguments before performing any actions. While the engine is in practice already able to explore code from other files if needed (relying solely on bytecode), we restrain this approach to a limited set of well-known methods from standard libraries, for which we know that behaviors are correctly produced. context.RaiseException , (/) that we haven't considered here: I'd guess null pointers are not valid, even though they point to 0 bytes. Pointer is so confusing : Stack with singly linked list in C - Stack (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) There is no legitimate reason to dereference a null pointer unless you on a rare system that maps page zero (or you intend your program to crash). Making statements based on opinion; back them up with references or personal experience. 1 Answer Sorted by: 2 Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. The purpose of a NULL pointer is not to cause a processor exception when it is dereferenced (although that is nice to have for debugging.) It is still a pointer though, to use it you just have to cast it to another kind of pointer first. How to deal with "java.lang.OutOfMemoryError: Java heap space" error? io.NotSerializableException : java. We really appreciate your help. how to handle Sonarlint java:S2259 (Null pointers should not be How do I align things in the following tabular environment? Finally my method is returning a response with value of restTemplate. It also reinforces the notion to the reader that any time you see arithmetic in an allocation expression, you need to think about corner-cases. CWE-476: NULL Pointer Dereference: A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. {"serverDuration": 214, "requestCorrelationId": "084acdc104f21c51"}, EXP34-C. Do not dereference null pointers, Clever Attack Exploits Fully-Patched Linux Kernel, ERR33-C. Detect and handle standard library errors, one compliant and one non-compliant example, CERT Oracle Secure Coding Standard for Java, EXP01-J. I say "theoretical" because I have not successfully produced strings of this length in testing. Is the God of a monotheism necessarily omnipotent? . Issues Components. The null pointer check for writing or dereferencing should be a compiler flag or library setting. Making statements based on opinion; back them up with references or personal experience. After that, you call res.getBody() again. There can be a null pointer type for each pointer type, such as a pointer to a character or a pointer to an integer, although this is . EXP01-J. Do not use a null in a case where an object is required SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! Sonar violation: Null pointers should not be dereferenced #7459 - GitHub A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? If copying takes place between objects that overlap, the behavior is undefined. Dereferencing > this null pointer may cause the kernel go wrong. What is null pointer exception in android Smartadm.ru Do not use a null in a case where an object is required, https://gcc.gnu.org/gcc-4.9/porting_to.html, Prior to 2018-01-12: CERT: Unspecified Relationship, Pointer Casting and Pointer Type Changes [HFC], Dereferencing an out-of-domain pointer [nullref], Section 5.2.18, "Null-Pointer Dereference", Dereferencing null pointers that were not returned by a function. References, C++ FAQ How to tell which packages are held back due to phased updates. Just a few words about the rule now. The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. How do you ensure that a red herring doesn't violate Chekhov's gun? ROSE does not handle cases where an allocation is assigned to an lvalue that is not a variable (such as a struct member or C++ function call returning a reference), Finds instances where a pointer is checked against NULL and then later dereferenced, Identifies functions that can return a null pointer but are not checked, Identifies code that dereferences a pointer and then checks the pointer against NULL, Can find the instances where NULL is explicitly dereferenced or a pointer is checked againstNULL but then dereferenced anyway. Null pointers should not be dereferenced #1155 - GitHub Unfortunately, its actual state also has some limitations, like the one you are hitting here. (in the meantime, in case of any other false-positive suspicion, make sure to check those latest versions as bunch of improvements are regularly released). Rule squid:S2259 is based on a Symbolic Execution (SE) engine. Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. How to avoid dereferencing null pointers in Java - Quora A null pointer stores a defined value, but one that is defined by the environment to not be a valid address for any member or object. Doing so will at best cause abrupt program termination, without the All content is copyright protected. Iflengthhas the value1, the addition yields 0, and png_malloc() subsequently returns a null pointer, which is assigned to chunkdata. [JAVA] 3.9 - FP for S2259 Null pointers should not be dereferenced I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. Correct; a null pointer is not a valid pointer for the C library functions. When a variable is declared as being a pointer to type void, it is known as a generic pointer. Sonar false-positive on rule: Null pointers should not be dereferenced Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. IMHO, the rule title should be changed to something less general. (I think you cover that in a different rule.) uninitialized reference-type class members. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. A null pointer in this position causes the read system call to fail with -EINVAL ("Invalid argument"). All content is copyright protected. S2259: Null pointers should not be dereferenced - Sonar Community By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Things go fine now. We have a false positive with the " Null pointers should not be dereferenced -squid:S2259" rule : We have a "NullPointerException" false positive for which we do not know how to solve it. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. isEmpty(Map map) So the first execution of ValidateNumber inside the foreach works fine and valid is set to true.The second execution throws the exception and exception is set in the catch-Block.. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. Calls to extension methods are not reported because they can still operate on null values. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Good question! Doing so will cause a NullReferenceException to be thrown. The result of calling such a helper function should be . False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. When and how should I use a ThreadLocal variable? Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. SonarLint IntelliJ 4.0.0.2916 Java Rule 'Null pointers should not be dereferenced' I'm getting this fault in the next code when obj can't be null in any scenario. What is a NullPointerException, and how do I fix it? Do not dereference null pointers Created by Jeffrey Gennari, last modified by Jill Britton on Jan 18, 2023 Dereferencing a null pointer is undefined behavior. So you can declare a string t and then add characters to the string with a plus sign : t += 'a'; The code you are having issue with is just moving the pointer to the next character which the foreach is already doing. And the semantics, as I said, are different. On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. Not the answer you're looking for? But when length of A is 1, the control never reaches the else block. Avoid Returning null from Methods. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Whats the grammar of "For those whose stories they are"? The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. Likewise, pointers to freed memory are not valid. Thanks for contributing an answer to Stack Overflow! assert(!invalid(p)); // or whatever, bool invalid(const void *p) { What is null pointer exception in android. If you preorder a special airline meal (e.g. I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. A reference to null should never be dereferenced/accessed. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). As for today, the SE engine is able to explore non-overridable methods (static, for instance), when declared in the same file being analyzed. In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. Asking for help, clarification, or responding to other answers. very old code or C code being worked into c++ may have functions that expect the user to delete the data. Find centralized, trusted content and collaborate around the technologies you use most. Discover SonarLint SaaS Setup is effortless and analysis is automatic for most languages Discover SonarCloud Self-Hosted Fast, accurate analysis; enterprise scalability Discover SonarQube Secrets ABAP Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. This topic was automatically closed 7 days after the last reply. I guess you could write a proposal to modify the C Standard, but our coding standard is meant to provide guidance for the existing language. It's even called out explicitly in C17 7.24.1p2: Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. That's true. Also, the term 'pointer' is bad (but maybe it comes from the FindBugs tool): Java doesn't have pointers, it has references.
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