Not returning a value from a non-void function is illegal. See for more on error handling. Simplest thing to do would be to actually write the function at this point. It hath been already of old time, which was before us. Quote: apart from the warning? "return 1;" terminates the loop and the function without "incrementing". Have a question about this project? -- I am spammed, therefore I am. I am having a slight is regarding functions. Missing it seems odd to me, but I'm not an optimizer. Add a return 0; at the end of your method. Generally, we ignore this error because most of the time as the program still runs the same even if this warning is coming. Run-time error: Error which occurs when the program syntax is correct but there is some problem while the program is run. Your compiler is trying to communicate! You need to write something in the code for shift that will return an int. If that's how you intended the function to work because you guaranteed by design that not returning a value will not cause a problem, you can turn off that warning. Many compilers will generate code for the checkpass function, returning various values along the execution path where no return statement is defined. Assumably, it means that you have to return a value using the return statement before the end of your function. Too bad one can't put attribute unroll on a for loop. To overcome this error or the representation of the code is to flow the pseudocode. Apologies for the poor formatting of my question but this is my first time here and I was hoping to be able to do it alone. output both infix and RPN strings into output file. Now coming to the runtime and compile-time error part, the message which we are getting here is identified at compile time using just the syntax of the program and the program is not actually run to check if it is reaching the end of any non-void function. I recently started thinking about a , and I would like to know the setups where these issues occur typically. Otherwise you may miss the fact that you forgot to put a return statement at the end of one of your functions. As you said, sometimes severely nested code leads to. else construct at a time, so the last else block is attached only to the outer if conditions and not to the inner if conditions. Threads are not part of the C standard, so we avoid talking about them in comp. use stack to convert input string into RPN output string 4. I did everything according to the tutorial but the clang keeps showing an error: "control reaches end of non-void function" on the very last line. Cliff wrote: If you later decide to add something that must be done before return like deselecting an SPI device say then having just one point of exit means you need only do it in one place - rather tha[n] duplicating it at several points. I was a bit stuck because of this. The best method for handling this type of error is specific to the application and the type of error. Because control reaches the end of a function that returns a ptr-to-void and yet you don't return anything. Here's a representation of that control flow in pseudocode: if outer-condition-1 if inner-condition-1 return 1 else if outer-condition-2 if inner-condition-2 return -1 else return 0 An else block is only ever related to one if. It means you have a function that's supposed to return some type of value, and there is a way for the processor to "fall off" the end of the function without executing a return statement. Placing a return inside a block intends to avoid any action represented by the rest of the block, including the implied actions at the closing bracket, e. Compliant Solution This compliant solution changes the interface of getlen to store the result in a user-provided pointer and returns a status indicator to report success or failure. Often when we run into the warning saying warning: control reaches end of non-void function. I got this warning message "warning: control reaches end of non-void function" May I know exactly what does it mean? Noncompliant Code Example In this noncompliant code example, control reaches the end of the checkpass function when the two strings passed to strcmp are not equal, resulting in undefined behavior. Neither warning is required; it's up to the whim of the compiler writer to decide what warnings to issue as long as it emits any diagnostics required by the standard. It's basically a failsafe, if none of the if conditions are met. Asking for help, clarification, or responding to other answers. c:12: warning: control reaches end of non-void function None of the inputs to the function equal the delimiter, so when run with GCC 5. Hi, i'm working on an infix to RPN program for my CS2 class. Quote: Exit paths from both block types[. However I would suggest you at least return zero instead of just turning off the warning. Control in the warning message means the flow of the program. There is an easy solution to the problem, even if we understand that every condition is covered we should add a return statement at the end of the function so the compiler is sure that the non-void function will be returning some value. At least that is as far as I can tell from your partial code. Optimization turned off probably is. Sorry Cliff, it was a misunderstanding then. And you call push repeatedly on the same char. Every function has a return type which states the type of value the function will be returning. However, for this, the function requires a return value. main function to call createStack and readEm functions. In article , Thomas Barth wrote: could someone explain to me why the compiler outputs a warning that the control reaches the end of a non void function? The two solutions are either to cover every potential return path with a return that provides a value - so in this case add a dummy "return N;" beyond the atomic block or to follow my advice. -- Is there any thing whereof it may be said, See, this is new? Would you please share the relevant snippets for further discussion? A related concept is "single entry, single exit" SESE , which would demand that your function return a value only once at the end, rather than using the "early return" statements inside the conditional logic. That's the effect, but surely not the intention? Personally I don't like functions with multiple exit points unless it's totally unavoidable like heavily nested error escapes. Don't expect more; always expect less. any help would be appreciated if. "Control reaches end of non-void function" means your function has a path through it where the function ends without actually returning data of the type declared in the function declaration. There are two important kinds of error which occurs while running a program. Hello everyone, In this article, we are going to discuss a common problem faced by beginners and also experienced programmers. personal goal keep main function as clean and short as possible. c so I can just call it later in the main search function. thanks for any help you can give. I've been getting strange compiler errors on this binary search algorithm. Because the potentially undefined return value of getlen is later used as an index into an array, a buffer overflow may occur. However do follow the advice someone gave above and check your optimisation. Another way is to flatten your nested conditions, so that the pseudocode looks like this: if outer-condition-1 and inner-condition-1 return 1 else if outer-condition-2 and inner-condition-2 return -1 else return 0 That might be appropriate if you're sure your program is working as intended with the current setup. The most direct solution is to add a return statement at the end of the function, outside of the conditional statements, but that's a bit messy, it can hide problems that would otherwise throw errors, making it a bit harder to find bugs. I thought your "you don't want" was meant as "it won't work anyway". In this case, there are two initializations, for i and n. Working on pset3 and tried to write a separate binary search function in helpers. With a switch-case tree, you can very easily add new sections and rearrange their order in a UITableView. We get the above error when the non-void function is not returning any value. I believe it is likely because I am not using them. In most of the simple cases for which it was intended it appears to work as advertised. Generally, these are syntax error which is identified without running the program. It may happen that flow is never reaching that part of the code but it is important to write for the compiler. create function to determine priority of the operators. To understand this error we first have to understand the working of the compiler a bit in detail. Which then leads us to the "goto" rat hole of a discussion. This warning is similar to the warning described in return with no value. Is the binary search itself broken or am I calling it wrong in search? If an outer condition evaluates to true and its inner condition evaluates to false, the else block will not be executed at all. Don't put kludge on kludge, don't mess with the mess. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. 3 on Linux, control reaches the end of the getlen function, which is undefined behavior and in this test returns 3, causing an out-of-bounds write to the data array. The warning is clearly superfluous. if outer-condition-1 if inner-condition-1 return 1 else return 2 else if outer-condition-2 if inner-condition-2 return -1 else return -2 else return 0 In either case, once the program reaches the first if statement, every path available to it will result in an explicit return statement, thus avoiding the control my reach end of non-void function. " As a result , it is permissible for control to reach the end of the main function without executing a return statement. c:70:1: warning: control reaches end of non-void function [-Wreturn-type] Is there a simple fix for this or do I have to write my program to use functions propely? Also please accept one of our answers : — Nov 17 '16 at 22:07. Did you mean it to be void callOp void? " isn't standing in for any statements that can alter control flow. The warning in question is -Wreturn-type, so to specifically disable that warning you would add -Wno-return-type to the build settings for the Makefile. Insert any int you like in place of "12345" above - that return statement will never be reached anyway. Since it has no return statement in fact, no code at all , it isn't returning an int, so the compiler throws an error. The code becomes trivially easy to read by using sensible naming conventions. But that's the very reason the OP started this thread. In the example given, the warning is clearly superfluous. It may be true that it's impossible due to external logic for priority 'a' to be called, but all the compiler sees is that there is a function where not all code paths return a value. If you want to make sure one of the conditions is met, return -1; should cause the application to throw an exception and crash, which might help you track down errors. exe without fixing it i get a infinite loop telling me the stack is full, which i am sure means something but i dont know what. Within each section, there can be multiple parts. If this answers your question, please click on the check mark to accept. Each section is separated by semicolons. But avoid …• Now that you have your errors sorted out, you're back to figuring out how to make it work. Debugging a binary search function is tedious though, so I recommend paying close attention to the spec and also look up some resources; I'd start with and then I also found an interesting article on the topic , skip over any code you see though, as implementing binary search yourself is half the fun! At the end of the function, add a return statement that returns a suitable return value, even if control never reaches there. I am unable to change how I compile the code as it has to follow a set spec. In this case, your shift function is declared to return an int. Therefore the code that calls this function is expecting a return value, but it's possible the function will not return one and that's why you get the warning. I get a warning that control reaches end of non-void function. Provide details and share your research! I'm not sure, but you never call pop anywhere. You might also look at modifying this method and replacing the if statements with a switch-case tree. If you want the warning to go away, the easiest thing would be to add a default: option to your switch statement, and return some dummy value or perhaps throw an exception. I would think that the warning is completely clear. Thanks for contributing an answer to Stack Overflow! Though this certainly could be seen, I would not think it unusual that the optimizer would miss an optimization that relies on several conditions. ] What part of that is ambiguous? Telegram-cli uses libtgl version 2. Please be sure to answer the question. This does not apply to void functions because a void function does not return a value. I have just do it for my own code and it works. But if you need something unique to happen when an outer condition is satisfied and an inner condition is not satisfied, you need to keep the nested structure but deal directly with every possible outcome. exe without fixing it i get a infinite loop telling me the stack is full, I didn't run your code, but it looks like your while loop on line 127 is looping while NOT empty stack. They are separated by the comma. Those parts are separated by commas. Quote: I only have one exit path If you have a return in the middle of an atomic block, then you most certainly don't have only one exit path, at least as far as the compiler is concerned. If the function is not going to return any value it is given a void return type, Any other return valued function is a non-void function. This means the function will never encounter an explicit return statement, which is what the compiler doesn't like; every function must always return something, no matter what input it receives. Memloop's example has only one exit path. It's really easy; Fraser Speirs has a. Quote: Too bad one can't put attribute unroll on a for loop. Let's keep up on forum maintenance. If you later decide to add something that must be done before return like deselecting an SPI device say then having just one point of exit means you need only do it in one place - rather that duplicating it at several points. Control never reaches the end of the function, ergo. dat" ; ofstream outf "Program3RPN. Firsty, I use a comma and then two semicolons. There are a few ways to fix this. Compile-time error: Error which can be identified by the compiler without running the program. My suspicion is that the OP has optimization turned off and that the compiler never realizes that the for loop will never complete. Sometimes it may be the case that we have several if-else if statements with return value which cover all the conditions but if there is no else statement we will still get the error because the compiler could not understand that all the conditions are covered. Hi could someone explain to me why the compiler outputs a warning that the control reaches the end of a non void function? I'm sure there are still a few things that need to be worked out in my main while loop, but i can't see the problem in my out put because i get a "warning: control reaches end of non-void function [-Wreturn-type]" about my int priority function and i dont really understand what it means. If control reaches the end of a function and no return is encountered, GCC compiler assumes a return with no return value. Making statements based on opinion; back them up with references or personal experience. Generally invalid memory access, infinite loops fall under runtime error. output infix and RPN strings to Program3RPN. convert infix expression to RPN. include parentheses in conversion, and add extra date to input file to be read in.。 。 。
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