Compile Time Error In C
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used is not recognised by the compiler. This is usually because the programmer has either made a simple typing slip, or because example of compile time error in c he or she has not completely understood the rules of the language
Compile Time Error In C Programming
as they apply to the programming construct. In some sense, compile time errors are the easiest to correct, compile time error and run time error because they always result in an error message. Unless the error is so severe that the compiler cannot continue, the translation process will continue with the possibility of detecting compile-time error vs runtime error in c further errors. It is possible that the errors detected are not ``genuine'' errors, but consequences of earlier errors. A simple example of this is the problems caused if there is an error in the declaration of a variable. The compiler will not recognise the variable as such when it is used, and it will complain about `` Undeclared variable''. In
Compile Time Error And Runtime Error In Java
order to recover from this, many compilers make some assumption about the variable and continue, so that other errors can be found. Typically this will involve assuming that the variable has been declared of type int, and continuing. This assumption may itself cause further compilation errors if an int variable is not acceptable. A common cause of apparently correct programs causing compilation errors is a comment which is not terminated correctly. Apart from the // comment which terminates at the end of the line, C++ supports a comment that starts with /* and extends until a matching */ character pair. Omitting the closing */ causes havoc! Similar problems occur with missing quotation marks on strings " or characters '. Typing errors in variable identifiers and keywords can be difficult to spot: watch out for confusion between the letter l (el) and the digit 1 (one). Other characters that often cause errors, particularly when transcribed from handwritten notes are z and 2, s and 5, and o and 0. The compiler also distinguishes between upper and lowe
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Compile Time Error And Runtime Error In C
million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Runtime vs Compile time up vote 179 down vote favorite 171 Can anyone please give me a good understanding of https://www.macs.hw.ac.uk/~pjbk/pathways/cpp2/node123.html whats the difference between run-time and compile-time? compiler-construction runtime compile-time share|improve this question edited Oct 31 '09 at 13:35 e-satis 250k82236286 asked May 10 '09 at 21:06 devforall 1,807112641 add a comment| 19 Answers 19 active oldest votes up vote 253 down vote accepted The difference between compile time and run time is an example of what pointy-headed theorists call the phase distinction. It is one of the hardest concepts to learn, especially http://stackoverflow.com/questions/846103/runtime-vs-compile-time for people without much background in programming languages. To approach this problem, I find it helpful to ask What invariants does the program satisfy? What can go wrong in this phase? If the phase succeeds, what are the postconditions (what do we know)? What are the inputs and outputs, if any? Compile time The program need not satisfy any invariants. In fact, it needn't be a well-formed program at all. You could feed this HTML to the compiler and watch it barf... What can go wrong at compile time: Syntax errors Typechecking errors (Rarely) compiler crashes If the compiler succeeds, what do we know? The program was well formed---a meaningful program in whatever language. It's possible to start running the program. (The program might fail immediately, but at least we can try.) What are the inputs and outputs? Input was the program being compiled, plus any header files, interfaces, libraries, or other voodoo that it needed to import in order to get compiled. Output is hopefully assembly code or relocatable object code or even an executable program. Or if something goes wrong, output is a bunch of error messages. Run time We know nothing about the program's invariants---they are whatever the programmer put in. Run-time invariants are rarely enforced by the compiler alone; it needs help
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Fatal Errors Logic Errors Note that the error messages shown below may be specific to our compiler/linker or machines. Nonetheless, other systems and compilers will provide similar information. Compiler Messages When the compiler is compiling your code (i.e., converting your code into instructions the machine understands), it will report problems that it finds in your code. Aside: Here, we are being technical and refer to compiling as the stage before linking. Linking is when all the compiled pieces of a program and the libraries it uses (e.g., for cin) are put together to form an executable. Often, compiling and linking together are just referred to as compiling. There are two severities of messages the compiler can give: Compiler Warnings A compiler warning indicates you've done something bad, but not something that will prevent the code from being compiled. You should fix whatever causes warnings since they often lead to other problems that will not be so easy to find. Example: Your code calls the pow() (raise to a power) library function, but you forgot to include math.h. Because you've supplied no prototype for the pow() function (its in math.h), the compiler warns you that it assumes pow() returns an int and that it assumes nothing about pow()'s parameters: somefile.cpp:6: warning: implicit declaration of function `int pow(...)' This is a problem since pow() actually returns a double. In addition, the compiler can't type-check (and possibly convert) values passed to pow() if it doesn't know how many and what type those parameters are supposed to be. Note: The compiler will label warnings with the word warning so that you can distinguish them from errors. Compiler Errors A compiler error indicates something that must be fixed before the code can be compiled. Example: You forget a semi-colon (;) at the end of a statement and the compiler reports: somefile.cpp:24: parse error before `something' Always remember to fix the first few errors