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1. Top results related to what are the function of dictionary in c compiler

   • What are the benefits of function pointers in C?

     Top Answer

     Answered Jul 19, 2017 · 3 votes

     • Same as regular typdefs, incredibly useful for 2 and 4. Instead of typing the whole thing, you can now use myFuncDef
     • A function declaration for a function that recieves a function pointer. A function that takes a function pointer of 1. would thus look int add2to3(myFuncDef functionPtr);
     • -
     • A function that takes an int and (probably based on that) returns you a function pointer. Using the typedef it would have looked like myFuncDef functionFactory(int n);

     Without typedefs these chains of pointers to pointers could get incredibly long as can be seen in this question: C syntax for functions returning function pointers

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   • What are the semantics of function pointers with empty parentheses in each C standard?

     Top Answer

     Answered Mar 25, 2018 · 2 votes

     N1570 6.11.6:

     The use of function declarators with empty parentheses (not prototype-format parameter type declarators) is an obsolescent feature.

     This same wording appears in the 1990, 1999, and 2011 editions of the ISO C standard. There has been no change. The word obsolescent says that the feature may be removed in a future edition of the Standard, but so far the committee has not done so. (Function pointer declarations are just one of several contexts where function declarators can appear.)

     The Introduction section of the C standard explains what obsolescent means:

     Certain features are obsolescent, which means that they may be considered for withdrawal in future revisions of this International Standard. They are retained because of their widespread use, but their use in new implementations (for implementation features) or new programs (for language [6.11] or library features [7.31]) is discouraged.

     A call to a function declared with an old-style declarator is still required to pass the correct number and type(s) of arguments (after promotion) as defined by the function's actual definition. A call with incorrect arguments has undefined behavior, which means that the compiler is not required to diagnose the error; the burden is entirely on the programmer.

     This is why prototypes were introduced, so that the compiler could check correctness of arguments.

     On an i386 system with GCC, “extra” arguments passed in a call to an empty-parentheses-type’d function pointer are ignored, because of how stack frames work ...

     Yes, that's well within the bounds of undefined behavior. The worst symptom of undefined behavior is having the program work exactly as you expect it to. It means that you have a bug that hasn't exhibited itself yet, and it will be difficult to track it down.

     You should not depend on that unless you have a very good reason to do so.

     If you change

     int (*fp)() = foo;-

     to

     int (*fp)(int) = foo;-

     the compiler will diagnose the incorrect call.

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     2/5

   • What are the different between calling constructor and calling function pointer of constructor in C++

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     Answered Jan 28, 2024 · 0 votes

     Calling a constructor and calling a function pointer of a constructor in C++ are very similar in the sense that they are both quite impossible:

     • You cannot call a constructor in C++.
     • You cannot obtain a pointer to a constructor in C++.

     According to the C++ spec about constructors:

     Constructors have no names and cannot be called directly.

     So, in C++, you do not call constructors. The language does that for you when you use the new keyword, when you declare an object on the stack, etc. The expression new MyClass() might look like a constructor invocation, and it does in fact contain a constructor invocation, and so it might be mistaken for a constructor invocation, but that's not what it is; it is a "new expression", which includes, among other things, an invocation of a constructor. But the other things are crucial: you cannot just skip them and directly invoke the constructor.

     Function pointers of constructors do not exist because normally you cannot take the address of a constructor. If you examine the names exported by the DLL, and somehow figure out which name corresponds to the constructor, and use that name to obtain the entry point of that constructor from the DLL, you are cheating: you are doing something which is not normally supported by the language. As a result, you should not attempt to invoke that entry point. A constructor is only supposed to be invoked by the language.

     Also according to the C++ spec:

     A constructor is a special non-static member function of a class.

     (Emphasis mine.)

     A constructor assumes that memory has been allocated, and proceeds to initialize that memory. The language takes care of the memory allocation, but invoking the constructor directly does not. Since a constructor is non-static, it expects an uninitialized this to be passed to it, but you are not allocating any memory and you are not passing anything to the constructor. The result is exactly as expected: a crash.

     And besides, think about it: the constructor could not be internally allocating the memory, because how would it work then if the object was allocated on the stack? And how would it work if the constructor was being invoked by the constructor of a derived class which presumably occupies more memory?

     You can get your DLL to work by using a factory method. A factory method is a public static method which executes new ClassA() and returns the result, or declares ClassA() and returns it by value. Then, obtain the address of the factory method from the DLL, and invoke it.

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   • What are the differences between using pure C with a C compiler and the "C part" of a C++ compiler?

     Top Answer

     Answered Sep 06, 2010 · 33 votes

     There are a lot of minor nitpicks. One that strikes me as being the most obvious is that in C++, you have to cast the return value of malloc. Also structs are automatically typedefed in C++.

     Always use a C compiler for C code, not C++. C++ isn't perfectly compatible with C.

     A few others:

     • In C, declaring void func(); declares a function that hasn't specifed what its arguments are, whereas in C++, void func(); is equivalent to the C void func(void)', taking no arguments;
     • Prototypes are required in C++, whereas it's generally just a warning in C;
     • The type of character constants (like 'a') is int in C and char in C++;
     • The type of string literals is char [] in C and const char [] in C++;
     • Some legitimate variable names in C, like class, are reserved keywords in C++.

     For all those who don't believe me and are downvoting, check out this C code:

     #include <stdlib.h>-int main(int argc, char **argv) { int *i = malloc(sizeof(int));- return 0;}-

     Compilation under gcc is fine, but compilation under g++ gives the following errors:

     test.c: In function `int main(int, char**)':test.c:4: error: invalid conversion from `void*' to `int*'-

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   • What are the differences between pointer variable's value & address of normal variable and what are the special purpose of pointers in C?

     Top Answer

     Answered Jun 26, 2017 · 5 votes

     Answering questions in reverse order:

     C does not have array variables....but this is really just working with pointers with an alternative syntax.

     This is incorrect, and you need to toss that bookmark in the trash. It's a common misconception that arrays and pointers are the same thing, but they are not. An array expression will be converted to a pointer expression under most circumstances, and array subscripting is accomplished through pointer arithmetic, but an array object is an actual array, not a pointer.

     If pointer also keeps the variable's address in it and at the same time we can get the variable's address using & sign, can't we do the same task pointer does by deriving the address of any variable? I mean if I don't declare it as pointer and use it as int ptr = &i; in 2nd code snippet and use it as normal variable, what would be the differences?

     That code doesn't illustrate why pointers exist, or why they are useful.

     C actually requires us to use pointers in the following cases:

     • To write to a function's parameters;
     • To track dynamically allocated memory;

     Pointers also make dynamic data structures like trees and lists easy to implement, but they aren't required for it (unless you're using dynamic memory allocation in those structures).

     Writing to a function's parameters

     C passes all function arguments by value; the formal parameter in the function definition is a separate object in memory from the actual parameter in the function call, so any change to the formal parameter is not reflected in the actual parameter. For example, assume the following swap function:

     void swap( int a, int b ) { int t = a; a = b; b = t; }-

     This function exchanges the values in a and b. However, when we call the function as

     int x = 4, y = 5;swap( x, y );-

     the values of x and y won't be updated, because they are different objects than a and b. If we want to update x and y, we have to pass pointers to them:

     swap( &x, &y );-

     and update the function definition as follows:

     void swap( int *a, int *b ) { int t = *a; *a = *b; *b = t; }-

     Instead of swapping the contents of a and b, we swap the contents of the objects that a and b point to. This crops up all the time - think about the scanf function, and how you have to use the & operator on scalar arguments.

     Tracking dynamically allocated memory

     The dynamic memory allocation functions malloc, calloc, and realloc all return pointers to dynamic memory buffers; there's no variable associated with that memory as such.

     char *buffer = malloc( sizeof *buffer * some_length );-

     A pointer is the only way to track that memory.

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2. www.geeksforgeeks.org › implementation-on-map-orImplementation on Map or Dictionary Data Structure in C

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   Mar 27, 2023 · Last Updated : 27 Mar, 2023. C programming language does not provide any direct implementation of Map or Dictionary Data structure. However, it doesn’t mean we cannot implement one. In C, a simple way to implement a map is to use arrays and store the key-value pairs as elements of the array .

3. stackoverflow.com › questions › 4384359data structures - Quick Way to Implement Dictionary in C ...

   stackoverflow.com › questions › 4384359

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   typedef struct { int** lines; int isDefined; }mat; mat matA, matB, matC, matD, matE, matF; /* an auxilary struct to be used in a dictionary */ typedef struct { char* str; mat *matrix; }stringToMat; /* creating a 'dictionary' for a mat name to its mat. lower case only! */ stringToMat matCases [] = { { "mat_a", &matA }, { "mat_b", &matB }, { "mat ...

   Code sample

   struct nlist {

     struct nlist *next;

     char *name;

     char *defn;

   };...

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4. People also ask

   Can I create a dictionary in C?

   • You can create anything you want in C. You just won't have native language support for most of it. You can create a dictionary in C, but there is no dictionary built in to the standard C library. A quick search on Google code shows that there are open-source (and generously licensed) C dictionary implementations here and here.

   Do dictionaries exist in C? - Stack Overflow

   stackoverflow.com/questions/9405303/do-dictionaries-exist-in-c

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   Should a dictionary be used in source code?

   • By using a Dictionary in source code, you basically force the compiler's hand; it will do it your way, instead of compromising on performance to gain memory efficiency. So, I would expect most cases in which either a switch statement or a Dictionary could be used in source to perform better when using a Dictionary.

   c# - In a switch vs dictionary for a value of Func, which is faster and why…

   stackoverflow.com/questions/11617091/in-a-switch-vs-dictionary-for-a-value-of-func-which-is-faster-and-why

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   What is a C compiler standard?

   • As a result of the C compiler standard, developers can compile and run other people's code without worrying that their compilers will not work. In order to create such an important building block of the industry, there must be an organization that is responsible for establishing standards

   What is a Compiler? Compilers in C Explained for Beginners

   www.freecodecamp.org/news/what-is-a-compiler-in-c/

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   Is C a compiled language?

   • C is a compiled programming language, like Go, Java, Swift, and Rust. Compiled languages are different from interpeted languages, such as PHP, Ruby, Python, and JavaScript. The difference between compiled and interpeted languages is that a compiled language is directly translated to machine code all at once.

   The C Programming Handbook for Beginners - freeCodeCamp.org

   www.freecodecamp.org/news/the-c-programming-handbook-for-beginners/

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5. www.freecodecamp.org › news › what-is-a-compiler-in-cWhat is a Compiler? Compilers in C Explained for Beginners

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   • What Is A Compiler? An Analogy
   • How C Compilers Work
   • More About Compilers
   • Wrapping Up

   Imagine that you are learning a language (French, Spanish, or Portuguese) and you want to know the meaning of a word or sentence. To do that, you are going to use Google Translate. Thefirst stepis knowing what you will type into Google Translate and checking if it is typed correctly. The second stepis choosing the language you want to convert. For ...

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   Over the years, tech has evolved at an incredible pace. The same applies to compilers. The C compiler has, over time, evolved into many versions. Just like PlayStation – there is the Playstation 2, Playstation 3, Playstation 4, and so on. The same is true for C compilers. Once it was standardized,many versions were created: 1. C89/90, a version of ...

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   What exactly does“gcc -o main main.c -Wall” mean, that we saw in the code above? Let's break it down piece by piece. gccis the command that invokes the compilation process (preprocessing, compilation, assembly, and linking). -o mainindicates that the name of the executable file created by the compilation of "main.c" is going to be called "main". ma...

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   Thanks for reading! Now you understand: 1. What a compiler is 2. The basic history of C compilers 3. What standardization means Hereis the GitHub repository with the code and image files I created.

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   • Author: Tiago Monteiro

6. www.freecodecamp.org › news › the-c-programmingThe C Programming Handbook for Beginners - freeCodeCamp.org

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   Aug 29, 2023 · The gcc part of the command refers to the C compiler, and main.c is the file that contains the C code that you want to compile. Next, enter the following command: ls The ls command lists the contents of the current directory. a.out main.c

7. stackoverflow.com › questions › 11617091In a switch vs dictionary for a value of Func, which is ...

   stackoverflow.com › questions › 11617091

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   Jul 24, 2012 · } By iterating over both methods and comparing, I am getting that the dictionary is slightly faster, even when "a", "b", "c", "d" is expanded to include more keys. Why is this so? Does this have to do with cyclomatic complexity? Is is because the jitter compiles the return statements in the dictionary to native code only once?

8. www.geeksforgeeks.org › c-lexical-analyser-lexerLexical Analyser in C - GeeksforGeeks

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   Jan 3, 2024 · Lexical Analyser in C. Last Updated : 03 Jan, 2024. In C, the lexical analysis phase is the first phase of the compilation process. In this step, the lexical analyzer (also known as the lexer) breaks the code into tokens, which are the smallest individual units in terms of programming.

9. www.freecodecamp.org › news › how-to-define-aDef in C – How to Define a Function in C - freeCodeCamp.org

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   Apr 12, 2024 · How to Call a Function in C. Here is the syntax for calling a function in C: function_name(arguments); Let's break it down: function_name is the name of the function you want to call. It should be the same name you used to define your function. arguments are the values you pass to the function.