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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++

     Top Answer

     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 · 34 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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     4/5

   • 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

   www.geeksforgeeks.org › implementation-on-map-or

   • Cached

   Mar 27, 2023 · Functions used to implement Map in C. The getIndex function searches for a key in the keys array and returns its index if found, or -1 if not found. The insert function inserts a key-value pair into the map. If the key already exists, it updates the value. The get function returns the value of a key in the map, or -1 if the key is not found.

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

   stackoverflow.com › questions › 4384359

   • Cached

   Section 6.6 of The C Programming Language presents a simple dictionary (hashtable) data structure. I don't think a useful dictionary implementation could get any simpler than this. For your convenience, I reproduce the code here. struct nlist { /* table entry: */. struct nlist *next; /* next entry in chain */. char *name; /* defined name */.

   Code sample

   struct nlist {

     struct nlist *next;

     char *name;

     char *defn;

   };...

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4. www.geeksforgeeks.org › compiling-a-c-programCompiling a C Program: Behind the Scenes - GeeksforGeeks

   www.geeksforgeeks.org › compiling-a-c-program

   • Cached

   • How Do We Compile and Run A C Program?
   • What Goes Inside The Compilation Process?
   • Pre-Processing
   • Compiling
   • Assembling
   • Linking

   We first need a compiler and a code editor to compile and run a C Program. The below example is of an Ubuntu machine with GCC compiler.

   See full list on geeksforgeeks.org

   A compiler converts a C program into an executable. There are four phases for a C program to become an executable: 1. Pre-processing 2. Compilation 3. Assembly 4. Linking By executing the below command, we get all intermediate files in the current directory along with the executable. The following screenshot shows all generated intermediate files. ...

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   This is the first phase through which source code is passed. This phase includes: 1. Removal of Comments 2. Expansion of Macros 3. Expansion of the included files. 4. Conditional compilation The preprocessed output is stored in the filename.i. Let’s see what’s inside filename.i: using $vi filename.i In the above output, the source file is filled wi...

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   The next step is to compile filename.i and produce an; intermediate compiled output file filename.s. This file is in assembly-level instructions. Let’s see through this file using$nano filename.s terminal command. The snapshot shows that it is in assembly language, which the assembler can understand.

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   In this phase the filename.s is taken as input and turned into filename.o by the assembler. This file contains machine-level instructions. At this phase, only existing code is converted into machine language, and the function calls like printf() are not resolved. Let’s view this file using $vi filename.o

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   This is the final phase in which all the linking of function calls with their definitions is done. Linker knows where all these functions are implemented. Linker does some extra work also, it adds some extra code to our program which is required when the program starts and ends. For example, there is a code that is required for setting up the envir...

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5. medium.com › @itbamalahat › building-a-dictionary-inBuilding a Dictionary in C Using Tries: A Step-by-Step Guide

   medium.com › @itbamalahat › building-a-dictionary-in

   • Cached

   Apr 7, 2024 · dictionary.c: Implementation of dictionary operations. dictionary.h : Header file containing function declarations for dictionary operations. fileio.c : File input/output operations.

6. norasandler.com › 2018/06/27 › Write-a-Compiler-9C Compiler, Part 9: Functions - Nora Sandler

   norasandler.com › 2018/06/27 › Write-a-Compiler-9

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   Jun 27, 2018 · C Compiler, Part 9: Functions. Jun 27, 2018. This is the ninth post in a series. Read part 1 here. In this post we’re adding function calls! This is a particularly exciting post because we get to talk about calling conventions and stack frames and some weird corners of the C11 standard. Plus, by the end of this post we’ll be able to compile ...

7. groups.seas.harvard.edu › courses › cs153CS153: Compilers Lecture 1: Introduction - Harvard University

   groups.seas.harvard.edu › courses › cs153

   •What can[’t] a compiler do well? •Architecture designers •Interdependence between compiler and architecture •See Intel iAPX 432 and Intel Itanium (compiler-related) failures; register windows •These days, architecture folks use compilers too! •API designers •A language is the ultimate API •c.f., Facebook 11

8. People also ask

   What is a compiler in C?

   • The compilation is the process of converting the source code of the C language into machine code. As C is a mid-level language, it needs a compiler to convert it into an executable code so that the program can be run on our machine. The C program goes through the following phases during compilation: How do we compile and run a C program?

   Compiling a C Program: Behind the Scenes - GeeksforGeeks

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   How do we compile a C program?

   • The C program goes through the following phases during compilation: How do we compile and run a C program? We first need a compiler and a code editor to compile and run a C Program. The below example is of an Ubuntu machine with GCC compiler. We first create a C program using an editor and save the file as filename.c $ vi filename.c

   Compiling a C Program: Behind the Scenes - GeeksforGeeks

   www.geeksforgeeks.org/compiling-a-c-program-behind-the-scenes/

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   How does a compiler convert a C program into an executable?

   • A compiler converts a C program into an executable. There are four phases for a C program to become an executable: By executing the below command, we get all intermediate files in the current directory along with the executable. $gcc -Wall -save-temps filename.c –o filename

   Compiling a C Program: Behind the Scenes - GeeksforGeeks

   www.geeksforgeeks.org/compiling-a-c-program-behind-the-scenes/

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   What is the difference between CC & $ in C?

   • This assumes the name of the C compiler is in a macro named CC (implicitly defined like CC=gcc) and allows you to specify any flags you care about in a macro named CFLAGS (e.g., CFLAGS=-O3 to turn on optimization) and $< is a special macro that expands to the name of the source file.

   C error: undefined reference to function, but it IS defined

   stackoverflow.com/questions/5559250/c-error-undefined-reference-to-function-but-it-is-defined

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9. www.freecodecamp.org › news › how-to-use-functions-in-cHow to Use Functions in C - Explained With Examples

   www.freecodecamp.org › news › how-to-use-functions-in-c

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   Apr 6, 2023 · For example, we can use the following code to call the sum function that we defined earlier: int a = 5; int b = 10; int c = sum(a, b); In this code, we are calling the sum function with a and b as its parameters. The function returns the sum of a and b, which is then stored in the variable c.