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Understanding and Using C Pointers

Name: Understanding and Using C Pointers
Author: Richard M Reese
ISBN: 9781449344184

by Richard M Reese

May 2013

Beginner to intermediate

223 pages

5h 55m

English

O'Reilly Media, Inc.

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Preface
Why This Book Is DifferentThe ApproachAudienceOrganizationSummaryConventions Used in This BookUsing Code ExamplesSafari® Books OnlineHow to Contact Us
1. Introduction
Pointers and MemoryWhy You Should Become Proficient with PointersDeclaring PointersHow to Read a DeclarationAddress of OperatorDisplaying Pointer ValuesVirtual memory and pointersDereferencing a Pointer Using the Indirection OperatorPointers to FunctionsThe Concept of NullTo NULL or not to NULLPointer to voidGlobal and static pointersPointer Size and TypesMemory ModelsPredefined Pointer-Related TypesUnderstanding size_tUsing the sizeof operator with pointersUsing intptr_t and uintptr_tPointer OperatorsPointer ArithmeticAdding an integer to a pointerPointers to void and additionSubtracting an integer from a pointerSubtracting two pointersComparing PointersCommon Uses of PointersMultiple Levels of IndirectionConstants and PointersPointers to a constantConstant pointers to nonconstantsConstant pointers to constantsPointer to (constant pointer to constant)Summary
2. Dynamic Memory Management in C
Dynamic Memory AllocationMemory LeaksLosing the addressHidden memory leaksDynamic Memory Allocation FunctionsUsing the malloc FunctionTo cast or not to castFailing to allocate memoryNot using the right size for the malloc functionDetermining the amount of memory allocatedUsing malloc with static and global pointersUsing the calloc FunctionUsing the realloc FunctionThe alloca Function and Variable Length ArraysDeallocating Memory Using the free FunctionAssigning NULL to a Freed PointerDouble FreeThe Heap and System MemoryFreeing Memory upon Program TerminationDangling PointersDangling Pointer ExamplesDealing with Dangling PointersDebug Version Support for Detecting Memory LeaksDynamic Memory Allocation TechnologiesGarbage Collection in CResource Acquisition Is InitializationUsing Exception HandlersSummary
3. Pointers and Functions
Program Stack and HeapProgram StackOrganization of a Stack FramePassing and Returning by PointerPassing Data Using a PointerPassing Data by ValuePassing a Pointer to a ConstantReturning a PointerPointers to Local DataPassing Null PointersPassing a Pointer to a PointerWriting your own free functionFunction PointersDeclaring Function PointersUsing a Function PointerPassing Function PointersReturning Function PointersUsing an Array of Function PointersComparing Function PointersCasting Function PointersSummary
4. Pointers and Arrays
Quick Review of ArraysOne-Dimensional ArraysTwo-Dimensional ArraysMultidimensional ArraysPointer Notation and ArraysDifferences Between Arrays and PointersUsing malloc to Create a One-Dimensional ArrayUsing the realloc Function to Resize an ArrayPassing a One-Dimensional ArrayUsing Array NotationUsing Pointer NotationUsing a One-Dimensional Array of PointersPointers and Multidimensional ArraysPassing a Multidimensional ArrayDynamically Allocating a Two-Dimensional ArrayAllocating Potentially Noncontiguous MemoryAllocating Contiguous MemoryJagged Arrays and PointersSummary
5. Pointers and Strings
String FundamentalsString DeclarationThe String Literal PoolWhen a string literal is not a constantString InitializationInitializing an array of charInitializing a pointer to a charInitializing a string from standard inputSummary of string placementStandard String OperationsComparing StringsCopying StringsConcatenating StringsPassing StringsPassing a Simple StringPassing a Pointer to a Constant charPassing a String to Be InitializedPassing Arguments to an ApplicationReturning StringsReturning the Address of a LiteralReturning the Address of Dynamically Allocated MemoryReturning the address of a local stringFunction Pointers and StringsSummary
6. Pointers and Structures
IntroductionHow Memory Is Allocated for a StructureStructure Deallocation IssuesAvoiding malloc/free OverheadUsing Pointers to Support Data StructuresSingle-Linked ListUsing Pointers to Support a QueueUsing Pointers to Support a StackUsing Pointers to Support a TreeSummary
7. Security Issues and the Improper Use of Pointers
Pointer Declaration and InitializationImproper Pointer DeclarationFailure to Initialize a Pointer Before It Is UsedDealing with Uninitialized PointersPointer Usage IssuesTest for NULLMisuse of the Dereference OperatorDangling PointersAccessing Memory Outside the Bounds of an ArrayCalculating the Array Size IncorrectlyMisusing the sizeof OperatorAlways Match Pointer TypesBounded PointersString Security IssuesPointer Arithmetic and StructuresFunction Pointer IssuesMemory Deallocation IssuesDouble FreeClearing Sensitive DataUsing Static Analysis ToolsSummary
8. Odds and Ends
Casting PointersAccessing a Special Purpose AddressAccessing a PortAccessing Memory using DMADetermining the Endianness of a MachineAliasing, Strict Aliasing, and the restrict KeywordUsing a Union to Represent a Value in Multiple WaysStrict AliasingUsing the restrict KeywordThreads and PointersSharing Pointers Between ThreadsUsing Function Pointers to Support CallbacksObject-Oriented TechniquesCreating and Using an Opaque PointerPolymorphism in CSummary
Index

About the Author
Colophon
Copyright

Content preview from Understanding and Using C Pointers

Chapter 3. Pointers and Functions

Pointers contribute immensely to a function’s capability. They allow data to be passed and modified by a function. Complex data can also be passed and returned from a function in the form of a pointer to a structure. When pointers hold the address of a function, they provide a means to dynamically control a program’s execution flow. In this chapter, we will explore the power of pointers as used with functions and learn how to use them to solve many real-world problems.

To understand functions and their use with pointers, a good understanding of the program stack is needed. The program stack is used by most modern block-structured languages, such as C, to support the execution of functions. When a function is invoked, its stack frame is created and then pushed onto the program stack. When the function returns, its stack frame is popped off of the program stack.

When working with functions, there are two areas where pointers become useful. The first is when we pass a pointer to a function. This allows the function to modify data referenced by the pointer and to pass blocks of information more efficiently.

The second area is declaring a pointer to a function. In essence, function notation is pointer notation. The function’s name evaluates to the address of the function, and the function’s parameters are passed to the function. As we will see, function pointers provide additional capability to control the execution flow of a program.

In this section, we ...

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Understanding and Using C Pointers

by Richard M Reese

Chapter 3. Pointers and Functions

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