Which Variable Should be Declared as Registers in a C Program?

Question9: Which Variable Should be Declared as Registers in a C Program Answer: Recall that ‘x86-64 bit’ architecture allows up to max of 6 arguments being passed to a procedure to be stored via registers. Register allocation eliminates the need to fetch the arguments from memory thereby reducing the overheads incurred in reading from and … Read more

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What Happens During Function Epilogue Phase?

Question: What Happens During Function Epilogue Phase? Answer: As we know that called function has three components viz., function prologue, function body and lastly function epilogue. Function prologue begins with creating space for local variables, saved registers and for parameters being passed to a procedure. Function body is where useful work is performed. When function … Read more

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What is a Stack Frame, and How does it Work in the Context of a Function Call?

Question: How Stack Frame is Organised and How Protocols for Calling and Returning from Functions are Interpreted Answer: Unlike IA32 ISA, ‘x86-64 bit’ architecture implements stack differently. Because of max 6 registers allowed for parameters being passed to a procedure to be strored via registers, some procedures do not need stack at all. At times … Read more

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Difference between Frame Pointer and Stack Pointer

Question: What is Difference Between Frame Pointer and Stack Pointer Answer: Consider fragment of C code below, long int simple_long(long int *xp, long int y) { long int t = *xp + y; *xp = t;   return t; } When gcc is run on x86-64 bit architecture with the command-line gcc -osl32 -S -m32 … Read more

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Is this True that all Variables Declared to be Registers in a C Program Allocated Necessarily in Register Memory

Question: Is this true that all the Variables Declared to be Registers in a C Program Given Allocation Necessarily in Register Memory Answer: Thus far, we have become familiar with ‘general purpose register set of x86-64 bit’ architecture. There are 6 registers reserved for obtaining arguments being passed to a procedure. These are: %rdi %rsi … Read more

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Do Local Variables and Function Prototypes in a C Program Produce any Assembly Code

Question6: Do Local Variables and Function Prototypes in a C Program Produce any Assembly Code Answer: This is an easy task! Let’s experiment with our machine to confirm this! I’ve written below a C function within which declared several variables, pointers and also a few function prototypes. void lvar_funpt() { long a1, a2, a3, a4, … Read more

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Code, Data, Heap and Stack Segements in C

Question: Define Different Segments of a C Program’s Address Space Answer: Generally, every program we write contains instructions, initialized and uninitialized data, variables local to a function and instructions for dynamically allocated storage. Once the program is done with writing we, then, compile it to generate a default output “a.out”, an executable linkable format (ELF) … Read more

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What is Stack Frame in C?

Question: What is Stack Frame in C Answer: As we know that when one function calls other function, a runtime stack is created for the called function for execution of its instructions, holding automatic variables and other values and return address. Prologue component of called function begins by reserving space for local variables and other … Read more

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Function Prologue and Epilogue in C

Question4: What do Prologue and Epilogue Terms Stand For in Context with Functions in a C Program Answer: Every functions has three components, function prologue, function body and function epilogue. Function prologue is part of function does all work needed to start up the function. It begins by reserving space for local variables and other … Read more

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What are the Runtime Environment Limits in C?

Question: What are the Limits of One’s Runtime Environment Answer: To begin with exploring one’s runtime environment, first step is to obtain assembly language listing for your compiler. On Linux system, ‘-S’ compiler option causes compiler to produce assembly code for your C program in a file that has ‘.s’ suffix. For example, say, ‘hello.c’ … Read more

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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