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编程代写｜CMPSC 311 – Introduction to Systems Programming

编程代写｜CMPSC 311 – Introduction to Systems Programming

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这是一篇来自美国的系统编程代写

 

Building a program 101

  • There are two phases of building a program, compiling and linking
  • gcc is used to build the program
  • ld can be used to link the program (or gcc)

Compiling a program

  • You will run a command to compile gcc <source code> [options]
  • Interesting options
  • -c (tells the compiler to just generate the object files)
  • -Wall (tells the compiler to show all warnings)
  • -g (tells the compiler to generate debug information)
  • -o <filename>.o (write output to file)
  • An example

gcc hello.c -c -Wall -g -o hello.o

Linking a program

  • You will run a command to link gcc <object files> [options]
  • Interesting options
  • -l<lib> (link with a library)
  • -g (tells the compiler to generate debug information)
  • -o <filename> (write output to file)
  • An example,gcc hello.o goodbye.o -g -lmyexample -o hello

What is a “static” library?

  • A library is a collection of related code and functions that are “linked” against a C program.
  • The library “exports” “symbols”
  • You program object code has “unresolved symbols”
  • The linker pulls chunks of the library containing those symbols and places them into the program
  • The program is done when all the pieces are resolved
  • It is called “static” linking because this is done at link time

Building a static library

  • A statically linked library produces object code that is inserted into program at link time.
  • You are building an “archive” of the library which the linker uses to search for and transfer code into your program.ar rcs lib<libname>.a <object files>
  • To run the command, use
  • Library naming: with very few exceptions all static libraries are named library.a, e.g.,ar rcs libmyexample.a a.o b.o c.o d.o
  • You link against the name of the library, not against the name of the file in which the library exists (see linking)
  • A statically linked library produces object code that is inserted into program at link time.
  • You are building an “archive” of the library which the linker uses to search for and transfer code into your program.
  • To run the command, use
  • Library naming: with very few exceptions all static libraries are named library.a, e.g.,
  • You link against the name of the library, not against the name of the file in which the library exists (see linking)
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