Homework 2, Compiler Flags and Make.

Short Description:

This assignment is worth 5 points.

Goals

• Understand the basics compiling programs.
• Understand compiler flags.
• Know how to use make to build a single file program.
• Understand the advantages of using compiler flags.

Formal Description

1. Start a word document.
   • Add you name and class identification information at the top.
2. Make a new folder (directory) for this homework. Do all work in this directory.
   • If you are unsure how to do this, please ask for assistance.
   • Change to the new directory.
3. Create a file called Makefile
   • It should contain a single line

   • CXXFLAGS = -g -O3 -Wpedantic -Wall -Wextra -Wmisleading-indentation -Wunused -Wuninitialized -Wshadow -Wconversion -D_GLIBCXX_ASSERTIONS -std=c++17
              

   • This file defines the command line flags we would like make to use when compiling code.
4. Create the file hw2a.cpp.

   • #include <iostream>
     
     using namespace std;
     
     int main() {
         int i;
     
         while (i < 10) {
             int i = 4;
             i += i;
             cout << " i = " << i << endl;
         }
     
         return 0;
     }

   • If you must, you may adjust the bracket placement.
5. In the word document, answer Question 1: What will happen when hw2a.cpp is compiled?"
   • This code is legal code, and should compile unless you have introduced syntax errors.
   • Provide the best answer you can, without compiling or running the code.
   • Credit for this question is based on providing an answer, not on the correctness of the answer.
6. Compile the code with g++ -o hw2a hw2a.cpp
   • In the word document, answer Question 2: What happened when hw2a.cpp was compiled with g++ -o hw2a hw2a.cpp.
7. Make is a utility that will compile code for us based on the configuration file Makefile
   • Remove the executable produced above by typing rm hw2a
     • Do not remove hw2a.cpp, or any other file, just hw2a.
   • Type make -n hw2a
     • This will show the command make would execute
     • But it does not execute this command.
     • If it says make: 'hw2a' is up to date. you need to remove the executable hw2a as directed above.
   • Notice that make is running g++, but with a bunch of command line flags.
8. When compiling you can receive two or three different types of messages
   • Syntax messages describe syntax errors.
     • Syntax errors keep programs from compiling.
     • I expect you are reasonably good at eliminating these.
     • And they must be eliminated from all code you turn in.
   • Warnings are messages that describe legal syntax that is probably used incorrectly.
     • Warnings usually indicate bad code.
     • And they must be eliminated from all code you turn in.
   • In your word document, Question 3: Provide an example of a statement that produces a syntax error. Clearly describe what this syntax error is.
9. Compile your program using make
   • Type make hw2a
   • In your word document answer Question 4: What are the compiler warnings produced when using the command line flags to g++ and what do they mean?
     • I received two warnings and a note.
     • I expect a correct answer to this question.
     • If you are unsure of the warning that involves shadowing see pages 404-408 of your book.
10. What happens when you run this code?
    • Remember ctrl-c (hold the control key and press c) will break out of an infinite loop.
    • In your word document answer Question 5: Why does how2a.cpp execute an infinite loop and how is this related to the shadow declaration warning?
    • I expect a correct answer to this question.
11. Create the file hw2b.cpp containing

    • #include <iostream>
      
      using namespace std;
      
      int main() {
          int i;
      
          while (i < 10)
              cout << i << endl;
              i++;
      
          return 0;
      } 

    • This code is syntax error free and should compile.
    • But do not add any other code. This may annoy some of you, but just do it.
    • Compile this code by hand (g++ -o hw2b hw2b.cpp) to assure yourself it compiles without errors.
    • Run the program (remember ctrl-c to kill infinite loops).
    • In your word document answer the following question Question 6: What caused the infinite loop in hw2b.cpp
    • Compile this code with the following g++ -o hw2b -Wmisleading-indentation hw2b.cpp
    • In your word document answer the following Question 7: What does the command line flag -Wmisleading-indentation cause the compiler to report?
    • Compile the code with make make hw2b
      • You will probably have to remove the executable rm hw2b
    • In your word document answer the following question Question 8: How does make simplify the compiling process with respect to compiler flags?
12. Three additional make related items.
    • You can build rules to perform frequent actions.
      • remove the file hw2a
      • Type make What happens?
      • Add the following line to your Makefile

      • CXXFLAGS = -g -O3 -Wpedantic -Wall -Wextra -Wmisleading-indentation -Wunused -Wuninitialized -Wshadow -Wconversion -D_GLIBCXX_ASSERTIONS -std=c++17
        
        all: hw2a 

      • Now type make What happens?
      • By adding the line all: hw2a we declared a default target. (I am sort of lying, but it will do).
      • We could change the line to be

        • all: hw2a hw2b hw2c 

      • This would build all three programs by just typing make, try it.
    • You can add variables to Makefiles
      • Change your Makefile to be

      • OBJS = hw2a hw2b hw2c
        CXXFLAGS = -g -O3 -Wpedantic -Wall -Wextra -Wmisleading-indentation -Wunused -Wuninitialized -Wshadow -Wconversion -D_GLIBCXX_ASSERTIONS -std=c++17
        
        all: ${OBJS}

      • This defines a variable OBJS which are the objects we wish to build.
      • Then tells make when we make all we really want to build these objects.
      • The ${OBJS} is a little strange, but roll with it.
    • You can ask make to "clean" up your directory.
      • CAUTION in the last line, starts with a tab.
        • This is required.
      • Change your makefile to be:

      • OBJS = hw2a hw2b hw2c
        CXXFLAGS = -g -O3 -Wpedantic -Wall -Wextra -Wmisleading-indentation -Wunused -Wuninitialized -Wshadow -Wconversion -D_GLIBCXX_ASSERTIONS -std=c++17
        
        all: ${OBJS}
        
        clean:
                rm -f ${OBJS}
        

      • Type make clean
      • What happens?

Required Files

Submission