Objectives

1. Begin a review of C++
2. Review our coding environment
3. Review the edit-compile-execute cycle
4. Review compiler flags
5. Review a simple Makefile

Notes

• Environment
  • prog1.cs.pennwest.edu
  • devweb1.cis.pennwest.edu
    • Both use your PennWest credentials.
    • You will need to vpn in to get access from off campus.
  • Prog1 has a more modern compiler, so I will be using it.
    • The final arbitrator for does your program compile is prog1.
    • g++ --version
  • You can access these machines a number of ways.
    • I will use putty, winscp and vi.
    • You will likely use visual studio code.
    • But this doesn't matter as long as you can use the machine.
• Task 1: I would like to simulate a six sided die.
  • How can we generate random numbers in c++?
  • I assume we discuss rand, srand and perhaps time(nullptr)
  • And probably some version of this code

    #include <iostream>
    #include <iomanip>
    
    using namespace std;
    int main() {
       srand(time(nullptr));
       for(int i = 0; i < 10; ++i) {
           cout << rand() % 6 + 1  << endl;
       }
       return 0;

  • Make sure you understand rand, srand from this discussion.
  • Make sure you remember/understand how to edit/compile/execute
  • Make sure you understand % 6 + 1
• Compiler options
  • Remember, the compiler can help us detect bad code.
  • For now I want you to use

      -Wall -Wextra -Wpedantic -Wshadow -Wconversion -std=c++23 -g -O2 

  • These will work on prog1, but not on devweb1, it doesn't have c++23
    • -Wall "This enables all the warnings about constructions that some users consider questionable, and that are easy to avoid (or modify to prevent the warning), even in conjunction with macros."
    • -Wextra "This enables some extra warning flags that are not enabled by -Wall."
    • -Wpedantic "Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use forbidden extensions, and some other programs that do not follow ISO C and ISO C++. For ISO C, follows the version of the ISO C standard specified by any -std option used."
    • -Wshadow" Warn whenever a local variable or type declaration shadows another variable, parameter, type, class member (in C++) ..., or whenever a built-in function is shadowed. Note that in C++, the compiler warns if a local variable shadows an explicit typedef, but not if it shadows a struct/class/enum."
    • -Wconversion "Warn for implicit conversions that may alter a value."
    • -std= "Determine the language standard", this let's us use the c++23 standard
    • -g Set the debugging level,
    • -O2 set the optimization level.
    • All quotes from the man page.
  • Compile with

    g++ -Wall -Wextra -Wpedantic -Wshadow -Wconversion -std=c++23 -g -O2    task1pre.cpp   -o task1pre

• A simple Makefile
  • Remember make is a utility for building program fro source code.
  • It is very useful when you have multiple files.
  • But it is also useful when you want to use a set of compiler flags too.
  • Create a file called Makefile or makefile, but not makefile.txt or Makefile.txt
  • Add a line at the top of the file

    • OBJS = task1

    • This assumes that task1.cpp holds your code.
    • You will add to this if you have other program.s
    • This defines a variable that holds a list of the programs we are working with (not files)
  • Add a line :

    • CXXFLAGS = -Wall -Wextra -Wpedantic -Wshadow -Wconversion -std=c++23 -g -O2 

    • This will tell make to use these flags any time it compiles a program.
  • Add a line

    •  all: ${OBJS}

    • This defines a target
    • The target all, or the first target, is the default if you just type make at the command line.
    • ${OBJS} accesses the values in the variable OBJS, Make uses an old programming language.
  • Add the following lines

    • clean:
          rm -rf ${OBJS} *.o 

    • This builds a new target, clean, which will remove all executable files (in the build list) and object files.
    • Make sure that
      • There is a tab before rm, make is old and this marks the body of the target. These are the commands to apply to build that target.
      • There is no space in the *.o, especially after the *

  • OBJS = task1
    
    CXXFLAGS = -Wall -Wextra -Wpedantic -Wshadow -Wconversion -std=c++23 -g -O2
    
    all: ${OBJS}
    
    clean:
        rm -rf ${OBJS} *.o