Rolling A Die

Objectives

We would like to :

Begin a review of C++
Review our coding environment
Review the edit-compile-execute cycle
Review compiler flags
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 -f ${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 -f ${OBJS} *.o 
```