feat: add UB-oriented isEven program

.gitignore

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+*.o
+*.s
+main

README.md

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+This program, compiled with clang 12+, should work.
+However, it is using an undefined behaviour in the `isEven.cpp` file.
+
+```
+make run
+```
+
+Originates from https://twitter.com/jckarter/status/1428072308351016969

isEven.cpp

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+#include "isEven.h"
+
+bool isEven(int x) {
+  switch (x) {
+  case 0:
+    return true;
+  case 1:
+    return false;
+  case 2:
+    return true;
+  case 3:
+    return false;
+
+  // Why defininfg more cases when the compiler can do it ?
+
+  default:
+    return isEven(x);
+  }
+}

isEven.h

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+bool isEven(int);

main.cpp

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+#include "isEven.h"
+#include <iostream>
+
+int main() {
+  int x;
+  while (true) {
+    std::cout << "BENOIT< Is this number even ? ";
+    std::cin >> x;
+
+    if (isEven(x)) {
+      std::cout << "BENOIT> True\n\n";
+    } else {
+      std::cout << "BENOIT> False\n\n";
+    }
+  }
+  return 0;
+}

makefile

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+CFLAGS=-O3
+
+all: main
+
+main: isEven.o main.o
+	@clang++ main.o isEven.o -lstdc++ --output main ${CFLAGS}
+
+.PHONY: build-assembly
+build-assembly:
+	@clang++ lolilol.cpp -S -masm=intel ${CFLAGS}
+
+.PHONY: run
+run: main
+	./main
+
+
+main.o: isEven.h
+
+
+%.o: %.cpp
+	@clang++ -o $@ -c $< ${CFLAGS}
+
+.PHONY: clean
+clean:
+	@rm -rf *.s *.o main