Added files

gcd/Makefile

@@ -0,0 +1,31 @@
+CXX := g++
+CFLAGS := -std=c++11 -m64 -Wall -Werror -Wextra -O3
+
+.PHONY: all
+all: bin/gcd
+
+bin:
+	@mkdir -v bin
+
+bin/gcd: src/gcd.cpp | check-cxx-works bin
+	@echo Compiling $<
+	@${CXX} ${CFLAGS} $^ -o $@
+
+.PHONY: install
+install: bin/gcd
+	@cp -v $^ /usr/bin
+
+.PHONY: uninstall
+uninstall: /usr/bin/gcd
+	@rm -v $^
+
+.PHONY: clean
+clean:
+	@rm -rfv bin
+
+.PHONY: mrproper
+mrproper: clean
+
+.PHONY: check-cxx-works
+check-cxx-works:
+	@${CXX} --version >/dev/null 2>&1 || (echo 'Please install a C++ compiler.' && exit 1)

gcd/src/gcd.cpp

@@ -0,0 +1,63 @@
+#include <cstdlib>
+#include <stdio.h>
+#include <errno.h>
+#include <cstring>
+#include <limits.h>
+#include <stdint.h>
+
+/**
+ * @brief Calculate the greatest common divisor (GCD)
+ *
+ * @param a First integer
+ * @param b Second integer
+ * @return greatest common divisor between a and b
+ */
+constexpr int64_t gcd(const int64_t& a, const int64_t& b) noexcept { return a == 0 ? b : gcd(b % a, a); }
+
+/**
+ * @brief Convert a given string to a 64 bit integer
+ *
+ * @param str Input string to convert
+ * @param n Integer output
+ * @return EXIT_SUCCESS if successful otherwise EXIT_FAILURE
+ */
+int32_t sstrtoll(const char* const str, int64_t& n) noexcept {
+	errno = 0;
+	char* endptr = nullptr;
+	const int64_t a = strtoll(str, &endptr, 10);
+
+	switch(errno){
+		case 0:
+			n = a;
+			return EXIT_SUCCESS;
+		case ERANGE:
+			fprintf(stderr, "Error while converting to integer : numerical result out of range (");
+			if(a == LLONG_MIN)
+				fprintf(stderr, "underflow occurred");
+			else if(a == LLONG_MAX)
+				fprintf(stderr, "overflow occurred");
+			else
+				fprintf(stderr, "unspecified");
+			fprintf(stderr, ")\n");
+			return EXIT_FAILURE;
+		default:
+			fprintf(stderr, "Unspecified error occurred while converting to integer: %s\n", strerror(errno));
+			return EXIT_FAILURE;
+	}
+	n = a;
+	return EXIT_SUCCESS;
+}
+
+int32_t main(const int32_t argc, const char* const* argv) noexcept {
+	if (argc != 3){
+		fprintf(stderr, "Syntax : gcd number1 number2\n");
+		return EXIT_FAILURE;
+	}
+	int64_t a, b;
+	if(sstrtoll(argv[1], a) == EXIT_FAILURE) return EXIT_FAILURE;
+	if(sstrtoll(argv[2], b) == EXIT_FAILURE) return EXIT_FAILURE;
+
+	const int64_t hcf = gcd(std::abs(a), std::abs(b));
+	printf("Common factor = %ld\nResult = %ld/%ld\n", hcf, a / hcf, b / hcf);
+	return EXIT_SUCCESS;
+}