[doc] Revise howto (#3222)

Improve howto

docs/examples/Makefile

@@ -0,0 +1,31 @@
+project_root_dir := $(strip $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST)))))
+
+runnable := $(project_root_dir)/ccexample
+
+include_dir := $(project_root_dir)/incl 
+object_dir := $(project_root_dir)/objs
+source_dir := $(project_root_dir)/src
+sources := $(wildcard $(source_dir)/*.c)
+objects := $(patsubst $(source_dir)/%.c,$(object_dir)/%.c.o,$(sources))
+depends := $(patsubst $(source_dir)/%.c,$(object_dir)/%.c.d,$(sources))
+
+CFLAGS = -MMD -MP -g -std=c99 -Wall
+CFLAGS += -I $(include_dir)
+
+all: $(runnable)
+
+$(runnable): $(objects)
+	$(CC) $(LINKFLAGS) $^ -o $@
+
+$(objects): $(object_dir)/%.c.o: $(source_dir)/%.c
+	@mkdir --parents $(object_dir)
+	$(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
+
+.PHONY: clean
+clean:
+	rm --recursive --force $(object_dir)
+	rm --force $(runnable)
+
+ifneq ($(filter clean,$(MAKECMDGOALS)),clean)
+-include $(depends)
+endif

docs/examples/incl/divide.h

@@ -0,0 +1,6 @@
+#ifndef DIVIDE_H
+#define DIVIDE_H
+
+long divide(long numerator, long denominator);
+
+#endif // DIVIDE_H

docs/examples/src/divide.c

@@ -0,0 +1,6 @@
+#include "divide.h"
+
+long divide(long numerator, long denominator)
+{
+    return numerator / denominator;
+}

docs/examples/src/main.c

@@ -0,0 +1,24 @@
+#include "divide.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+int main(int argc, char* argv[])
+{
+    long result;
+    long test_case;
+
+    if(argc < 1) {
+        printf("Please specify testcase id.\n");
+        return 1;
+    }
+    if (strcmp(argv[1], "all")) {
+        test_case = strtol(argv[1], NULL, 10);
+        // Division by zero, only detected when ctu analysis is on
+        result = divide(test_case, 0);
+    }
+
+    return (int)result;
+}