Update 003_exception_std_rethrow_if_nested.cpp

Author: ls-Brynn

cpp_11/003_exception_std_rethrow_if_nested.cpp

@@ -1 +1,48 @@
-1
+#include <iostream>
+#include <stdexcept>
+#include <exception>
+#include <string>
+#include <fstream>
+ 
+// prints the explanatory string of an exception. If the exception is nested,
+// recurses to print the explanatory of the exception it holds
+void print_exception(const std::exception& e, int level =  0)
+{
+    std::cerr << std::string(level, ' ') << "exception: " << e.what() << '\n';
+    try {
+        std::rethrow_if_nested(e);
+    } catch(const std::exception& e) {
+        print_exception(e, level+1);
+    } catch(...) {}
+}
+ 
+// sample function that catches an exception and wraps it in a nested exception
+void open_file(const std::string& s)
+{
+    try {
+        std::ifstream file(s);
+        file.exceptions(std::ios_base::failbit);
+    } catch(...) {
+        std::throw_with_nested( std::runtime_error("Couldn't open " + s) );
+    }
+}
+ 
+// sample function that catches an exception and wraps it in a nested exception
+void run()
+{
+    try {
+        open_file("nonexistent.file");
+    } catch(...) {
+        std::throw_with_nested( std::runtime_error("run() failed") );
+    }
+}
+ 
+// runs the sample function above and prints the caught exception
+int main()
+{
+    try {
+        run();
+    } catch(const std::exception& e) {
+        print_exception(e);
+    }
+}