test(util/exception): experiment with exceptions with nested std::function

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/tests/util/exception.cpp

@@ -5,6 +5,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Author: Leonardo de Moura
 */
 #include <string>
+#include <functional>
 #include "util/test.h"
 #include "util/exception.h"
 #include "util/sstream.h"
@@ -42,10 +43,51 @@ static void tst4() {
     }
 }
 
+class ex : public exception {
+    std::function<char const *()> m_f;
+    ex(std::function<char const *()> const & f):m_f(f) {}
+public:
+    template<typename F> ex(F && f):m_f(f) {}
+    virtual exception * clone() const { return new ex(m_f); }
+    virtual void rethrow() const { throw *this; }
+    virtual char const * what() const noexcept { return m_f(); }
+};
+
+static void throw_ex() {
+    int x = 10;
+    std::string msg = "foo";
+    throw ex([=]() {
+            static std::string m;
+            std::ostringstream buffer;
+            buffer << "error, x: " << x << " " << msg;
+            m = buffer.str();
+            return m.c_str();
+        });
+}
+
+static void throw_catch_rethrow() {
+    try {
+        throw_ex();
+    } catch (ex & e) {
+        std::cout << "CATCH 1: {" << e.what() << "}\n";
+        std::unique_ptr<exception> new_e(e.clone());
+        new_e->rethrow();
+    }
+}
+
+static void tst5() {
+    try {
+        throw_catch_rethrow();
+    } catch (ex & e) {
+        std::cout << "CATCH 2: {" << e.what() << "}\n";
+    }
+}
+
 int main() {
     tst1();
     tst2();
     tst3();
     tst4();
+    tst5();
     return has_violations() ? 1 : 0;
 }