Introduce nested exception printing

Author: svorenova

src/util/Makefile

@@ -96,6 +96,7 @@ SRC = arith_tools.cpp \
       unicode.cpp \
       union_find.cpp \
       union_find_replace.cpp \
+      unwrap_nested_exception.cpp \
       xml.cpp \
       xml_expr.cpp \
       xml_irep.cpp \

src/util/unwrap_nested_exception.cpp

@@ -0,0 +1,53 @@
+/*******************************************************************\
+
+Module: util
+
+Author: Diffblue Ltd.
+
+\*******************************************************************/
+
+#include "unwrap_nested_exception.h"
+#include "invariant.h"
+#include "string_utils.h"
+#include "suffix.h"
+
+#include <sstream>
+#include <vector>
+
+/// Given a potentially nested exception, produce a string with all of nested
+/// exceptions information. If a nested exception string contains new lines
+/// then the newlines are indented to the correct level.
+/// \param e: The outer exeception
+/// \param level: How many exceptions have already been unrolled
+/// \return A string with all nested exceptions printed and indented
+std::string unwrap_exception(const std::exception &e, int level)
+{
+  const std::string msg = e.what();
+  std::vector<std::string> lines;
+  split_string(msg, '\n', lines, false, true);
+  std::ostringstream message_stream;
+  message_stream << std::string(level, ' ') << "exception: ";
+  join_strings(
+    message_stream, lines.begin(), lines.end(), "\n" + std::string(level, ' '));
+
+  try
+  {
+    std::rethrow_if_nested(e);
+  }
+  catch(const std::exception &e)
+  {
+    std::string nested_message = unwrap_exception(e, level + 1);
+    // Some exception messages already end in a new line (e.g. as they have
+    // dumped an irept. Most do not so add a new line on.
+    if(nested_message.back() != '\n')
+    {
+      message_stream << '\n';
+    }
+    message_stream << nested_message;
+  }
+  catch(...)
+  {
+    UNREACHABLE;
+  }
+  return message_stream.str();
+}

src/util/unwrap_nested_exception.h

@@ -0,0 +1,17 @@
+/*******************************************************************\
+
+Module: util
+
+Author: Diffblue Ltd.
+
+\*******************************************************************/
+
+#ifndef CPROVER_UTIL_UNWRAP_NESTED_EXCEPTION_H
+#define CPROVER_UTIL_UNWRAP_NESTED_EXCEPTION_H
+
+#include <exception>
+#include <string>
+
+std::string unwrap_exception(const std::exception &e, int level = 0);
+
+#endif // CPROVER_UTIL_UNWRAP_NESTED_EXCEPTION_H