Store error in string to avoid dangling pointers

Author: thk123

src/solvers/flattening/flatten_byte_extract_exceptions.h

@@ -36,21 +36,24 @@ class non_const_array_sizet : public flatten_byte_extract_exceptiont
     : flatten_byte_extract_exceptiont("cannot unpack array of non-const size"),
       max_bytes(max_bytes),
       array_type(array_type)
-  {
-  }
-
-  const char *what() const noexcept override
   {
     std::ostringstream error_message;
     error_message << runtime_error::what() << "\n";
     error_message << "array_type: " << array_type.pretty();
     error_message << "\nmax_bytes: " << max_bytes.pretty();
-    return error_message.str().c_str();
+    computed_error_message = error_message.str();
+  }
+
+  const char *what() const noexcept override
+  {
+    return computed_error_message.c_str();
   }
 
 private:
   exprt max_bytes;
   array_typet array_type;
+
+  std::string computed_error_message;
 };
 
 class non_byte_alignedt : public flatten_byte_extract_exceptiont
@@ -65,24 +68,27 @@ class non_byte_alignedt : public flatten_byte_extract_exceptiont
       struct_type(struct_type),
       component(component),
       byte_width(byte_width)
-  {
-  }
-
-  const char *what() const noexcept override
   {
     std::ostringstream error_message;
     error_message << runtime_error::what() << "\n";
     error_message << "width: " << byte_width << "\n";
     error_message << "component:" << component.get_name()  << "\n";
     error_message << "struct_type: " << struct_type.pretty();
-    return error_message.str().c_str();
+    computed_error_message = error_message.str();
+  }
+
+  const char *what() const noexcept override
+  {
+    return computed_error_message.c_str();
   }
 
 private:
   const struct_typet struct_type;
   const struct_union_typet::componentt component;
   const mp_integer byte_width;
 
+  std::string computed_error_message;
+
 };
 
 class non_constant_widtht : public flatten_byte_extract_exceptiont
@@ -93,20 +99,23 @@ class non_constant_widtht : public flatten_byte_extract_exceptiont
     : flatten_byte_extract_exceptiont("cannot unpack object of non-constant width"),
       src(src),
       max_bytes(max_bytes)
-  {
-  }
-
-  const char *what() const noexcept override
   {
     std::ostringstream error_message;
     error_message << runtime_error::what() << "\n";
     error_message << "array_type: " << src.pretty();
     error_message << "\nmax_bytes: " << max_bytes.pretty();
-    return error_message.str().c_str();
+    computed_error_message = error_message.str();
+  }
+
+  const char *what() const noexcept override
+  {
+    return computed_error_message.c_str();
   }
 private:
   exprt src;
   exprt max_bytes;
+
+  std::string computed_error_message;
 };
 
 class non_const_byte_extraction_sizet : public flatten_byte_extract_exceptiont
@@ -117,18 +126,21 @@ class non_const_byte_extraction_sizet : public flatten_byte_extract_exceptiont
     "byte_extract flatting with non-constant size"),
       unpack_expr(unpack_expr)
   {
+    std::ostringstream error_message;
+    error_message << runtime_error::what() << "\n";
+    error_message << "unpack_expr: " << unpack_expr.pretty();
+    computed_error_message = error_message.str();
   }
 
   const char *what() const noexcept override
   {
-    std::ostringstream error_message;
-    error_message << runtime_error::what() << "\n";
-    error_message << "unpack_expr: " << unpack_expr.pretty();
-    return error_message.str().c_str();
+    return computed_error_message.c_str();
   }
 
 private:
   const byte_extract_exprt unpack_expr;
+
+  std::string computed_error_message;
 };
 
 #endif //CPROVER_SOLVERS_FLATTENING_FLATTEN_BYTE_EXTRACT_EXCEPTIONS_H