Re: Why do some code bases don't use exceptions?

Nick Keighley <>
Thu, 10 Dec 2009 01:32:35 -0800 (PST)
On 25 Nov, 16:28, (Richard) wrote:

peter koch <> spake the secret code
<> thusl=


[why exceptions?]

int func(parm p,std::string &result)
   std::string s;
   int error;

   result = func_1(parm,s);
   if (error != OK)
       return error;
   error = func_2(s);
   if (error != OK)
       return error;
   result = s;
   return OK;

instead of the much simpler

std::string func(parm)
   return func_2(func_1(parm));

This sort of code is profusely present in code that uses COM because
every method on a COM interface typically returns an HRESULT status
code that you should check.

it's the C way there's loads of stuff that works like that. Embedded
SQL, sockets, Win32. Every function returns an error code and you have
to check it.

Result db_update_box_title (Box_id id, const char *title)
     Box_data data;
     Db_conn connection = db_get_connection();
     if (connection == NULL)
          return E_CANT_CONNECT;

     db_read_box (id, &data);

     strcpy (data.title, title);

     db_write_box (id, &data);

Where CHECK_DB did something like

   if ((result = sql_error()) != SQL_OK)
       return result;

this was actually a concious effort to emulate exceptions. The code
could have been far nastier!

There are three ways I've seen people deal with such error codes:
- ignore them and pretend errors never happen (bad code)

oh yes! At least they have write extra code to ignore exceptions!

- inline handling as above (hard to read code)

- map HRESULTs to exceptions and handle them at the appropriate
  boundaries (throwing a C++ exception is undefined when implementing
  a COM object, so you have to catch and bubble out HRESULTs)

The latter is the approach I have been teaching for almost 10+ years
now and it dramatically simplifies writing and understanding such

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