Re: safe alternative to va_arg

From:
"Igor Tandetnik" <itandetnik@mvps.org>
Newsgroups:
microsoft.public.vc.language
Date:
Thu, 17 Apr 2008 08:18:27 -0400
Message-ID:
<eCMcmUIoIHA.1740@TK2MSFTNGP05.phx.gbl>
"Fabian" <Fabian@discussions.microsoft.com> wrote in message
news:B76FAB6E-A6A2-4354-9780-4E229F5A8758@microsoft.com

for my error handling I have a class with static method overloads to
print error messages (I will probably make this a bit more general
with some pattern later). But for the start it is enough to print
messages with different numbers of arguments. I don't want to write
endless overloads for different numbers of arguments. So my first
design looks like this:

static inline void PrintError(const char* source, const int&
numMsgParams, ...);

void ErrorHandler::PrintError(const char* source, const int&
numMsgParams, ...)
{
if (numMsgParams > 0)
{
va_list params;
va_start(params, numMsgParams);

char* addParam = NULL;

for (int i=0; i< numMsgParams; i++)
{
addParam = va_arg(params, char*);
cerr << addParam << ", ";
}

va_end(params);

Having to provide the number of arguments to the method call looks
pretty error-prone over maintenance time to me. Is there an
alternative?


If you are willing to limit yourself to some maximum number of
parameters, try something like this:

// Add as many parameters as needed.
void PrintError(const char* source, const char* param1 = 0, const char*
param2 = 0) {
  const char* params[] = {param1, param2};
  const int nParams = sizeof(params) / sizeof(params[0]);

  for (int i = 0; i < nParams; ++i) {
    if (params[i]) cout << params[i];
  }
}

--
With best wishes,
    Igor Tandetnik

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necessarily a good idea. It is hard to be sure where they are going to
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