Using MS Visual C++ 2005, Express Edition, the following snippet causes an
assertion failure due to a NULL pointer in the bowels of boost::format:
boost::format f( "test %1%\n" );
f % "";
I traced it down to boost/format/feed_args.hpp:
template
void mk_str( std::basic_string & res,
const Ch * beg,
typename std::basic_string::size_type size,
std::streamsize w,
const Ch fill_char,
std::ios_base::fmtflags f,
const Ch prefix_space, // 0 if no space-padding
bool center)
// applies centered/left/right padding to the string [beg, beg+size[
// Effects : the result is placed in res.
{
typedef typename std::basic_string::size_type
size_type;
res.resize(0);
if( ( w<=0 || static_cast(w) <=size)) {
// no need to pad.
res.reserve(size + !!prefix_space);
if(prefix_space)
res.append(1, prefix_space);
res.append(beg, size); <<--- crashes, because beg==NULL and
size==0
...
My suggested fix looks like this:
template
void mk_str( std::basic_string & res,
const Ch * beg,
typename std::basic_string::size_type size,
std::streamsize w,
const Ch fill_char,
std::ios_base::fmtflags f,
const Ch prefix_space, // 0 if no space-padding
bool center)
// applies centered/left/right padding to the string [beg, beg+size[
// Effects : the result is placed in res.
{
typedef typename std::basic_string::size_type
size_type;
res.resize(0);
if(size && ( w<=0 || static_cast(w) <=size)) {
// no need to pad.
res.reserve(size + !!prefix_space);
if(prefix_space)
res.append(1, prefix_space);
res.append(beg, size);
}
else {
std::streamsize
n=static_caststd::streamsize(w-size-!!prefix_space);
std::streamsize n_after = 0, n_before = 0;
res.reserve(w); // allocate once for the 2 inserts
if(center)
n_after = n/2, n_before = n - n_after;
else
if(f & std::ios_base::left)
n_after = n;
else
n_before = n;
// now make the res string :
if(n_before) res.append(n_before, fill_char);
if(prefix_space)
res.append(1, prefix_space);
if ( size )
res.append(beg, size);
if(n_after) res.append(n_after, fill_char);
}
} // -mk_str(..)
-- Early Ehlinger, President, ResPower, Inc.
