Re: exception when the field's value is NULL

Tommy Tang wrote:
> I have investigated the reason why it still failed in my computer, I used gdb 
> to debug the real reason and got the following information:
>
> 1. I set a breakpoint on the line :
>  unsigned int nMaxID = row["MaxID"],
>
> 2. step into it and get to MysqlRow::operator[](char const*) const (i="MaxID") 
> at row2.hh:19
> return (*this)[res->field_num(std::string(i)];  
>
> 3.step to MysqlResUse:;field_num(std::string const &) const  at result2.hh:12
>    if ( !_names ) _names = new FieldNames(this);
>  
> 4. next to get to the line 13:
>    return (*_names)[i];
>
> 5. next to get to MysqlRow::operator[](char const*) const (i="MaxID") at 
> row2.hh:20
>
> 6. step into to get to Mysql_ColData<const_string>::operator unsigned() const 
> at coldata1.hh:80
>     operator unsigned int() const { return conv((unsigned int)0); }
>
> 7.step into to get to unsigned 
> mysql_ColData<const_string>::conv<unsigned>(unsigned) const(dummy=0) at 
> coldata4.hh:12
>    std::string strbuf = buf;
>
> 8. next till to the line 18 of coldata4.hh
>     if (*end == '.'){
>
>   but I found here that the end ="NULL" and it doesn't meet if (*end !='0' && 
> end != NULL ), so then it went to line 23 : throw BadConversion(typeid(Type).name(), c_str(), end 
> - str, len );
>
> That is just the reason why I should catch the BadConversion, but I don't like to do it because it changes the code executing routine, what I expect is to when the filed is NULL, just set it to 0(for number filed), just like the mysql++ in Visual studio. I am surprised at this because it behaves different in Visual studio and gcc. 
The problem is that VC++ version is still 1.7.1 and that bug is fixed 
before 1.7.9.
A  solution is to change it manually in 1.7.1.

--

Sincerely,

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