[jira] [Created] (THRIFT-5272) printTo does not properly handle i8 datatypes

["Jeroen van Oosten (Jira)" <ji...@apache.org>]

Jeroen van Oosten created THRIFT-5272:
-----------------------------------------

             Summary: printTo does not properly handle i8 datatypes
                 Key: THRIFT-5272
                 URL: https://issues.apache.org/jira/browse/THRIFT-5272
             Project: Thrift
          Issue Type: Bug
          Components: C++ - Library
    Affects Versions: 0.13.0
         Environment: MSVC 2019 *and* Linux gcc 10.1.0
            Reporter: Jeroen van Oosten
         Attachments: TToString.h.patch

We have defined a datastructure with an i8 type in it, like so:
{code:java}
struct Meta
{
  1: i8 channel,
  2: i32 sequence
}
{code}
For debugging / logging purposes we are printing the information with Meta:: printTo, however the otuput is a bit odd. For example, we see this when the channel number is 0:

Meta(channel= , sequence=5)

I would expect to see "channel=0", just like all other integer types.

 

Further investigation shows that at the empty space after "channel=" there is in fact a null byte. And if I change 'channel' to 65, I get a "channel=A". Clearly the ASCII value is being dumped, not the integer value.

 

I have traced down the problem to TToString.h, line 34. The template function "to_string" there in combination with ostringstream does something weird when the input is a int8_t, which corresponds to a 'char' of course.

 

The fix is to add a specialization of that template for int8_t:
{code:java}
inline std::string my_string(const int8_t& t) {
  std::ostringstream o;
  o << static_cast<int>(t);
  return o.str();
}  

{code}
For your information: std::to_string *does* produce the expected result.



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