cmnLogger issue in conditional statement

[pkazanzides]

The following code does not produce the expected result:

if (condition)
   CMN_LOG_RUN_VERBOSE << "Some text" << std::endl;
else {
   // some more code
}

This appears to be due to the macro used to define CMN_LOG (note that CMN_LOG_RUN_VERBOSE just calls CMN_LOG with a specified lod):

 #define CMN_LOG(lod) \
  if (cmnLogger::GetMask() & cmnLogger::GetMaskFunction() & lod) \
    ((cmnLODOutputMultiplexer(cmnLogger::GetMultiplexer(), lod).Ref()) << cmnLogLevelToString(lod) << " ")

Simplifying the above, CMN_LOG(lod) essentially expands to the following:

if (filterTrue)
   cmnLODOutputMultiplexerRef << user_string << " "

Thus, the original code is compiled as follows, where the else is indented to better indicate the problem:

if (condition)
   if (filterTrue)
       cmnLODOutputMultiplexerRef << "Some text" << " " << std::endl;
   else {
      // some more code
   }

I believe the fix would be to put braces around the entire CMN_LOG macro, e.g.:

 #define CMN_LOG(lod) \
  { if (cmnLogger::GetMask() & cmnLogger::GetMaskFunction() & lod) \
    ((cmnLODOutputMultiplexer(cmnLogger::GetMultiplexer(), lod).Ref()) << cmnLogLevelToString(lod) << " ") }

[adeguet1]

Interestingly, gcc gives this warning:

/home/anton/catkin_ws/src/cisst-saw/cisst/cisstCommon/tests/cmnLogLoDTest.cpp:100:12: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses]

There were 4 of these in cisst, 2 in cisstMultiTask, 2 in cisstRobot.

Unfortunately adding braces in the macro doesn't solve the issue. The macro is used like this:

   CMN_LOG(level) << "some text" << std::end;

With the braces, this expends as:

  { if (condition) outputStream << } "some text" << std::endl;

which won't compile.

We can change the macro a bit to avoid the bug (I think?) but still triggers the gcc warning:

   // current logic
  #define log(level) \\
  if (needToLog(level)) outputStream <<

  // new logic
  #define log(level) \\
  if (!needToLog(level)) ; else outputStream <<

This is a bit better but programmers should still use braces to avoid the gcc warnings. Testing in branch bug-log: 2ddc476

I tested compilation and unit test for macro CMN_LOG on Windows/VS2013, MacOS clang, Linux gcc and it seems to work. I was expecting some warning because of the no-op before the else but all compilers seem fine with it.

[pkazanzides]

This fix seems fine.

[adeguet1]

In aae4bba:

• applied same logic CMN_LOG_CLASS macro.
• tracked most if (cond) CMN_LOG ... calls and added braces to avoid gcc warnings. Behavior is correct in any case but warnings can be alarming

Changes have been merged in devel branch.