Additional debugging macros with low overhead are available, TRACE() and TRACEINST().
Both macros simulate a string stream, so they can be used like this:
TRACE() << "Reached.";
produces:
[LibSass] parse_value parser.cpp:1384 Reached.
TRACE()
logs function name, source filename, source file name to the standard error and the attached
stream to the standard error.
TRACEINST(obj)
logs object instance address, function name, source filename, source file name to the standard error and the attached stream to the standard error, for example:
TRACEINST(this) << "String_Constant created " << this;
produces:
[LibSass] 0x8031ba980:String_Constant ./ast.hpp:1371 String_Constant created (0,"auto")
The macros generate output only of LibSass_TRACE is set in the environment.