What does '#if _LFS64_LARGEFILE-0' mean to CPP?

What does #if _LFS64_LARGEFILE-0 mean to the C Preprocessor for g++? Is that a minus zero or is that part of the sym开发者_高级运维bol? If it is minus zero, how does that affect whether the #if is triggered?

That is a more robust version of:

#if _LFS64_LARGEFILE

i.e. that the code should be conditionally included if _LFS64_LARGEFILE has a true value.

Adding the - 0, prevents you from getting a warning (#if with no expression) when _LFS64_LARGEFILE is not defined.