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Re: cpp seems not to include # line "file" output for empty files
> It appears that cpp is deciding that it doesn't have to generate the #
> line output if there is no output from the file. This makes sense for
> the intend use of these directives for telling the compiler what
> filename/line number a line of cpp output came from, but it badly
> hoses dependency generators and other programs that rely on this
> output for getting a list of files that cpp read. Such functionality
> is essential for writing portable dependency generators. I feel like
> I've read this in the ISO standard but I can't seem to find any
> documentation that firmly states that ISO requires this behavior.
> If you want dependency info from cpp, use the switches to tell it to
> give you dependency info.
Not portable.
> Also, if the file generates no output, then a.c really wasn't dependent
> on it.
Wrong -- see my example. a.c is most definitely dependent upon a.h.