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Re: How to automatically update a automatically generated dependence fil

From: Philip Guenther
Subject: Re: How to automatically update a automatically generated dependence file?
Date: Fri, 24 Oct 2008 14:58:03 -0700

On Fri, Oct 24, 2008 at 1:45 PM, Peng Yu <address@hidden> wrote:
> I guess. I figure out how to use it. See below for the source code and
> the Makefile. After running make, I can change nothing3.hpp to
> nothing2.hpp. The make still runs after the modification.
> The first one  's/#.*//'  seems removes the comment, right? But would
> g++ -MM  generate comments?

If you have a new enough version of gcc, then instead of that complex
'sed' statement, you could just pass g++ the -MP option.  That alters
the -MM option so that it generates the desired stub targets.  Indeed,
you don't even need the separate MAKEDEPEND line: you can mix -MM and
-c and gcc/g++ will generate the dependency output *and* compile the
file in one pass.  Instead of defining your own rule for %.o:%.cpp,
just use the builtin one and update the COMPILE.cpp variable to
include the -MM and -MP options:

COMPILE.cpp += -MM -MP

That'll generate .d files, so change the include to

-include $(SRC:.cpp=.d)

That's it.

BTW, your makefile seems confused about whether you're doing C or C++,
as it does some stuff with $(CC) and $(COMPILE.c),  and other stuff
with g++.  If you're doing C++, then use $(CXX) and $(COMPILE.cpp).
That includes when linking, so that you can be sure the linker will be
told about the C++ library bits.

Philip Guenther

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