On Mon, Apr 29, 2002 at 09:32:15AM +1000, Ken Foskey wrote:
> gcc has an option -M or -MM (RTFM quoting from memory). SO you can
> create the dependencies and include them (I dont do this so read the
> make manual (it prints to over 300 pages) it has a sample on ho to do
> this and include it into the source.
>
> To do this you might do something like:
>
> yy.inc: yy.c
> gcc -MM > yy.inc
>
> -include yy.inc
>
> THere is no need to make depend because Make figure this out for
> itself. Pretty amazing really.
Here's how we do it. It's based on, but not quite the same as, the
example given in the make info pages. A few variables need to be
defined:
COMMON_INCLUDE_DIRS The list of directories to be searched for
header files, separated by spaces.
CPPFLAGS Compiler flags to be passed during
pre-processing (may be the same as $(CFLAGS)).
SOURCES The list of source files, separated by spaces.
Now here's the relevant bits of one makefile. It requires GNU make:
SHELL := /bin/sh
# VPATH is used by make to search for header files when examining
# dependencies. We need to use this because gcc doesn't include the
# directory names in dependencies generated with `-MM', and we don't
# have all our header files in one directory.
override VPATH := $(COMMON_INCLUDE_DIRS)
# and convert this list of directories into compiler directives
override includes := $(patsubst %,-I%,$(VPATH))
# create the list of object files from the list of source files
override objs := $(SOURCES:.c=.o)
##
##-----------------------------------------------------------------------------
##
#
# Pattern rules to automatically regenerate dependencies when a source file
# changes - no need to maintain lists of dependencies manually.
#
##
##-----------------------------------------------------------------------------
##
#
# Include the dependency files generated by these pattern rules - this
# gives make the complete dependency list for each source file. If a file
# is changed, the above pattern rules will force any .d files which depend
# upon it to be rebuilt. Make will first include all the dependency files,
# then remake any which require it, then re-read the new dependency file.
#
# The reading of dependency lists *before* building anything requires special
# care to be taken when a source or header file is deleted. First, remove
# all references to that file in all source files, and in this makefile. Then,
# make the target binary. Finally, delete the obsolete file. If you don't
# follow this procedure, you may get an error from make because it has found a
# dependency on the obsolete file, but it doesn't exist and make has no rule
# to make it. If that happens, delete the .d file which refers to the obsolete
# file, and restart make.
#
include $(objs:.o=.d)
#
# ~ is used as pattern separator in sed expressions because some files are
# located in subdirectories, so '/' may appear in the pattern itself
# $(notdir) and $(dir) are used to makes sure that the appropriate directory
# names appear in the targets of the rules - gcc doesn't include the
# directory name in the output of `gcc -MM'.
#
#
# .d from .c source
#
%.d: %.c
$(SHELL) -ec 'gcc -MM $(CPPFLAGS) $< \
| sed -e '\''s~\($(notdir $*)\)\.o[ :]*~$(dir $*)\1.o $@: ~g'\'' -e
'\''s~/\./~/~g'\'' > $@; \
[ -s $@ ] || rm -f $@'
#^^^^^^^^^^^ use tabs here, not spaces
Cheers,
John
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