CODEWITHSUNDEEP
gnu-makeautotoolsautomake
John Frickson
John Frickson

Reputation: 189

I need a Makefile.am rule to update include file

I have a Makefile.am that looks something like this:

bin_PROGRAMS = prog

AM_CFLAGS = $(prog_CFLAGS)

prog_SOURCES = \
    data.h \
    src1.c \
    src2.c \
    ...
    src30.c

The data.h file is sometimes updated by a update_data.pl perl script depending on certain conditions. I tried adding this to the end of Makefile.am:

.PHONY: data.h
data.h:
    perl update_data.pl

but the script never runs. I'm sure I'm missing something simple, but I just can't figure it out.

Upvotes: 0

Views: 305

Answers (3)

John Frickson
John Frickson

Reputation: 189

This is how I finally got it to work. Using $(shell) may not be the best way, but it works.

bin_PROGRAMS = prog

AM_CFLAGS = $(prog_CFLAGS)

update_data := $(shell ./update_data.pl > /dev/tty)

prog_SOURCES = \
    data.h \
    src1.c \
    src2.c \
    ...
    src30.c

Upvotes: 0

ndim
ndim

Reputation: 37747

I am doing something similar for updating a header file with a few defines depending on the current git branch, HEAD commit, tree dirty state.

There might be a few uncaught corner cases, but it works for me. May it give you some inspiration.

CLEANFILES    += git-info.h
BUILT_SOURCES += git-info.h.stamp
git-info.h.stamp:
        echo "#ifndef GIT_INFO_H" > git-info.h.new
        echo "#define GIT_INFO_H" >> git-info.h.new
        echo "..." >> git-info.h.new
        echo "#endif" >> git-info.h.new
        if test -f git-info.h && cmp git-info.h.new git-info.h; then :; \
        else cat git-info.h.new > git-info.h; fi; \
        rm -f git-info.h.new

Notes:

  • The stamp file is never created, and thus this rule will always be executed on "make all" (not on "make my-program", though).

  • git-info.h is only ever touched if it has actually changed. This avoids rebuilds caused just by an updated timestamp of git-info.h without any changes to the content.

  • To reduce the rebuild effort when git-info.h has changed, I only include the generated git-info.h header from a single regular C my_program_SOURCES source file git-info.c which then defines a few global char foo[] = FOO; symbols which will then be linked to the final executable.

  • The git-info.o file will automatically depend on git-info.h, which will cause a rebuild when the header has changed.

Upvotes: 0

Diego Elio Pettenò
Diego Elio Pettenò

Reputation: 3240

Since you already have a data.h file, and it doesn't depend on anything, make thinks there's nothing to do to update it.

There's not really a good way to tell make to always recreate the file. You can have it depend on the update_data.pl file, if you want to regenerate it when you update the script. Or you can have it depend on the data file (as well as the script) if it's parsing and converting a data file.

But if your build is not hermetic, and the content depends on something make can't know about, there's no good way to solve your problem.

Upvotes: 1

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