QNU Make Question: Append value on the command line to a predefined macro in the make file
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From: Rainer Weikusat on 28 Jan 2010 10:19 micropentium <anderswang(a)gmail.com> writes: > int main(void) > { > #ifdef FOO > printf("FOO!\n"); > #endif > #ifdef BAR > printf("BAR!\n"); > #endif > return 0; > > } > > and a Makefile may be like this: > CPPFLAGS=-DFOO > a.out:foo.o > gcc -o $@ $^ > %.o:%.c > gcc -c $< ${CPPFLAGS} > > if I make it and run a.out (I am on a GNU Make 3.81), the output is > FOO!. If I want to print out BAR! or FOO!BAR!, I could always append - > DBAR onto CPPFLAGS. [...] > Is this doable through command line arguments to make? One possibility would be (in the Makefile, untested) ifdef FOO CPPFLAGS := $(CPPFLAGS) -DFOO endif ifdef BAR CPPFLAGS := $(CPPFLAGS) -DBAR endif Afterwards, make BAR=1 should result in BAR, make FOO=1 in FOO and make BAR=1 FOO=1 in both.
From: Ralf Fassel on 28 Jan 2010 11:04
* micropentium <anderswang(a)gmail.com> | and a Makefile may be like this: | CPPFLAGS=-DFOO | a.out:foo.o | gcc -o $@ $^ | %.o:%.c | gcc -c $< ${CPPFLAGS} | | if I make it and run a.out (I am on a GNU Make 3.81), the output is | FOO!. If I want to print out BAR! or FOO!BAR!, I could always append - | DBAR onto CPPFLAGS. | | So, my question is: what if I want to append -DBAR on the command | line? A workaround is providing a separate variable for the user to set from the command line: CPPFLAGS=-DFOO ${CPPFLAGS_USER} Then the user can invoke make CPPFLAGS_USER=-DBAR or even make CPPFLAGS_USER=-DBAR CPPFLAGS="" make CPPFLAGS_USER="-DBAR -UFOO" to prevent/undo the -DFOO. R' |