Implicit rules cannot invoke other implicit rules

[DelilahHoare]

If an implicit rule has an input that does not yet exist but could be made by another implicit rule, it will be skipped.

all: test.a

%.a: %.b
	echo $< > $@

%.b:
	echo $* > $@

This test makefile will successfully create test.a when run by GNU make, but ckati will fail with No rule to make target 'test.a' due to the pattern being declined because test.b does not already exist.

[lberki]

Is this something required to build the Linux kernel?

[DelilahHoare]

Yes. Without this feature the build fails with No rule to make target 'arch/x86/entry/vdso/vdso-image-64.o'. The rule it should be using, $(obj)/vdso-image-%.c, takes $(obj)/vdso%.so as input, which should be built by the rule for $(obj)/%.so.

[Kamillaova]

Probably the same problem is reproduced with Makefile generated by auto* (tested on bash).

After running ckati --ninja on the bash source code (after ./configure), running ./ninja.sh fails with:
ninja: error: '.made', needed by 'all', missing and no known rule to make it

But running just ckati almost works, but still fails at some point:

gcc  -DPROGRAM='"bash"' -DCONF_HOSTTYPE='"aarch64"' -DCONF_OSTYPE='"darwin23.5.0"' -DCONF_MACHTYPE='"aarch64-apple-darwin23.5.0"' -DCONF_VENDOR='"apple"' -DLOCALEDIR='"/usr/local/share/locale"' -DPACKAGE='"bash"' -DSHELL -DHAVE_CONFIG_H -DMACOSX   -I.  -I. -I./include -I./lib -I./lib/intl -I/Users/user/bbbas/bash-5.3/lib/intl -Wno-parentheses -Wno-format-security   -g -O2 -c locale.c
rm -f findcmd.o
gcc  -DPROGRAM='"bash"' -DCONF_HOSTTYPE='"aarch64"' -DCONF_OSTYPE='"darwin23.5.0"' -DCONF_MACHTYPE='"aarch64-apple-darwin23.5.0"' -DCONF_VENDOR='"apple"' -DLOCALEDIR='"/usr/local/share/locale"' -DPACKAGE='"bash"' -DSHELL -DHAVE_CONFIG_H -DMACOSX   -I.  -I. -I./include -I./lib -I./lib/intl -I/Users/user/bbbas/bash-5.3/lib/intl -Wno-parentheses -Wno-format-security   -g -O2 -c findcmd.c
Makefile:122: kati doesn't support .SUFFIXES with prerequisites
rm -f builtins.o
gcc -c   -DHAVE_CONFIG_H -DSHELL -I. -I..  -I.. -I../include -I../lib -I. -I../lib/intl -I/Users/user/bbbas/bash-5.3/lib/intl -Wno-parentheses -Wno-format-security -DMACOSX   -g -O2 builtins.c
rm -f alias.o
./mkbuiltins -D . alias.def
gcc -c   -DHAVE_CONFIG_H -DSHELL -I. -I..  -I.. -I../include -I../lib -I. -I../lib/intl -I/Users/user/bbbas/bash-5.3/lib/intl -Wno-parentheses -Wno-format-security -DMACOSX   -g -O2 .c || ( rm -f .c ; exit 1 )
*** [alias.o] Error 1
clang: error: no such file or directory: '.c'
clang: error: no input files
*** [builtins/libbuiltins.a] Error 1

I'm not sure if this is the same problem, but it looks like it.