According to the gnu make documentation, if a rule generates multiple targets by a single invocation (for instance with a recipe executing a tool with multiple output files), you can use the '&:' rule syntax to tell make. I'm getting warnings when using this syntax, about target '&', however, when having multiple (but unique) targets in multiple rules. As if make mistakes the ampersand for a target name instead of being part of the target-prerequisite separator.
In my original project I've got two rules having multiple targets and a recipe generating those targets from a single statement/tool. The targets are unique for each of the two rules. I've created the following simple example to demonstrate the warning generated by make:
all: file_abbc
.PHONY: all clean
clean:
del /Q file_*
file_abbc: file_ab file_bc
copy file_ab+file_bc file_abbc
file_ab file_bc &: file_a file_b file_c
copy file_a+file_b file_ab
copy file_b+file_c file_bc
file_a file_b file_c &: content
copy content file_a
copy content file_b
copy content file_c
Warnings from running make on Windows on the above:
Makefile:17: warning: overriding recipe for target '&'
Makefile:13: warning: ignoring old recipe for target '&'
Why is make complaining about target '&' ?
You're using an old version of GNU make that doesn't understand &: rules, so just treats & as a file name. Use make --version to see which version you are running and upgrade if it is older that 4.3