1 make: varmod-assign-shell.mk:21: warning: Command "echo output; (exit 13)" exited with status 13 2 Global: _ = # (empty) 3 Var_Parse: ${ASSIGNED::!=echo output; ${:U(exit 13)}} (eval-keep-dollar-and-undefined) 4 Evaluating modifier ${ASSIGNED::...} on value "previous" (eval-keep-dollar-and-undefined, regular) 5 Modifier part: "echo output; (exit 13)" 6 Capturing the output of command "echo output; (exit 13)" 7 make: varmod-assign-shell.mk:26: warning: Command "echo output; (exit 13)" exited with status 13 8 Result of ${ASSIGNED::!=echo output; ${:U(exit 13)}} is "" (eval-keep-dollar-and-undefined, regular) 9 Global: _ = # (empty) 10 Global: .MAKEFLAGS = -r -k -d v -d 11 Global: .MAKEFLAGS = -r -k -d v -d 0 12 DIRECT=output 13 ASSIGNED=previous 14 exit status 0 15