build: FAILED conformance/definitions/signal_h/20-1: build: FAILED: Compiler output: conformance/definitions/signal_h/20-1.c:13:8: error: incomplete definition of type 'struct sigstack' sp = t.ss_sp; ~^ conformance/definitions/signal_h/20-1.c:7:8: note: forward declaration of 'struct sigstack' struct sigstack this_type_should_exist, t; ^ conformance/definitions/signal_h/20-1.c:14:13: error: incomplete definition of type 'struct sigstack' onstack = t.ss_onstack; ~^ conformance/definitions/signal_h/20-1.c:7:8: note: forward declaration of 'struct sigstack' struct sigstack this_type_should_exist, t; ^ conformance/definitions/signal_h/20-1.c:7:17: error: tentative definition has type 'struct sigstack' that is never completed struct sigstack this_type_should_exist, t; ^ conformance/definitions/signal_h/20-1.c:7:8: note: forward declaration of 'struct sigstack' struct sigstack this_type_should_exist, t; ^ conformance/definitions/signal_h/20-1.c:7:41: error: tentative definition has type 'struct sigstack' that is never completed struct sigstack this_type_should_exist, t; ^ conformance/definitions/signal_h/20-1.c:7:8: note: forward declaration of 'struct sigstack' struct sigstack this_type_should_exist, t; ^ 4 errors generated.