| // RUN: not FileCheck -check-prefix=FOO %s </dev/null 2>&1 | FileCheck -check-prefix=EMPTY-ERR %s | 
 | // RUN: not FileCheck -check-prefix=NOFOO %s </dev/null 2>&1 | FileCheck -check-prefix=EMPTY-ERR %s | 
 | // RUN: not FileCheck -check-prefix=FOO -allow-empty %s </dev/null 2>&1 | FileCheck -check-prefix=NO-EMPTY-ERR -check-prefix=NOT-FOUND %s | 
 | // RUN: FileCheck -check-prefix=NOFOO -allow-empty %s </dev/null 2>&1 | FileCheck -allow-empty -check-prefix=NO-EMPTY-ERR %s | 
 |  | 
 | ; FOO: foo | 
 | ; NOFOO-NOT: foo | 
 |  | 
 | ; EMPTY-ERR: FileCheck error: '-' is empty. | 
 | ; EMPTY-ERR-NEXT: FileCheck command line: {{.*}}FileCheck{{.*}}-check-prefix={{.*}}FOO {{.*}}check-empty.txt | 
 | ; NO-EMPTY-ERR-NOT: FileCheck error: '-' is empty. | 
 | ; NOT-FOUND: error: expected string not found in input |