Compile an empty file.

$ export d="=========="
$ echo $d$d$d$d$d$d$d$d
================================================================================
$ touch empty.c
$ file empty.c
empty.c: empty
$ echo $d$d$d$d$d$d$d$d
================================================================================
$ clang -Wall -pedantic empty.c
empty.c:1:1: warning: ISO C requires a translation unit to contain at least one declaration [-Wempty-translation-unit]
1 warning generated.
Undefined symbols for architecture x86_64:
  "_main", referenced from:
     implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
$ echo $d$d$d$d$d$d$d$d
================================================================================
$ gcc-11 -Wall -pedantic empty.c
empty.c:2: warning: ISO C forbids an empty translation unit [-Wpedantic]
Undefined symbols for architecture x86_64:
  "_main", referenced from:
     implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
$ unset d
$