Given this source file:
#include <stdio.h>
int main() {
printf("Hello world\n");
}
If you run:
$ clang -cc1 hello.c
hello.c:1:10: fatal error: 'stdio.h' file not found
#include <stdio.h>
^
1 error generated.
clang -cc1
is the frontend, clang
is the :doc:`driver
<DriverInternals>`. The driver invokes the frontend with options appropriate
for your system. To see these options, run:
$ clang -### -c hello.c
Some clang command line options are driver-only options, some are frontend-only
options. Frontend-only options are intended to be used only by clang developers.
Users should not run clang -cc1
directly, because -cc1
options are not
guaranteed to be stable.
If you want to use a frontend-only option ("a -cc1
option"), for example
-ast-dump
, then you need to take the clang -cc1
line generated by the
driver and add the option you need. Alternatively, you can run
clang -Xclang <option> ...
to force the driver pass <option>
to
clang -cc1
.
Some header files (stddef.h
, stdarg.h
, and others) are shipped with
Clang --- these are called builtin includes. Clang searches for them in a
directory relative to the location of the clang
binary. If you moved the
clang
binary, you need to move the builtin headers, too.
More information can be found in the :ref:`libtooling_builtin_includes` section.