| 1 | ================================ |
|---|
| 2 | Frequently Asked Questions (FAQ) |
|---|
| 3 | ================================ |
|---|
| 4 | |
|---|
| 5 | .. contents:: |
|---|
| 6 | :local: |
|---|
| 7 | |
|---|
| 8 | Driver |
|---|
| 9 | ====== |
|---|
| 10 | |
|---|
| 11 | I run ``clang -cc1 ...`` and get weird errors about missing headers |
|---|
| 12 | ------------------------------------------------------------------- |
|---|
| 13 | |
|---|
| 14 | Given this source file: |
|---|
| 15 | |
|---|
| 16 | .. code-block:: c |
|---|
| 17 | |
|---|
| 18 | #include <stdio.h> |
|---|
| 19 | |
|---|
| 20 | int main() { |
|---|
| 21 | printf("Hello world\n"); |
|---|
| 22 | } |
|---|
| 23 | |
|---|
| 24 | |
|---|
| 25 | If you run: |
|---|
| 26 | |
|---|
| 27 | .. code-block:: console |
|---|
| 28 | |
|---|
| 29 | $ clang -cc1 hello.c |
|---|
| 30 | hello.c:1:10: fatal error: 'stdio.h' file not found |
|---|
| 31 | #include <stdio.h> |
|---|
| 32 | ^ |
|---|
| 33 | 1 error generated. |
|---|
| 34 | |
|---|
| 35 | ``clang -cc1`` is the frontend, ``clang`` is the :doc:`driver |
|---|
| 36 | <DriverInternals>`. The driver invokes the frontend with options appropriate |
|---|
| 37 | for your system. To see these options, run: |
|---|
| 38 | |
|---|
| 39 | .. code-block:: console |
|---|
| 40 | |
|---|
| 41 | $ clang -### -c hello.c |
|---|
| 42 | |
|---|
| 43 | Some clang command line options are driver-only options, some are frontend-only |
|---|
| 44 | options. Frontend-only options are intended to be used only by clang developers. |
|---|
| 45 | Users should not run ``clang -cc1`` directly, because ``-cc1`` options are not |
|---|
| 46 | guaranteed to be stable. |
|---|
| 47 | |
|---|
| 48 | If you want to use a frontend-only option ("a ``-cc1`` option"), for example |
|---|
| 49 | ``-ast-dump``, then you need to take the ``clang -cc1`` line generated by the |
|---|
| 50 | driver and add the option you need. Alternatively, you can run |
|---|
| 51 | ``clang -Xclang <option> ...`` to force the driver pass ``<option>`` to |
|---|
| 52 | ``clang -cc1``. |
|---|
| 53 | |
|---|
| 54 | I get errors about some headers being missing (``stddef.h``, ``stdarg.h``) |
|---|
| 55 | -------------------------------------------------------------------------- |
|---|
| 56 | |
|---|
| 57 | Some header files (``stddef.h``, ``stdarg.h``, and others) are shipped with |
|---|
| 58 | Clang --- these are called builtin includes. Clang searches for them in a |
|---|
| 59 | directory relative to the location of the ``clang`` binary. If you moved the |
|---|
| 60 | ``clang`` binary, you need to move the builtin headers, too. |
|---|
| 61 | |
|---|
| 62 | More information can be found in the :ref:`libtooling_builtin_includes` |
|---|
| 63 | section. |
|---|
| 64 | |
|---|
| 65 | |
|---|