[PATCH] D93453: [flang][driver] Add support for `-I`

Wed Jan 6 05:08:25 PST 2021

awarzynski added a comment.

In D93453#2481720 <https://reviews.llvm.org/D93453#2481720>, @sscalpone wrote:

> Flang supports include files and module files.  The search path is used to look for both include files and module files.  The help text doesn't include info about module files.

Good point - the help message is inaccurate.  It comes from Options.td, which currently is shared with Clang: https://github.com/llvm/llvm-project/blob/main/clang/include/clang/Driver/Options.td#L650-L657. It documents Clang's internal implementation. IMO `Options.td` should not reveal internal implementation. In fact, that information is duplicated here: https://clang.llvm.org/docs/ClangCommandLineReference.html#include-path-management. I suggested a fix here: https://reviews.llvm.org/D94169.

> The help text refers to the -isystem option.  Is that implemented for flang, and if so, ought tests be added to make sure -I and -isystem co-exist as documented for flang?

`-isystem` is neither implemented nor planned in the near future for the new Flang driver [2]. Also, the updated `help` message won't contain any references to `-isystem`.

> Not that there's also a special include directory for intrinsic modules.  Intrinsic modules are treated specially, and right now, they are special by virtue of being in a special directory.  In the throwaway driver, the option is -intrinsic-module-directory.
>
> There's also the -module option to specify the directory into which newly created module files are written.   I don't recall if flang or other compilers generally add that directory to the search path as well.

Yea, we are aware of that. As proposed in [1] and [2]:

- `-intrinsic-module-directory` will be replaced with `-fintrinsic-modules-path`
- `-module` will be replaced with `-J/-module-dir`

There will be separate patches for these options.

[1] [flang-dev] RFC: new Flang driver options: https://lists.llvm.org/pipermail/flang-dev/2020-November/000588.html
[2] LLVM/flang new driver options: https://docs.google.com/spreadsheets/d/1JRe39lP_KhtkYxFEIvwrCFlE5v1Ofa_krOHI-XXXWPY/edit#gid=0

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