[PATCH] D24933: Enable configuration files in clang

[Richard Smith via cfe-commits]

On 1 March 2017 at 02:50, Serge Pavlov via Phabricator <
reviews at reviews.llvm.org> wrote:

> sepavloff added a comment.
>
> Glad to know that someone is interested in this feature!
> Below is actual proposal.
>
> **Adding named configuration files to clang driver**
>
> A configuration file is a collection of driver options, which are inserted
> into command line before other options specified in the clang invocation.
> It groups related options together and allows specifying them in simpler,
> more flexible and less error prone way than just listing the options
> somewhere in build scripts. Configuration file may be thought as a "macro"
> that names an option set and is expanded when the driver is called.  This
> feature must be helpful when a user need to specify many options, cross
> compilation is likely to be such case.
>
> Configuration file can be specified by either of two methods:
>
> - by command line option `--config <config_file>`, or
> - by using special executable file names, such as `armv7l-clang`.
>
> If the option `--config` is used, its argument is treated as a path to
> configuration file if it contains a directory separator, otherwise the file
> is searched for in the set of directories described below. If option
> `--config` is absent and clang executable has name in the form
> `armv7l-clang`, driver will search for file `armv7l.cfg` in the same set of
> directories. Similar encoding is already used by clang to specify target.
>
> The set of directories where configuration files are searched for consists
> of at most three directories, checked in this order:
>
> - user directory (like `~/.llvm`),
> - system directory (like `/etc/llvm`),
> - the directory where clang executable resides.
>
> User and system directories are optional, they are reserved for
> distribution or SDK suppliers. By default they are absent, corresponding
> directories can be specified by cmake arguments
> `CLANG_CONFIG_FILE_SYSTEM_DIR` and `CLANG_CONFIG_FILE_USER_DIR`. The first
> found file is used.
>
> Format of configuration file is similar to file used in the construct
> `@file`, it is a set of options. Configuration file have advantage over
> this construct:
>
> - it is searched for in well-known places rather than in current directory,
>

This (and suppressing unused-argument warnings) might well be sufficient to
justify a different command-line syntax rather than @file...


> - it may contain comments, long options may be split between lines using
> trailing backslashes,
> - other files may be included by `@file` and they will be resolved
> relative to the including file,
>

... but I think we should just add these extensions to our @file handling,
and then use the exact same syntax and code to handle config files and
@file files. That is, the difference between @ and --config would be that
the latter looks in a different directory and suppresses "unused argument"
warnings, but they would otherwise be identical.

- the file may be encoded in executable name,
> - unused options from configuration file do not produce warnings.
>
>
> https://reviews.llvm.org/D24933
>
>
>
>
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