[PATCH] D92155: Load plugins when creating a CompilerInvocation.

[Yafei Liu via Phabricator via cfe-commits]

psionic12 added a comment.

In D92155#2450474 <https://reviews.llvm.org/D92155#2450474>, @nridge wrote:

> In D92155#2419549 <https://reviews.llvm.org/D92155#2419549>, @sammccall wrote:
>
>> In D92155#2419346 <https://reviews.llvm.org/D92155#2419346>, @psionic12 wrote:
>>
>>> Or, could you help to point out what's the difference between passing a plugin path through *clangd* startup command line and through clang flags?
>>
>> Sure. TL;DR is: clangd flags are configured by the user, user can be fully responsible for security/stability.
>> clang flags are configured by the project. If they're bad, we can e.g. give bad diagnostics, but can't crash or compromise security.
>>
>> More detail:
>>
>> In the simplest possible case, clangd is configured as follows:
>>
>> 1. user downloads clangd binary
>> 2. user installs an LSP plugin for their editor, and configures the plugin to use /usr/bin/clangd for C++ files. clangd starts when the editor does
>> 3. the build system for $PROJECT generates $PROJECT/compile_commands.json
>> 4. when the user opens $PROJECT/src/foo.cpp in the editor, it notifies clangd. clangd searches for $PROJECT/compile_commands.json, finds the clang arguments, and uses them to parse foo.cpp
>>
>> *clangd* command-line flags would be added explicitly by the user at step 2. We can reasonably ask the user to be aware/responsible for security/stability implications of doing this, including with their particular clangd version. We can also ask them to run `clangd --check` without the plugin flag to test whether the plugin is causing a stability problem.
>>
>> *clang* command-line flags are added implicitly in step 3. Or they could simply be checked into the repository - nothing ensures they were generated locally by the build system. The point is in typical usage they are not controlled by the user directly, and from a security perspective are not trusted (as safely opening files from untrusted repos is a reasonable expectation). So if we're loading plugins based on instructions in clang command-line flags, clangd bears most of the responsibility for making sure that's safe and correct (and I don't see a way to do that).
>
> Something just occurred to me: can't clangd arguments also be controlled by the untrusted repository by having a `.vscode/settings.json` file with specificed `"clangd.arguments"` checked in?

Yeah, there are too many ways to pass an argument without user's awareness, all the safety protections we talked about aren't help much, and I think this is not the clangd's problem, it exists in clang as well. So I think loading plugin codes guarded with CLANG_PLUGIN_SUPPORT on is enough, no more complicity protections should added.


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  https://reviews.llvm.org/D92155/new/

https://reviews.llvm.org/D92155