CLIon Doesn't Recognize All headers From Sysroot (e.g. dlfcn.h)

[auzhva]

Description of the bug:

In case of sys root used, non-c++ compiler headers are not supported. Such as "dlfcn.h". It shows red in CLion.

The build itself works ok. So for compiler and Bazel there is no issue with this header.

Which category does this issue belong to?

No response

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

1. Use toolchains_llvm
2. Include libl in your sysroot
3. Do #include <dlfcn.h> in your app

Which Intellij IDE are you using? Please provide the specific version.

2025.2.1

What programming languages and tools are you using? Please provide specific versions.

C++, toolchains_llvm 1.4.0, llvm 20.x

What Bazel plugin version are you using?

Bazel for CLion, 2025.08.04

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

No response

[LeFrosch]

Hi, thanks for bring this to our attention. Can you explain what you mean by including libl in your sysroot. Are you using a custom sysroot with the llvm toolchain? If yes, could you provide some snippets of how to set this toolchain up?

[auzhva]

Yes, we're using sysroot with the following packages:

"libc++1",
"libc++abi1",
"libgcc1",
"libgcc-8-dev",
"libunwind",
"libunwind-20-dev",
"libc6-dev",
"libc6",
"linux-libc-dev",
"libtsan0",
"libubsan1",
"libasan5",
"liblsan0",
"libgpgme-dev",
"libgpg-error-dev",
"libbtrfs-dev",

And then connecting it via:

llvm.toolchain(
    name = "hermetic_llvm",
    # ....
    cxx_standard = {"": "c++20"},
    llvm_versions = LLVM_VERSIONS,
    stdlib = {
        "linux-x86_64": "libc++",
        "linux-aarch64": "libc++",
    },
)
llvm.sysroot(
    name = "hermetic_llvm",
    label = "@ourcorp_sysroot_linux_x64//:sysroot",
    targets = ["linux-x86_64"],
)
llvm.sysroot(
    name = "hermetic_llvm",
    label = "@ourcorp_sysroot_linux_arm64//:sysroot",
    targets = ["linux-aarch64"],
)
use_repo(llvm, "hermetic_llvm")

So this allows us to build for both platforms using predictable sysroots.

The header dlfcn.h comes as part of it, same as other standard headers like string or string_view. But first one is red while the latter ones are not.

Here is a sysroot archive that we use for x86_64, if that helps.

You can find dlfcn.h under usr/include dir in the sysroot.

x86_64-linux-gnu-glibc2.28-sysroot-llvm-20-v2.tar.gz

[LeFrosch]

Yes thanks a lot, this looks really helpful :)

Could you run the following query in your bazel project to check if the include directory is listed there:

bazel cquery "@rules_cc//cc:current_cc_toolchain" --output=starlark --starlark:expr="providers(target)['@@_builtins//:common/cc/cc_toolchain_info.bzl%CcTool
chainInfo'].built_in_include_directories"

[auzhva]

It outputs:

["external/toolchains_llvm++llvm+hermetic_llvm_llvm/include/c++/v1", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/include/x86_64-unknown-linux-gnu/c++/v1", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/lib/clang/20.1.2/include", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/lib/clang/20.1.2/share", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/lib64/clang/20.1.2/include", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/lib/clang/20/include", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/lib/clang/20/share", "external/toolchains_llvm++llvm+hermetic_llvm_llvm/lib64/clang/20/include", "external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/include", "external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/usr/include", "external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/usr/local/include"]

And I guess the "external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/usr/include" is a right one.

I've checked that the file is there:

ls -la bazel-workspace/external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/usr/include | grep dlfcn
-rw-r--r--  1 xxx xxx   7018 Jul 31 13:10 dlfcn.h

[LeFrosch]

Follow up, and

bazel cquery "@rules_cc//cc:current_cc_toolchain" --output=starlark --starlark:expr="providers(target)['@@_builtins//:common/cc/cc_toolchain_info.bzl%CcToolchainInfo'].sysroot"

points to bazel-workspace/external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64?

[auzhva]

Points to external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/

(14:37:13) INFO: Invocation ID: 9122c414-c0d3-4c78-94c7-e12b0508b7a9
(14:37:13) INFO: Current date is 2025-09-04
(14:37:13) INFO: Analyzed target @@rules_cc+//cc:current_cc_toolchain (0 packages loaded, 0 targets configured).
(14:37:13) INFO: Found 1 target...
external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/
(14:37:13) INFO: Elapsed time: 0.259s, Critical Path: 0.00s
(14:37:13) INFO: 0 processes.
(14:37:13) INFO: Build completed successfully, 0 total actions

[LeFrosch]

Mmmh thanks, this all looks correct and should be working. One last thing, can you run the Show Compiler Info action in the source file with the broken include. It should list all the compiler flags that are discover by CLion in the beginning and all the header search paths at the bottom.

[auzhva]

There is one thing that is suspicious in this action. See in attached file.

What I see is:

--sysroot=/obfuscated/workspace/external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64

This is not correct. As /obfuscated/workspace is a path to my workspace. And "external" dir is not placed there, it's placed under convenience link, in my case "bazel-workspace".

So the correct path would be --sysroot=/obfuscated/workspace/bazel-workspace/external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64

Note that convenience link naming depends on a project name, but generally it's not correct to assume that the external/ dir is directly placed under workspace.

Referring to the previous answer, above I've shown that sysroot points to external/+nrm_llvm_sysroots+nrm_sysroot_linux_x64/. But it shall be noted, that this is relative to bazel output base (or convenience link), not to workspace itself.

Could that be the cause?

copmiler-info.txt