From e43a1cd76a35d5076b9f3b09909d7d8fccd8161c Mon Sep 17 00:00:00 2001
From: Antoine Coutant <antoine.coutant@smile.fr>
Date: Thu, 30 Nov 2023 11:10:20 +0100
Subject: [PATCH] clc: retrieve libclang path at runtime.

LLVM_LIB_DIR is a variable used for runtime compilations.
When cross compiling, LLVM_LIB_DIR must be set to the
libclang path on the target. So, this path should not
be retrieved during compilation but at runtime.

dladdr uses an address to search for a loaded library.
If a library is found, it returns information about it.
The path to the libclang library can therefore be
retrieved using one of its functions. This is useful
because we don't know the name of the libclang library
(libclang.so.X or libclang-cpp.so.X)

v2 (Karol): use clang::CompilerInvocation::CreateFromArgs for dladdr
v3 (Karol): follow symlinks to fix errors on debian

Fixes: e22491c8326 ("clc: fetch clang resource dir at runtime")
Signed-off-by: Antoine Coutant <antoine.coutant@smile.fr>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by (v1): Jesse Natalie <jenatali@microsoft.com>

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25568>
(cherry picked from commit 445aacb4217cbf5fb7be604c5484eb84c3c06497)
---
 .pick_status.json                |  2 +-
 src/compiler/clc/clc_helpers.cpp | 25 +++++++++++++++++++++----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index ca1d1d446b4..a16afeb865d 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -174,7 +174,7 @@
         "description": "clc: retrieve libclang path at runtime.",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "e22491c83265200f518e9fb4deff54e3c2823b68",
         "notes": null
diff --git a/src/compiler/clc/clc_helpers.cpp b/src/compiler/clc/clc_helpers.cpp
index 55287f22683..63026a806ee 100644
--- a/src/compiler/clc/clc_helpers.cpp
+++ b/src/compiler/clc/clc_helpers.cpp
@@ -23,6 +23,7 @@
 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 // OTHER DEALINGS IN THE SOFTWARE.
 
+#include <cstdlib>
 #include <filesystem>
 #include <sstream>
 #include <mutex>
@@ -57,6 +58,10 @@
 
 #include "spirv.h"
 
+#if DETECT_OS_UNIX
+#include <dlfcn.h>
+#endif
+
 #ifdef USE_STATIC_OPENCL_C_H
 #if LLVM_VERSION_MAJOR < 15
 #include "opencl-c.h.h"
@@ -876,12 +881,24 @@ clc_compile_to_llvm_module(LLVMContext &llvm_ctx,
 #endif
    }
 #else
+
+   Dl_info info;
+   if (dladdr((void *)clang::CompilerInvocation::CreateFromArgs, &info) == 0) {
+      clc_error(logger, "Couldn't find libclang path.\n");
+      return {};
+   }
+
+   char *clang_path = realpath(info.dli_fname, NULL);
+   if (clang_path == nullptr) {
+      clc_error(logger, "Couldn't find libclang path.\n");
+      return {};
+   }
+
    // GetResourcePath is a way to retrive the actual libclang resource dir based on a given binary
-   // or library. The path doesn't even need to exist, we just have to put something in there,
-   // because we might have linked clang statically.
-   auto libclang_path = fs::path(LLVM_LIB_DIR) / "libclang.so";
+   // or library.
    auto clang_res_path =
-      fs::path(Driver::GetResourcesPath(libclang_path.string(), CLANG_RESOURCE_DIR)) / "include";
+      fs::path(Driver::GetResourcesPath(std::string(clang_path), CLANG_RESOURCE_DIR)) / "include";
+   free(clang_path);
 
    c->getHeaderSearchOpts().UseBuiltinIncludes = true;
    c->getHeaderSearchOpts().UseStandardSystemIncludes = true;