[PATCH] D124815: [libclang] Fall back to getMainExecutable when dladdr fails

[Ayke via Phabricator via cfe-commits]

aykevl created this revision.
aykevl added reviewers: MaskRay, rsmith.
Herald added subscribers: StephenFan, arphaman.
Herald added a project: All.
aykevl requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

musl-libc doesn't support dladdr in statically linked binaries:

> Are you using static or dynamic linking? If static, dladdr is just a
> stub that always fails. It could be implemented to work under some
> conditions, but it would be highly dependent on what options you
> compile the binary with, since by default static binaries do not
> contain the bloat that would be needed to perform introspection.

Source: https://www.openwall.com/lists/musl/2013/01/15/25 (in response to a bug report).

Libclang unfortunately uses dladdr to find the ResourcesPath so will fail if it is linked statically on Alpine Linux. This patch fixes this issue by falling back to getMainExecutable if dladdr returns an error.

Reference: https://github.com/llvm/llvm-project/issues/40641#issuecomment-981011427


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124815

Files:
  clang/tools/libclang/CIndexer.cpp


Index: clang/tools/libclang/CIndexer.cpp
===================================================================
--- clang/tools/libclang/CIndexer.cpp
+++ clang/tools/libclang/CIndexer.cpp
@@ -125,13 +125,23 @@
 #elif defined(_AIX)
   getClangResourcesPathImplAIX(LibClangPath);
 #else
-  // This silly cast below avoids a C++ warning.
   Dl_info info;
-  if (dladdr((void *)(uintptr_t)clang_createTranslationUnit, &info) == 0)
-    llvm_unreachable("Call to dladdr() failed");
+  std::string Path;
+  // This silly cast below avoids a C++ warning.
+  if (dladdr((void *)(uintptr_t)clang_createTranslationUnit, &info) != 0) {
+    // We now have the CIndex directory, locate clang relative to it.
+    LibClangPath += info.dli_fname;
+  } else if (!(Path = llvm::sys::fs::getMainExecutable(nullptr, nullptr)).empty()) {
+    // If we can't get the path using dladdr, try to get the main executable
+    // path. This may be needed when we're statically linking libclang with
+    // musl libc, for example.
+    LibClangPath += Path;
+  } else {
+    // It's rather unlikely we end up here. But it could happen, so report an
+    // error instead of crashing.
+    llvm::report_fatal_error("Could not locate Clang resource path");
+  }
 
-  // We now have the CIndex directory, locate clang relative to it.
-  LibClangPath += info.dli_fname;
 #endif
 
   // Cache our result.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D124815.426553.patch
Type: text/x-patch
Size: 1372 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20220503/ac14b416/attachment.bin>