[clang] 75d12e4 - [libclang] Fall back to getMainExecutable when dladdr fails

[Ayke van Laethem via cfe-commits]

Author: Ayke van Laethem
Date: 2022-05-29T13:40:43+02:00
New Revision: 75d12e49c729e65f77bfdfe65b16df8c39944d35

URL: https://github.com/llvm/llvm-project/commit/75d12e49c729e65f77bfdfe65b16df8c39944d35
DIFF: https://github.com/llvm/llvm-project/commit/75d12e49c729e65f77bfdfe65b16df8c39944d35.diff

LOG: [libclang] Fall back to getMainExecutable when dladdr fails

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

Differential Revision: https://reviews.llvm.org/D124815

Added: 
    

Modified: 
    clang/tools/libclang/CIndexer.cpp

Removed: 
    


################################################################################
diff  --git a/clang/tools/libclang/CIndexer.cpp b/clang/tools/libclang/CIndexer.cpp
index c7baab3a2c470..41f06a83553ad 100644
--- a/clang/tools/libclang/CIndexer.cpp
+++ b/clang/tools/libclang/CIndexer.cpp
@@ -125,13 +125,23 @@ const std::string &CIndexer::getClangResourcesPath() {
 #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.