[PATCH] D33529: Allow clients to specify search order of DynamicLibraries.

[Frederich Munch via Phabricator via llvm-commits]

marsupial updated this revision to Diff 100513.
marsupial added a comment.

Formatting.


https://reviews.llvm.org/D33529

Files:
  include/llvm/Support/DynamicLibrary.h
  lib/Support/DynamicLibrary.cpp


Index: lib/Support/DynamicLibrary.cpp
===================================================================
--- lib/Support/DynamicLibrary.cpp
+++ lib/Support/DynamicLibrary.cpp
@@ -74,18 +74,27 @@
   }
 
   void *Lookup(const char *Symbol) {
-    // Process handle gets first try.
+    // Iterate in reverse, so newer libraries/symbols override older.
+    for (auto &&I = Handles.rbegin(), E = Handles.rend(); I != E; ++I) {
+      if (void *Ptr = DLSym(*I, Symbol))
+        return Ptr;
+    }
+    return nullptr;
+  }
+
+  void *Lookup(const char *Symbol, DynamicLibrary::SearchOrdering Order) {
+    if (!Process || Order == DynamicLibrary::SO_LoadedFirst) {
+      if (void *Ptr = Lookup(Symbol))
+        return Ptr;
+    }
     if (Process) {
+      // Use OS facilities to search the current binary and all loaded libs.
       if (void *Ptr = DLSym(Process, Symbol))
         return Ptr;
-#ifndef NDEBUG
-      for (void *Handle : Handles)
-        assert(!DLSym(Handle, Symbol) && "Symbol exists in non process handle");
-#endif
-    } else {
-      // Iterate in reverse, so newer libraries/symbols override older.
-      for (auto &&I = Handles.rbegin(), E = Handles.rend(); I != E; ++I) {
-        if (void *Ptr = DLSym(*I, Symbol))
+
+      // Search any libs that might have been skipped because of RTLD_LOCAL.
+      if (Order == DynamicLibrary::SO_LoadedLast) {
+        if (void *Ptr = Lookup(Symbol))
           return Ptr;
       }
     }
@@ -113,6 +122,8 @@
 #endif
 
 char DynamicLibrary::Invalid;
+DynamicLibrary::SearchOrdering DynamicLibrary::SearchOrder =
+    DynamicLibrary::SO_Linker;
 
 namespace llvm {
 void *SearchForAddressOfSpecialSymbol(const char *SymbolName) {
@@ -170,7 +181,7 @@
 
     // Now search the libraries.
     if (OpenedHandles.isConstructed()) {
-      if (void *Ptr = OpenedHandles->Lookup(SymbolName))
+      if (void *Ptr = OpenedHandles->Lookup(SymbolName, SearchOrder))
         return Ptr;
     }
   }
Index: include/llvm/Support/DynamicLibrary.h
===================================================================
--- include/llvm/Support/DynamicLibrary.h
+++ include/llvm/Support/DynamicLibrary.h
@@ -88,6 +88,19 @@
       return !getPermanentLibrary(Filename, ErrMsg).isValid();
     }
 
+    enum SearchOrdering {
+      /// SO_Linker - Search as a call to dlsym(dlopen(NULL)) would when
+      /// DynamicLibrary::getPermanentLibrary(NULL) has been called or
+      /// search the list of explcitly loaded symbols if not.
+      SO_Linker,
+      /// SO_LoadedFirst - Search all loaded libraries then as SO_Linker would
+      SO_LoadedFirst,
+      /// SO_LoadedLast - Search as SO_Linker would, then loaded libraries.
+      /// Only usefull to search libraries with RTLD_LOCAL have been added.
+      SO_LoadedLast,
+    };
+    static SearchOrdering SearchOrder; // = SO_Linker
+
     /// This function will search through all previously loaded dynamic
     /// libraries for the symbol \p symbolName. If it is found, the address of
     /// that symbol is returned. If not, null is returned. Note that this will


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