Allow symbol resolution from the host process

Author: weliveindetail

CMakeLists.txt

@@ -93,6 +93,10 @@ target_compile_definitions(JitFromScratch PRIVATE ${LLVM_DEFINITIONS})
 target_link_libraries(JitFromScratch PRIVATE ${llvm_libs})
 target_compile_options(JitFromScratch PRIVATE ${rtti_flags})
 
+# Allow dlopen() to access exported symbols.
+# This will add linker flags like -Wl,--export-dynamic -rdynamic
+export_executable_symbols(JitFromScratch)
+
 function(dump_target_properties target property)
   get_target_property(values ${target} ${property})
   if(values)

JitFromScratch.cpp

@@ -13,6 +13,30 @@ JitFromScratch::JitFromScratch(ExitOnError ExitOnErr) {
   ExitOnErr(Builder.prepareForConstruction());
   TT = Builder.JTMB->getTargetTriple();
   LLJIT = ExitOnErr(Builder.create());
+
+  if (auto R = createHostProcessResolver(LLJIT->getDataLayout()))
+    LLJIT->getMainJITDylib().setGenerator(std::move(R));
+}
+
+JITDylib::GeneratorFunction
+JitFromScratch::createHostProcessResolver(DataLayout DL) {
+  char Prefix = DL.getGlobalPrefix();
+  Expected<JITDylib::GeneratorFunction> R =
+      DynamicLibrarySearchGenerator::GetForCurrentProcess(Prefix);
+
+  if (!R) {
+    LLJIT->getExecutionSession().reportError(R.takeError());
+    return nullptr;
+  }
+
+  if (!*R) {
+    LLJIT->getExecutionSession().reportError(createStringError(
+        inconvertibleErrorCode(),
+        "Generator function for host process symbols must not be null"));
+    return nullptr;
+  }
+
+  return *R;
 }
 
 Error JitFromScratch::submitModule(std::unique_ptr<Module> M,

JitFromScratch.h

@@ -46,5 +46,8 @@ class JitFromScratch {
   std::unique_ptr<llvm::orc::LLJIT> LLJIT;
   llvm::Triple TT;
 
+  llvm::orc::JITDylib::GeneratorFunction
+  createHostProcessResolver(llvm::DataLayout DL);
+
   llvm::Expected<llvm::JITTargetAddress> getFunctionAddr(llvm::StringRef Name);
 };