Improve support for GCC dual ABI with LLVM/AX/Houdini builds

openvdb_ax/openvdb_ax/compiler/Compiler.cc

@@ -38,6 +38,12 @@
 #include <llvm/Target/TargetMachine.h>
 #include <llvm/Target/TargetOptions.h>
 
+// @note  We use the C implementation of llvm::sys::getDefaultTargetTriple(),
+//   LLVMGetDefaultTargetTriple(), as the C++ version returns a std::string
+//   which causes issues with GCCs dual ABI (whereby most LLVM installations
+//   are on the newer ABI and the VFX platform, i.e. Houdini, is on the old ABI).
+#include <llvm-c/TargetMachine.h>
+
 // @note  As of adding support for LLVM 5.0 we not longer explicitly
 // perform standard compiler passes (-std-compile-opts) based on the changes
 // to the opt binary in the llvm codebase (tools/opt.cpp). We also no
@@ -66,13 +72,13 @@ namespace
 /// @brief  Initialize a target machine for the host platform. Returns a nullptr
 ///         if a target could not be created.
 /// @note   This logic is based off the Kaleidoscope tutorial below with extensions
-///         for CPU and CPU featrue set targetting
+///         for CPU and CPU feature set targeting
 ///         https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl08.html
 inline std::unique_ptr<llvm::ExecutionEngine>
 initializeExecutionEngine(std::unique_ptr<llvm::Module> M, Logger& logger)
 {
     // This handles MARCH (i.e. we don't need to set it on the EngineBuilder)
-    M->setTargetTriple(llvm::sys::getDefaultTargetTriple());
+    M->setTargetTriple(LLVMGetDefaultTargetTriple());
     llvm::Module* module = M.get();
 
     // stringref->bool map of features->enabled

openvdb_ax/openvdb_ax/test/backend/util.h

@@ -11,6 +11,7 @@
 #include <llvm/IR/IRBuilder.h>
 #include <llvm/ExecutionEngine/ExecutionEngine.h>
 #include <llvm/Support/Host.h>
+#include <llvm-c/TargetMachine.h> // LLVMGetDefaultTargetTriple
 
 #include <memory>
 #include <string>
@@ -46,7 +47,7 @@ struct LLVMState
 
     inline std::unique_ptr<llvm::ExecutionEngine> EE()
     {
-        mModule->setTargetTriple(llvm::sys::getDefaultTargetTriple());
+        mModule->setTargetTriple(LLVMGetDefaultTargetTriple());
         llvm::StringMap<bool> HostFeatures;
         llvm::sys::getHostCPUFeatures(HostFeatures);
         std::vector<llvm::StringRef> features;

pendingchanges/llvm_dual_abi.txt

@@ -0,0 +1,4 @@
+OpenVDB AX:
+    - Improvements:
+        Improved build support for using both GCCs old/new ABI which makes it
+        easier to use AX with Houdini.