Use the path of libmcwamp to dlopen libmcwamp_hsa, as static function (#1267)

* Use the path of libmcwamp to dlopen libmcwamp_hsa
* make fewer string copies
* CLAMP::library_path is now function get_library_path()
* get_library_path() now returns std::string&
* workaround bugs in std::call_once on Ubuntu 16.04

Change-Id: If1ac7cc9919016dfcc9b47939fac566a1c920bd3

Author: scchan

lib/mcwamp.cpp

@@ -90,6 +90,31 @@ namespace CLAMP {
 ////////////////////////////////////////////////////////////
 // Class declaration
 ////////////////////////////////////////////////////////////
+
+static std::string& get_library_path()
+{
+    static std::string library_path;
+    static std::once_flag once;
+    std::call_once(once, [] () {
+        // determine the search path for libmcwamp_hsa based on the
+        // path of this library
+        dl_iterate_phdr([](struct dl_phdr_info* info, size_t size, void* data) {
+          if (info->dlpi_name) {
+            std::string p(info->dlpi_name);
+            auto pos = p.find("libmcwamp.so");
+            if (pos != std::string::npos) {
+              p.erase(p.begin()+pos, p.end());
+              library_path = std::move(p);
+              return 1;
+            }
+          }
+          return 0;
+        } , nullptr);
+    });
+
+    return library_path;
+}
+
 /**
  * \brief Base class of platform detection
  */
@@ -132,7 +157,7 @@ class PlatformDetect {
  */
 class HSAPlatformDetect : public PlatformDetect {
 public:
-  HSAPlatformDetect() : PlatformDetect("HSA", LIB_NAME_WITH_VERSION("libmcwamp_hsa.so"), nullptr) {}
+  HSAPlatformDetect() : PlatformDetect("HSA", get_library_path() + LIB_NAME_WITH_VERSION("libmcwamp_hsa.so"), nullptr) {}
 };
 
 
@@ -146,7 +171,8 @@ static RuntimeImpl* LoadHSARuntime() {
   // load HSA C++AMP runtime
   if (mcwamp_verbose)
     std::cout << "Use HSA runtime" << std::endl;
-  runtimeImpl = new RuntimeImpl(LIB_NAME_WITH_VERSION("libmcwamp_hsa.so"));
+  std::string lib = get_library_path() + LIB_NAME_WITH_VERSION("libmcwamp_hsa.so");
+  runtimeImpl = new RuntimeImpl(lib.c_str());
   if (!runtimeImpl->m_RuntimeHandle) {
     std::cerr << "Can't load HSA runtime!" << std::endl;
     delete runtimeImpl;
@@ -162,7 +188,8 @@ static RuntimeImpl* LoadCPURuntime() {
   // load CPU runtime
   if (mcwamp_verbose)
     std::cout << "Use CPU runtime" << std::endl;
-  runtimeImpl = new RuntimeImpl(LIB_NAME_WITH_VERSION("libmcwamp_cpu.so"));
+  std::string lib = get_library_path() + LIB_NAME_WITH_VERSION("libmcwamp_cpu.so"); 
+  runtimeImpl = new RuntimeImpl(lib.c_str());
   if (!runtimeImpl->m_RuntimeHandle) {
     std::cerr << "Can't load CPU runtime!" << std::endl;
     delete runtimeImpl;
@@ -428,6 +455,7 @@ KalmarContext *getContext() {
 class KalmarBootstrap {
 public:
   KalmarBootstrap() {
+
     bool to_init = false;
     char* lazyinit_env = getenv("HCC_LAZYINIT");
     if (lazyinit_env != nullptr) {