Adding a RAII class to promote an object containt a symbol to be dlopened with RTLD_GLOBAL

src/core/PlumedMain.cpp

@@ -1091,7 +1091,7 @@ void PlumedMain::update() {
   }
 }
 
-void PlumedMain::load(const std::string& fileName, const bool loadGlobal) {
+void PlumedMain::load(const std::string& fileName) {
   if(DLLoader::installed()) {
     std::string libName=fileName;
     size_t n=libName.find_last_of(".");
@@ -1118,7 +1118,7 @@ void PlumedMain::load(const std::string& fileName, const bool loadGlobal) {
       base="./"+base;
     }
     libName=base+"."+config::getSoExt();
-    void *p=dlloader.load(libName,loadGlobal);
+    void *p=dlloader.load(libName);
     if(!p) {
       plumed_error()<<"I cannot load library " << fileName << " " << dlloader.error();
     }

src/core/PlumedMain.h

@@ -368,7 +368,7 @@ class PlumedMain:
 /// Stop the run
   void exit(int c=0);
 /// Load a shared library
-  void load(const std::string&, bool=false);
+  void load(const std::string&);
 /// Get the suffix string
   const std::string & getSuffix()const;
 /// Set the suffix string

src/setup/Load.cpp

@@ -106,7 +106,6 @@ PLUMED_REGISTER_ACTION(Load,"LOAD")
 void Load::registerKeywords( Keywords& keys ) {
   ActionSetup::registerKeywords(keys);
   keys.add("compulsory","FILE","file to be loaded");
-  keys.addFlag("GLOBAL",false,"when selected the shared object is LOADed with RTLD_GLOBAL instead of RTLD_LOCAL");
 }
 
 Load::Load(const ActionOptions&ao):
@@ -115,10 +114,8 @@ Load::Load(const ActionOptions&ao):
 {
   std::string f;
   parse("FILE",f);
-  bool loadWithGlobal=false;
-  parseFlag("GLOBAL",loadWithGlobal);
   checkRead();
-  plumed.load(f,loadWithGlobal);
+  plumed.load(f);
 }
 
 }

src/tools/DLLoader.cpp

@@ -20,6 +20,7 @@
    along with plumed.  If not, see <http://www.gnu.org/licenses/>.
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
 #include "DLLoader.h"
+
 #include <cstdlib>
 
 #ifdef __PLUMED_HAS_DLOPEN
@@ -37,13 +38,9 @@ bool DLLoader::installed() {
 }
 
 
-void* DLLoader::load(const std::string&s, const bool useGlobal) {
+void* DLLoader::load(const std::string&s) {
 #ifdef __PLUMED_HAS_DLOPEN
-  void* p=nullptr;
-  if (useGlobal)
-    p=dlopen(s.c_str(),RTLD_NOW|RTLD_GLOBAL);
-  else
-    p=dlopen(s.c_str(),RTLD_NOW|RTLD_LOCAL);
+  void* p=dlopen(s.c_str(),RTLD_NOW|RTLD_LOCAL);
   if(!p) {
     lastError=dlerror();
   } else {
@@ -79,5 +76,41 @@ DLLoader::DLLoader() {
   // do nothing
 }
 
+DLLoader::EnsureGlobalDLOpen::EnsureGlobalDLOpen(const void *symbol) noexcept {
+#ifdef __PLUMED_HAS_DLOPEN
+#ifdef __PLUMED_HAS_DLADDR
+  Dl_info info;
+  // from the manual:
+  // If the address specified in addr could not be matched to a shared
+  //      object, then these functions return 0.  In this case, an error
+  //      message is not available via dlerror(3).
+  int zeroIsError=dladdr(symbol, &info);
+  if(zeroIsError!=0) {
+    //This "promotes" to GLOBAL the object with the symbol pointed by ptr
+    handle_ = dlopen(info.dli_fname, RTLD_GLOBAL | RTLD_NOW);
+  } else {
+    std::fprintf(stderr,
+                 "+++WARNING+++"
+                 "Failure in finding any object that contains the symbol %p.\n",
+                 symbol);
+
+  }
+#else
+  std::fprintf(stderr,
+               "+++WARNING+++"
+               "I can't use dladdr for promoting the library containing the symbol %p.\n"
+               "This system seems not to support dladdr",
+               symbol);
+#endif //__PLUMED_HAS_DLADDR
+#endif //__PLUMED_HAS_DLOPEN
+}
 
+DLLoader::EnsureGlobalDLOpen::~EnsureGlobalDLOpen() {
+#ifdef __PLUMED_HAS_DLOPEN
+  if (handle_) {
+    dlclose(handle_);
+  }
+#endif //__PLUMED_HAS_DLOPEN
 }
+
+} // namespace PLMD

src/tools/DLLoader.h

@@ -50,11 +50,24 @@ class DLLoader {
   /// Cleanup
   ~DLLoader();
   /// Load a library, returning its handle
-  void* load(const std::string&, bool=false);
+  void* load(const std::string&);
   /// Returns the last error in dynamic loader
   const std::string & error();
   /// Returns true if the dynamic loader is available (on some systems it may not).
   static bool installed();
+
+  /// RAII helper for promoting RTLD_LOCAL loaded objects to RTLD_GLOBAL
+  class EnsureGlobalDLOpen {
+    void* handle_=nullptr;
+  public:
+    /// makes sure that object defining ptr is globally available
+    explicit EnsureGlobalDLOpen(const void* symbol) noexcept;
+    /// dlclose the dlopened object
+    ~EnsureGlobalDLOpen();
+    ///Confevert a const reference to a
+    template<typename T> EnsureGlobalDLOpen(const T&p) noexcept
+      : EnsureGlobalDLOpen(reinterpret_cast<const void*>(p)) {}
+  };
 };
 
 } // namespace PLMD