Added check that plumed is not loaded in the global namespace

src/cltools/Benchmark.cpp

@@ -36,6 +36,9 @@
 #include <cstdio>
 #include <random>
 #include <algorithm>
+#if defined(__PLUMED_HAS_DLOPEN)
+#include <dlfcn.h>
+#endif
 
 namespace PLMD {
 namespace cltools {
@@ -213,6 +216,21 @@ int Benchmark::main(FILE* in, FILE*out,Communicator& pc) {
 
     plumed_assert(allplumed.size()>0 && allpaths.size()>0);
 
+#if defined(__PLUMED_HAS_DLOPEN)
+    if(std::any_of(allpaths.begin(),allpaths.end(),[](auto value) {return value != "this";})) {
+#if defined(__PLUMED_HAS_RTLD_DEFAULT)
+      void* handle=RTLD_DEFAULT;
+#else
+      handle=dlopen(NULL,RTLD_LOCAL);
+#endif
+      if(dlsym(handle,"plumed_plumedmain_create") || dlsym(handle,"plumedmain_create")) {
+        plumed_error()<<"It looks like libplumed is loaded in the global namespace, you cannot load a different version of the kernel\n"
+                      <<"Please make sure you use the plumed-runtime executable and that the env var PLUMED_LOAD_NAMESPACE is not set to GLOBAL";
+      }
+      if(handle) dlclose(handle);
+    }
+#endif
+
     if(allplumed.size()>1 && allpaths.size()>1 && allplumed.size() != allpaths.size()) {
       plumed_error() << "--kernel and --plumed should have either one element or the same number of elements";
     }