Shmem comms [NO MPI] target added. The dwf test runs and passes.

Not really shaken out to my satisfaction though as I want more tests done, so don't declare as working.
But committing my current while I try a few experimentals.

lib/Log.h

@@ -29,9 +29,15 @@ Author: Peter Boyle <paboyle@ph.ed.ac.uk>
     /*  END LEGAL */
 #ifndef GRID_LOG_H
 #define GRID_LOG_H
+
+#ifdef HAVE_EXECINFO_H
+#include <execinfo.h>
+#endif
+
 namespace Grid {
 
 // Dress the output; use std::chrono for time stamping via the StopWatch class
+int Rank(void); // used for early stage debug before library init
 
 
 class Logger {
@@ -89,5 +95,35 @@ extern GridLogger GridLogPerformance;
 extern GridLogger GridLogIterative  ;
 extern GridLogger GridLogIntegrator  ;
 
+
+#define _NBACKTRACE (256)
+extern void * Grid_backtrace_buffer[_NBACKTRACE];
+
+#ifdef HAVE_EXECINFO_H
+#define BACKTRACEFILE() {\
+    char string[20];					\
+    std::sprintf(string,"backtrace.%d",Rank());				\
+    std::FILE * fp = std::fopen(string,"w");				\
+    BACKTRACEFP(fp)\
+    std::fclose(fp);	    \
+}
+#define BACKTRACE() BACKTRACE(std::stdout) 
+#define BACKTRACEFP(fp) { \
+  int symbols    = backtrace        (Grid_backtrace_buffer,_NBACKTRACE);\
+  char **strings = backtrace_symbols(Grid_backtrace_buffer,symbols);\
+  for (int i = 0; i < symbols; i++){\
+    std::fprintf (fp,"BackTrace Strings: %d %s\n",i, strings[i]); std::fflush(fp); \
+  }\
+}
+#else 
+#define BACKTRACE() BACKTRACE(std::stdout);
+
+#define BACKTRACEFP(fp) { \
+  for (int i = 0; i < 4; i++){\
+    std::fprintf (fp,"BT %d %lx\n",i, __builtin_return_address(i); std::fflush(fp); \
+  }\
+}
+#endif
+
 }
 #endif