Env Variable: AMREX_DEBUG

Introduce control of backtrace handling and exception throwing via
the environment variable `AMREX_DEBUG`.

This is very handly when running CI/CD and IDE workflows to quickly
debug a failing test without overwriting default init parameters.

Docs/sphinx_documentation/source/Debugging.rst

@@ -100,6 +100,14 @@ The following runtime options need to be set in order to prevent AMReX from catc
 
 This default behavior can also be modified by applications, see for example `this custom application initializer <https://github.com/Exawind/amr-wind/blob/84f81a990152f4f748c1ab0fa17c8c663e51df86/amr-wind/main.cpp#L21>`__.
 
+The above default can also be achieve by setting the environment variable ``AMREX_DEBUG``:
+
+.. highlight:: console
+
+::
+
+    export AMREX_DEBUG=1
+
 
 .. _sec:gpu:debugging:
 

Src/Base/AMReX.cpp

@@ -334,18 +334,32 @@ amrex::Initialize (int& argc, char**& argv, bool build_parm_parse,
                    std::ostream& a_osout, std::ostream& a_oserr,
                    ErrorHandler a_errhandler)
 {
+    // trying to use AMReX in a debugger?
+    char const *env_amrex_debug = std::getenv("AMREX_DEBUG");
+    bool amrex_debug = false;
+    if (env_amrex_debug != nullptr) {
+        std::string str_amrex_debug{env_amrex_debug};
+        for(auto& c : test) { c = tolower(c); }
+
+        if (str_amrex_debug == "1" || str_amrex_debug == "on" || str_amrex_debug == "true") {
+            amrex_debug = true;
+        }
+    }
+
     system::exename.clear();
 //    system::verbose = 0;
     system::regtest_reduction = false;
-    system::signal_handling = true;
+
+
+    system::signal_handling = !amrex_debug;
     system::handle_sigsegv = true;
     system::handle_sigterm = false;
     system::handle_sigint  = true;
     system::handle_sigabrt = true;
     system::handle_sigfpe  = true;
     system::handle_sigill  = true;
     system::call_addr2line = true;
-    system::throw_exception = false;
+    system::throw_exception = amrex_debug;
     system::osout = &a_osout;
     system::oserr = &a_oserr;
     system::error_handler = a_errhandler;