COMP: No Default

If we set a default to COMP, we cannot overwrite it with environment variables.
Since the examples and docs document this well, we can default to no
compiler and leave all the config to an environment/package manager.

This reduces surprises when using the regression tests.

Author: ax3l

docs/source/intro.rst

@@ -84,8 +84,8 @@ Using example-tests.ini as a template:
    #. Configure the build settings if necessary. The ``sourceTree`` variable
       determines the build system (C_Src => C++, AMReX =>
       standalone AMReX tests), while ``COMP`` determines the
-      compilers. The ``numMakeJobs`` and ``add_to_c_make_command`` parameters
-      allow for some additional control over the make command.
+      compilers (e.g., ``g++``). The ``numMakeJobs`` and ``add_to_c_make_command``
+      parameters allow for some additional control over the make command.
 
 #. Setting up the repositories:
 

suite.py

@@ -424,7 +424,7 @@ def __init__(self, args):
         self.MPIcommand = ""
         self.MPIhost = ""
 
-        self.COMP = "g++"
+        self.COMP = ""  # e.g., g++
 
         self.ftools = ["fcompare", "fboxinfo", "fsnapshot"]
         self.extra_tools = ""
@@ -1131,7 +1131,8 @@ def cmake_config( self, name, path, configOpts="",  install = 0, env = None):
         # Define enviroment
         ENV = {}
         ENV =  dict(os.environ) # Copy of current enviroment
-        ENV['CXX'] = self.COMP
+        if self.COMP:
+            ENV['CXX'] = self.COMP
 
         if env is not None: ENV.update(env)
 

test_util.py

@@ -36,7 +36,7 @@
 
   goUpLink = <1: add "Go UP" link at top of the web page >
 
-  COMP  = < name of C/C++ compiler >
+  COMP  = < name of C/C++ compiler, e.g., g++ >
 
   add_to_c_make_command = < any additional defines to add to the make invocation for C_Src AMReX >