Add --force-output-type option

Author: dreifachstein

emcc.py

@@ -57,6 +57,8 @@
 
 JS_CONTAINING_SUFFIXES = ('js', 'html')
 
+EXPLICIT_OUTPUT_TYPES = ('js', 'html', 'bc')
+
 DEFERRED_REPONSE_FILES = ('EMTERPRETIFY_BLACKLIST', 'EMTERPRETIFY_WHITELIST')
 
 # Mapping of emcc opt levels to llvm opt levels. We use llvm opt level 3 in emcc opt
@@ -362,11 +364,6 @@ def uniquename(name):
   target = specified_target if specified_target is not None else 'a.out.js' # specified_target is the user-specified one, target is what we will generate
   target_basename = unsuffixed_basename(target)
 
-  if '.' in target:
-    final_suffix = target.split('.')[-1]
-  else:
-    final_suffix = ''
-
   if TEMP_DIR:
     temp_dir = TEMP_DIR
     if os.path.exists(temp_dir):
@@ -466,6 +463,7 @@ def log_time(name):
       # Specifies the line ending format to use for all generated text files.
       # Defaults to using the native EOL on each platform (\r\n on Windows, \n on Linux&OSX)
       output_eol = os.linesep
+      target_output_type = None
 
       def is_valid_abspath(path_name):
         # Any path that is underneath the emscripten repository root must be ok.
@@ -761,6 +759,14 @@ def detect_fixed_language_mode(args):
             exit(1)
           newargs[i] = ''
           newargs[i+1] = ''
+        elif newargs[i] == '--force-output-type':
+          if newargs[i+1] in EXPLICIT_OUTPUT_TYPES:
+            target_output_type = newargs[i+1]
+          else:
+            logging.error('Invalid value "' + newargs[i+1] + '" to --force-output-type')
+            exit(1)
+          newargs[i] = ''
+          newargs[i+1] = ''
 
       if should_exit:
         sys.exit(0)
@@ -913,6 +919,7 @@ def detect_fixed_language_mode(args):
 
       newargs = [arg for arg in newargs if arg is not '']
 
+      final_suffix = None
       # -c means do not link in gcc, and for us, the parallel is to not go all the way to JS, but stop at bitcode
       has_dash_c = '-c' in newargs
       if has_dash_c:
@@ -923,6 +930,15 @@ def detect_fixed_language_mode(args):
         final_suffix = 'eout' # not bitcode, not js; but just result from preprocessing stage of the input file
       if '-M' in newargs or '-MM' in newargs:
         final_suffix = 'mout' # not bitcode, not js; but just dependency rule of the input file
+
+      if final_suffix == None:
+        if target_output_type != None:
+          final_suffix = target_output_type
+        elif '.' in target:
+          final_suffix = target.split('.')[-1]
+        else:
+          final_suffix = ''
+
       final_ending = ('.' + final_suffix) if len(final_suffix) > 0 else ''
 
       # target is now finalized, can finalize other _target s