automatically use libcxx when needed

emcc

@@ -469,8 +469,8 @@ try:
     # libcxx
     def create_libcxx():
       print >> sys.stderr, 'emcc: building libcxx for cache'
-      shared.Building.build_library('libcxx', EMSCRIPTEN_TEMP_DIR, EMSCRIPTEN_TEMP_DIR, ['libcxx.bc'], configure=None, copy_project=True)
-      return in_temp('libcxx.bc')
+      shared.Building.build_library('libcxx', shared.EMSCRIPTEN_TEMP_DIR, shared.EMSCRIPTEN_TEMP_DIR, ['libcxx.bc'], configure=None, copy_project=True, source_dir=shared.path_from_root('system', 'lib', 'libcxx'))
+      return os.path.join(shared.EMSCRIPTEN_TEMP_DIR, 'libcxx', 'libcxx.bc')
     def fix_libcxx():
       # libcxx probably needs sign correction. # If we are in mode 0, switch to 2. We will add our lines
       shared.Settings.CORRECT_SIGNS = 1
@@ -479,8 +479,8 @@ try:
     libcxx_symbols = filter(lambda symbol: symbol not in dlmalloc_symbols, libcxx_symbols)
     libcxx_symbols = set(libcxx_symbols)
 
-    for name, create, fix, library_symbols in [('dlmalloc', create_dlmalloc, fix_dlmalloc, dlmalloc_symbols)]:
-                                              #('libcxx',   create_libcxx,   fix_libcxx,   libcxx_symbols)]:
+    for name, create, fix, library_symbols in [('dlmalloc', create_dlmalloc, fix_dlmalloc, dlmalloc_symbols),
+                                               ('libcxx',   create_libcxx,   fix_libcxx,   libcxx_symbols)]:
       need = False
       has = False
       for input_file in input_files:

tests/hello_libcxx.cpp

@@ -0,0 +1,8 @@
+#include <iostream>
+
+int main()
+{
+  std::cout << "hello, world!" << std::endl;
+  return 0;
+}
+

tests/runner.py

@@ -6017,10 +6017,11 @@ elif 'sanity' in str(sys.argv):
         try_delete('a.out.js')
 
         # Building a file that *does* need dlmalloc *should* trigger cache generation, but only the first time
-        for filename, libname in [('hello_malloc.cpp', 'dlmalloc')]:
+        for filename, libname, otherlibname in [('hello_malloc.cpp', 'dlmalloc', 'libcxx'), ('hello_libcxx.cpp', 'libcxx', 'dlmalloc')]:
           for i in range(3):
             output = self.do([EMCC, path_from_root('tests', filename)])
             assert INCLUDING_MESSAGE.replace('X', libname) in output
+            assert INCLUDING_MESSAGE.replace('X', otherlibname) not in output
             assert (BUILDING_MESSAGE.replace('X', libname) in output) == (i == 0), 'Must only build the first time'
             self.assertContained('hello, world!', run_js('a.out.js'))
             assert os.path.exists(EMCC_CACHE)

tools/shared.py

@@ -378,20 +378,21 @@ class Building:
     Popen(args, stdout=stdout, stderr=stderr, env=env).communicate()[0]
 
   @staticmethod
-  def build_library(name, build_dir, output_dir, generated_libs, configure=['./configure'], configure_args=[], make=['make'], make_args=['-j', '2'], cache=None, cache_name=None, copy_project=False, env_init={}):
+  def build_library(name, build_dir, output_dir, generated_libs, configure=['./configure'], configure_args=[], make=['make'], make_args=['-j', '2'], cache=None, cache_name=None, copy_project=False, env_init={}, source_dir=None):
     ''' Build a library into a .bc file. We build the .bc file once and cache it for all our tests. (We cache in
         memory since the test directory is destroyed and recreated for each test. Note that we cache separately
         for different compilers).
         This cache is just during the test runner. There is a different concept of caching as well, see |Cache|. '''
 
     if type(generated_libs) is not list: generated_libs = [generated_libs]
+    if source_dir is None: source_dir = path_from_root('tests', name)
 
     temp_dir = build_dir
     if copy_project:
       project_dir = os.path.join(temp_dir, name)
       if os.path.exists(project_dir):
         shutil.rmtree(project_dir)
-      shutil.copytree(path_from_root('tests', name), project_dir) # Useful in debugging sometimes to comment this out, and two lines above
+      shutil.copytree(source_dir, project_dir) # Useful in debugging sometimes to comment this out, and two lines above
     else:
       project_dir = build_dir
     try:
@@ -489,15 +490,19 @@ class Building:
     class ret:
       defs = []
       undefs = []
+      commons = []
     for line in output.split('\n'):
       if len(line) == 0: continue
       status, symbol = filter(lambda seg: len(seg) > 0, line.split(' '))
       if status == 'U':
         ret.undefs.append(symbol)
-      else:
+      elif status != 'C':
         ret.defs.append(symbol)
+      else:
+        ret.commons.append(symbol)
     ret.defs = set(ret.defs)
     ret.undefs = set(ret.undefs)
+    ret.commons = set(ret.commons)
     return ret
 
   @staticmethod