move system libs calculation to its own file

2 files changed, 388 insertions, 381 deletions

diff --git a/emcc b/emcc
index 9f62d180..a77e2c4f 100755
--- a/emcc
+++ b/emcc
@@ -49,7 +49,7 @@ emcc can be influenced by a few environment variables:
 
 import os, sys, shutil, tempfile, subprocess, shlex, time, re, logging, json
 from subprocess import PIPE, STDOUT
-from tools import shared, jsrun
+from tools import shared, jsrun, system_libs
 from tools.shared import Compression, execute, suffix, unsuffixed, unsuffixed_basename, WINDOWS
 from tools.response_file import read_response_file
 
@@ -1408,389 +1408,12 @@ try:
 
   logging.debug('will generate JavaScript')
 
-  extra_files_to_link = []
-
   if not LEAVE_INPUTS_RAW and \
      not shared.Settings.BUILD_AS_SHARED_LIB and \
      not shared.Settings.SIDE_MODULE: # shared libraries/side modules link no C libraries, need them in parent
-
-    # Check if we need to include some libraries that we compile. (We implement libc ourselves in js, but
-    # compile a malloc implementation and stdlibc++.)
-
-    def read_symbols(path, exclude=None):
-      symbols = map(lambda line: line.strip().split(' ')[1], open(path).readlines())
-      if exclude:
-        symbols = filter(lambda symbol: symbol not in exclude, symbols)
-      return set(symbols)
-
-    lib_opts = ['-O2']
-
-    # XXX We also need to add libc symbols that use malloc, for example strdup. It's very rare to use just them and not
-    #     a normal malloc symbol (like free, after calling strdup), so we haven't hit this yet, but it is possible.
-    libc_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libc.symbols'))
-    libcextra_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libcextra.symbols'))
-    libcxx_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libcxx', 'symbols'), exclude=libc_symbols)
-    libcxxabi_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libcxxabi', 'symbols'), exclude=libc_symbols)
-
-    # XXX we should disable EMCC_DEBUG when building libs, just like in the relooper
-
-    def build_libc(lib_filename, files):
-      o_s = []
-      prev_cxx = os.environ.get('EMMAKEN_CXX')
-      if prev_cxx: os.environ['EMMAKEN_CXX'] = ''
-      musl_internal_includes = shared.path_from_root('system', 'lib', 'libc', 'musl', 'src', 'internal')
-      for src in files:
-        o = in_temp(os.path.basename(src) + '.o')
-        execute([shared.PYTHON, shared.EMCC, shared.path_from_root('system', 'lib', src), '-o', o, '-I', musl_internal_includes] + lib_opts, stdout=stdout, stderr=stderr)
-        o_s.append(o)
-      if prev_cxx: os.environ['EMMAKEN_CXX'] = prev_cxx
-      shared.Building.link(o_s, in_temp(lib_filename))
-      return in_temp(lib_filename)
-
-    def build_libcxx(src_dirname, lib_filename, files):
-      o_s = []
-      for src in files:
-        o = in_temp(src + '.o')
-        srcfile = shared.path_from_root(src_dirname, src)
-        execute([shared.PYTHON, shared.EMXX, srcfile, '-o', o, '-std=c++11'] + lib_opts, stdout=stdout, stderr=stderr)
-        o_s.append(o)
-      shared.Building.link(o_s, in_temp(lib_filename))
-      return in_temp(lib_filename)
-
-    # libc
-    def create_libc():
-      logging.debug(' building libc for cache')
-      libc_files = [
-        'dlmalloc.c',
-        os.path.join('libcxx', 'new.cpp'),
-      ]
-      musl_files = [
-        ['internal', [
-         'floatscan.c',
-         'shgetc.c',
-        ]],
-        ['math', [
-         'scalbn.c',
-         'scalbnl.c',
-        ]],
-        ['stdio', [
-         '__overflow.c',
-         '__toread.c',
-         '__towrite.c',
-         '__uflow.c',
-        ]],
-        ['stdlib', [
-         'atof.c',
-         'strtod.c',
-        ]],
-        ['string', [
-         'memcmp.c',
-         'strcasecmp.c',
-         'strcmp.c',
-         'strncasecmp.c',
-         'strncmp.c',
-        ]]
-      ]
-      for directory, sources in musl_files:
-        libc_files += [os.path.join('libc', 'musl', 'src', directory, source) for source in sources]
-      return build_libc('libc.bc', libc_files)
-
-    def apply_libc(need):
-      # libc needs some sign correction. # If we are in mode 0, switch to 2. We will add our lines
-      try:
-        if shared.Settings.CORRECT_SIGNS == 0: raise Exception('we need to change to 2')
-      except: # we fail if equal to 0 - so we need to switch to 2 - or if CORRECT_SIGNS is not even in Settings
-        shared.Settings.CORRECT_SIGNS = 2
-      if shared.Settings.CORRECT_SIGNS == 2:
-        shared.Settings.CORRECT_SIGNS_LINES = [shared.path_from_root('src', 'dlmalloc.c') + ':' + str(i+4) for i in [4816, 4191, 4246, 4199, 4205, 4235, 4227]]
-      # If we are in mode 1, we are correcting everything anyhow. If we are in mode 3, we will be corrected
-      # so all is well anyhow too.
-      return True
-
-    # libcextra
-    def create_libcextra():
-      logging.debug('building libcextra for cache')
-      musl_files = [
-         ['ctype', [
-          'iswalnum.c',
-          'iswalpha.c',
-          'iswblank.c',
-          'iswcntrl.c',
-          'iswctype.c',
-          'iswdigit.c',
-          'iswgraph.c',
-          'iswlower.c',
-          'iswprint.c',
-          'iswpunct.c',
-          'iswspace.c',
-          'iswupper.c',
-          'iswxdigit.c',
-          'towctrans.c',
-          'wcswidth.c',
-          'wctrans.c',
-          'wcwidth.c',
-         ]],
-         ['internal', [
-          'intscan.c',
-         ]],
-         ['legacy', [
-          'err.c',
-         ]],
-         ['locale', [
-          'iconv.c',
-          'iswalnum_l.c',
-          'iswalpha_l.c',
-          'iswblank_l.c',
-          'iswcntrl_l.c',
-          'iswctype_l.c',
-          'iswdigit_l.c',
-          'iswgraph_l.c',
-          'iswlower_l.c',
-          'iswprint_l.c',
-          'iswpunct_l.c',
-          'iswspace_l.c',
-          'iswupper_l.c',
-          'iswxdigit_l.c',
-          'strcoll.c',
-          'strcasecmp_l.c',
-          'strfmon.c',
-          'strncasecmp_l.c',
-          'strxfrm.c',
-          'towctrans_l.c',
-          'towlower_l.c',
-          'towupper_l.c',
-          'wcscoll.c',
-          'wcscoll_l.c',
-          'wcsxfrm.c',
-          'wcsxfrm_l.c',
-          'wctrans_l.c',
-          'wctype_l.c',
-         ]],
-         ['math', [
-          '__cos.c',
-          '__cosdf.c',
-          '__sin.c',
-          '__sindf.c',
-          'ilogb.c',
-          'ilogbf.c',
-          'ilogbl.c',
-          'ldexp.c',
-          'ldexpf.c',
-          'ldexpl.c',
-          'logb.c',
-          'logbf.c',
-          'logbl.c',
-          'lgamma.c',
-          'lgamma_r.c',
-          'lgammaf.c',
-          'lgammaf_r.c',
-          'lgammal.c',
-          'scalbnf.c',
-          'signgam.c',
-          'tgamma.c',
-          'tgammaf.c',
-          'tgammal.c'
-         ]],
-         ['misc', [
-          'getopt.c',
-          'getopt_long.c',
-         ]],
-         ['multibyte', [
-          'btowc.c',
-          'mblen.c',
-          'mbrlen.c',
-          'mbrtowc.c',
-          'mbsinit.c',
-          'mbsnrtowcs.c',
-          'mbsrtowcs.c',
-          'mbstowcs.c',
-          'mbtowc.c',
-          'wcrtomb.c',
-          'wcsnrtombs.c',
-          'wcsrtombs.c',
-          'wcstombs.c',
-          'wctob.c',
-          'wctomb.c',
-         ]],
-         ['regex', [
-          'fnmatch.c',
-          'regcomp.c',
-          'regerror.c',
-          'regexec.c',
-          'tre-mem.c',
-         ]],
-         ['stdio', [
-          'fwprintf.c',
-          'swprintf.c',
-          'vfwprintf.c',
-          'vswprintf.c',
-          'vwprintf.c',
-          'wprintf.c',
-          'fputwc.c',
-          'fputws.c',
-         ]],
-         ['stdlib', [
-           'ecvt.c',
-           'fcvt.c',
-           'gcvt.c',
-           'wcstod.c',
-           'wcstol.c',
-         ]],
-         ['string', [
-           'memccpy.c',
-           'memmem.c',
-           'mempcpy.c',
-           'memrchr.c',
-           'strcasestr.c',
-           'strchrnul.c',
-           'strlcat.c',
-           'strlcpy.c',
-           'strsep.c',
-           'strverscmp.c',
-           'wcpcpy.c',
-           'wcpncpy.c',
-           'wcscasecmp.c',
-           'wcscasecmp_l.c',
-           'wcscat.c',
-           'wcschr.c',
-           'wcscmp.c',
-           'wcscpy.c',
-           'wcscspn.c',
-           'wcsdup.c',
-           'wcslen.c',
-           'wcsncasecmp.c',
-           'wcsncasecmp_l.c',
-           'wcsncat.c',
-           'wcsncmp.c',
-           'wcsncpy.c',
-           'wcsnlen.c',
-           'wcspbrk.c',
-           'wcsrchr.c',
-           'wcsspn.c',
-           'wcsstr.c',
-           'wcstok.c',
-           'wcswcs.c',
-           'wmemchr.c',
-           'wmemcmp.c',
-           'wmemcpy.c',
-           'wmemmove.c',
-           'wmemset.c',
-         ]]
-      ]
-      libcextra_files = []
-      for directory, sources in musl_files:
-        libcextra_files += [os.path.join('libc', 'musl', 'src', directory, source) for source in sources]
-      return build_libc('libcextra.bc', libcextra_files)
-
-    # libcxx
-    def create_libcxx():
-      logging.debug('building libcxx for cache')
-      libcxx_files = [
-        'algorithm.cpp',
-        'condition_variable.cpp',
-        'future.cpp',
-        'iostream.cpp',
-        'memory.cpp',
-        'random.cpp',
-        'stdexcept.cpp',
-        'system_error.cpp',
-        'utility.cpp',
-        'bind.cpp',
-        'debug.cpp',
-        'hash.cpp',
-        'mutex.cpp',
-        'string.cpp',
-        'thread.cpp',
-        'valarray.cpp',
-        'chrono.cpp',
-        'exception.cpp',
-        'ios.cpp',
-        'locale.cpp',
-        'regex.cpp',
-        'strstream.cpp'
-      ]
-      return build_libcxx(os.path.join('system', 'lib', 'libcxx'), 'libcxx.bc', libcxx_files)
-
-    def apply_libcxx(need):
-      assert shared.Settings.QUANTUM_SIZE == 4, 'We do not support libc++ with QUANTUM_SIZE == 1'
-      # libcxx might need corrections, so turn them all on. TODO: check which are actually needed
-      shared.Settings.CORRECT_SIGNS = shared.Settings.CORRECT_OVERFLOWS = shared.Settings.CORRECT_ROUNDINGS = 1
-      #logging.info('using libcxx turns on CORRECT_* options')
-      return True
-
-    # libcxxabi - just for dynamic_cast for now
-    def create_libcxxabi():
-      logging.debug('building libcxxabi for cache')
-      libcxxabi_files = [
-        'typeinfo.cpp',
-        'private_typeinfo.cpp'
-      ]
-      return build_libcxx(os.path.join('system', 'lib', 'libcxxabi', 'src'), 'libcxxabi.bc', libcxxabi_files)
-
-    def apply_libcxxabi(need):
-      assert shared.Settings.QUANTUM_SIZE == 4, 'We do not support libc++abi with QUANTUM_SIZE == 1'
-      #logging.info('using libcxxabi, this may need CORRECT_* options')
-      #shared.Settings.CORRECT_SIGNS = shared.Settings.CORRECT_OVERFLOWS = shared.Settings.CORRECT_ROUNDINGS = 1
-      return True
-
-    # Settings this in the environment will avoid checking dependencies and make building big projects a little faster
-    # 1 means include everything; otherwise it can be the name of a lib (libcxx, etc.)
-    force = os.environ.get('EMCC_FORCE_STDLIBS')
-    force_all = force == '1'
-
-    # Scan symbols
-    symbolses = map(lambda temp_file: shared.Building.llvm_nm(temp_file), temp_files)
-
-    # Add in some hacks for js libraries. If a js lib depends on a symbol provided by a C library, it must be
-    # added to here, because our deps go only one way (each library here is checked, then we check the next
-    # in order - libcxx, libcxextra, etc. - and then we run the JS compiler and provide extra symbols from
-    # library*.js files. But we cannot then go back to the C libraries if a new dep was added!
-    # TODO: Move all __deps from src/library*.js to deps_info.json, and use that single source of info
-    #       both here and in the JS compiler.
-    deps_info = json.loads(open(shared.path_from_root('src', 'deps_info.json')).read())
-    def add_back_deps(need):
-      for ident, deps in deps_info.iteritems():
-        if ident in need.undefs:
-          for dep in deps:
-            need.undefs.add(dep)
-            shared.Settings.EXPORTED_FUNCTIONS.append('_' + dep)
-    for symbols in symbolses:
-      add_back_deps(symbols)
-
-    all_needed = set()
-    for symbols in symbolses:
-      all_needed.update(symbols.undefs)
-    for symbols in symbolses:
-      all_needed.difference_update(symbols.defs)
-
-    # Go over libraries to figure out which we must include
-    # If we have libcxx, we must force inclusion of libc, since libcxx uses new internally. Note: this is kind of hacky.
-    has = need = None
-    for name, create, apply_, library_symbols in [('libcxx',    create_libcxx,    apply_libcxx,    libcxx_symbols),
-                                                  ('libcextra', create_libcextra, lambda x: True,  libcextra_symbols),
-                                                  ('libcxxabi', create_libcxxabi, apply_libcxxabi, libcxxabi_symbols),
-                                                  ('libc',      create_libc,      apply_libc,      libc_symbols)]:
-      force_this = force_all or force == name
-      if not force_this:
-        need = set()
-        has = set()
-        for symbols in symbolses:
-          for library_symbol in library_symbols:
-            if library_symbol in symbols.undefs:
-              need.add(library_symbol)
-            if library_symbol in symbols.defs:
-              has.add(library_symbol)
-        for haz in has: # remove symbols that are supplied by another of the inputs
-          if haz in need:
-            need.remove(haz)
-        if shared.Settings.VERBOSE: logging.debug('considering %s: we need %s and have %s' % (name, str(need), str(has)))
-      if force_this or len(need) > 0:
-        force_all = True
-        if apply_(need):
-          # We need to build and link the library in
-          logging.debug('including %s' % name)
-          libfile = shared.Cache.get(name, create)
-          extra_files_to_link.append(libfile)
+    extra_files_to_link = system_libs.calculate(temp_files)
+  else:
+    extra_files_to_link = []
 
   log_time('calculate system libraries')
 
diff --git a/tools/system_libs.py b/tools/system_libs.py
new file mode 100644
index 00000000..42c9d67c
--- /dev/null
+++ b/tools/system_libs.py
@@ -0,0 +1,384 @@
+import os, json, logging
+import shared
+
+def calculate(temp_files):
+  # Check if we need to include some libraries that we compile. (We implement libc ourselves in js, but
+  # compile a malloc implementation and stdlibc++.)
+
+  def read_symbols(path, exclude=None):
+    symbols = map(lambda line: line.strip().split(' ')[1], open(path).readlines())
+    if exclude:
+      symbols = filter(lambda symbol: symbol not in exclude, symbols)
+    return set(symbols)
+
+  lib_opts = ['-O2']
+
+  # XXX We also need to add libc symbols that use malloc, for example strdup. It's very rare to use just them and not
+  #     a normal malloc symbol (like free, after calling strdup), so we haven't hit this yet, but it is possible.
+  libc_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libc.symbols'))
+  libcextra_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libcextra.symbols'))
+  libcxx_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libcxx', 'symbols'), exclude=libc_symbols)
+  libcxxabi_symbols = read_symbols(shared.path_from_root('system', 'lib', 'libcxxabi', 'symbols'), exclude=libc_symbols)
+
+  # XXX we should disable EMCC_DEBUG when building libs, just like in the relooper
+
+  def build_libc(lib_filename, files):
+    o_s = []
+    prev_cxx = os.environ.get('EMMAKEN_CXX')
+    if prev_cxx: os.environ['EMMAKEN_CXX'] = ''
+    musl_internal_includes = shared.path_from_root('system', 'lib', 'libc', 'musl', 'src', 'internal')
+    for src in files:
+      o = in_temp(os.path.basename(src) + '.o')
+      execute([shared.PYTHON, shared.EMCC, shared.path_from_root('system', 'lib', src), '-o', o, '-I', musl_internal_includes] + lib_opts, stdout=stdout, stderr=stderr)
+      o_s.append(o)
+    if prev_cxx: os.environ['EMMAKEN_CXX'] = prev_cxx
+    shared.Building.link(o_s, in_temp(lib_filename))
+    return in_temp(lib_filename)
+
+  def build_libcxx(src_dirname, lib_filename, files):
+    o_s = []
+    for src in files:
+      o = in_temp(src + '.o')
+      srcfile = shared.path_from_root(src_dirname, src)
+      execute([shared.PYTHON, shared.EMXX, srcfile, '-o', o, '-std=c++11'] + lib_opts, stdout=stdout, stderr=stderr)
+      o_s.append(o)
+    shared.Building.link(o_s, in_temp(lib_filename))
+    return in_temp(lib_filename)
+
+  # libc
+  def create_libc():
+    logging.debug(' building libc for cache')
+    libc_files = [
+      'dlmalloc.c',
+      os.path.join('libcxx', 'new.cpp'),
+    ]
+    musl_files = [
+      ['internal', [
+       'floatscan.c',
+       'shgetc.c',
+      ]],
+      ['math', [
+       'scalbn.c',
+       'scalbnl.c',
+      ]],
+      ['stdio', [
+       '__overflow.c',
+       '__toread.c',
+       '__towrite.c',
+       '__uflow.c',
+      ]],
+      ['stdlib', [
+       'atof.c',
+       'strtod.c',
+      ]],
+      ['string', [
+       'memcmp.c',
+       'strcasecmp.c',
+       'strcmp.c',
+       'strncasecmp.c',
+       'strncmp.c',
+      ]]
+    ]
+    for directory, sources in musl_files:
+      libc_files += [os.path.join('libc', 'musl', 'src', directory, source) for source in sources]
+    return build_libc('libc.bc', libc_files)
+
+  def apply_libc(need):
+    # libc needs some sign correction. # If we are in mode 0, switch to 2. We will add our lines
+    try:
+      if shared.Settings.CORRECT_SIGNS == 0: raise Exception('we need to change to 2')
+    except: # we fail if equal to 0 - so we need to switch to 2 - or if CORRECT_SIGNS is not even in Settings
+      shared.Settings.CORRECT_SIGNS = 2
+    if shared.Settings.CORRECT_SIGNS == 2:
+      shared.Settings.CORRECT_SIGNS_LINES = [shared.path_from_root('src', 'dlmalloc.c') + ':' + str(i+4) for i in [4816, 4191, 4246, 4199, 4205, 4235, 4227]]
+    # If we are in mode 1, we are correcting everything anyhow. If we are in mode 3, we will be corrected
+    # so all is well anyhow too.
+    return True
+
+  # libcextra
+  def create_libcextra():
+    logging.debug('building libcextra for cache')
+    musl_files = [
+       ['ctype', [
+        'iswalnum.c',
+        'iswalpha.c',
+        'iswblank.c',
+        'iswcntrl.c',
+        'iswctype.c',
+        'iswdigit.c',
+        'iswgraph.c',
+        'iswlower.c',
+        'iswprint.c',
+        'iswpunct.c',
+        'iswspace.c',
+        'iswupper.c',
+        'iswxdigit.c',
+        'towctrans.c',
+        'wcswidth.c',
+        'wctrans.c',
+        'wcwidth.c',
+       ]],
+       ['internal', [
+        'intscan.c',
+       ]],
+       ['legacy', [
+        'err.c',
+       ]],
+       ['locale', [
+        'iconv.c',
+        'iswalnum_l.c',
+        'iswalpha_l.c',
+        'iswblank_l.c',
+        'iswcntrl_l.c',
+        'iswctype_l.c',
+        'iswdigit_l.c',
+        'iswgraph_l.c',
+        'iswlower_l.c',
+        'iswprint_l.c',
+        'iswpunct_l.c',
+        'iswspace_l.c',
+        'iswupper_l.c',
+        'iswxdigit_l.c',
+        'strcoll.c',
+        'strcasecmp_l.c',
+        'strfmon.c',
+        'strncasecmp_l.c',
+        'strxfrm.c',
+        'towctrans_l.c',
+        'towlower_l.c',
+        'towupper_l.c',
+        'wcscoll.c',
+        'wcscoll_l.c',
+        'wcsxfrm.c',
+        'wcsxfrm_l.c',
+        'wctrans_l.c',
+        'wctype_l.c',
+       ]],
+       ['math', [
+        '__cos.c',
+        '__cosdf.c',
+        '__sin.c',
+        '__sindf.c',
+        'ilogb.c',
+        'ilogbf.c',
+        'ilogbl.c',
+        'ldexp.c',
+        'ldexpf.c',
+        'ldexpl.c',
+        'logb.c',
+        'logbf.c',
+        'logbl.c',
+        'lgamma.c',
+        'lgamma_r.c',
+        'lgammaf.c',
+        'lgammaf_r.c',
+        'lgammal.c',
+        'scalbnf.c',
+        'signgam.c',
+        'tgamma.c',
+        'tgammaf.c',
+        'tgammal.c'
+       ]],
+       ['misc', [
+        'getopt.c',
+        'getopt_long.c',
+       ]],
+       ['multibyte', [
+        'btowc.c',
+        'mblen.c',
+        'mbrlen.c',
+        'mbrtowc.c',
+        'mbsinit.c',
+        'mbsnrtowcs.c',
+        'mbsrtowcs.c',
+        'mbstowcs.c',
+        'mbtowc.c',
+        'wcrtomb.c',
+        'wcsnrtombs.c',
+        'wcsrtombs.c',
+        'wcstombs.c',
+        'wctob.c',
+        'wctomb.c',
+       ]],
+       ['regex', [
+        'fnmatch.c',
+        'regcomp.c',
+        'regerror.c',
+        'regexec.c',
+        'tre-mem.c',
+       ]],
+       ['stdio', [
+        'fwprintf.c',
+        'swprintf.c',
+        'vfwprintf.c',
+        'vswprintf.c',
+        'vwprintf.c',
+        'wprintf.c',
+        'fputwc.c',
+        'fputws.c',
+       ]],
+       ['stdlib', [
+         'ecvt.c',
+         'fcvt.c',
+         'gcvt.c',
+         'wcstod.c',
+         'wcstol.c',
+       ]],
+       ['string', [
+         'memccpy.c',
+         'memmem.c',
+         'mempcpy.c',
+         'memrchr.c',
+         'strcasestr.c',
+         'strchrnul.c',
+         'strlcat.c',
+         'strlcpy.c',
+         'strsep.c',
+         'strverscmp.c',
+         'wcpcpy.c',
+         'wcpncpy.c',
+         'wcscasecmp.c',
+         'wcscasecmp_l.c',
+         'wcscat.c',
+         'wcschr.c',
+         'wcscmp.c',
+         'wcscpy.c',
+         'wcscspn.c',
+         'wcsdup.c',
+         'wcslen.c',
+         'wcsncasecmp.c',
+         'wcsncasecmp_l.c',
+         'wcsncat.c',
+         'wcsncmp.c',
+         'wcsncpy.c',
+         'wcsnlen.c',
+         'wcspbrk.c',
+         'wcsrchr.c',
+         'wcsspn.c',
+         'wcsstr.c',
+         'wcstok.c',
+         'wcswcs.c',
+         'wmemchr.c',
+         'wmemcmp.c',
+         'wmemcpy.c',
+         'wmemmove.c',
+         'wmemset.c',
+       ]]
+    ]
+    libcextra_files = []
+    for directory, sources in musl_files:
+      libcextra_files += [os.path.join('libc', 'musl', 'src', directory, source) for source in sources]
+    return build_libc('libcextra.bc', libcextra_files)
+
+  # libcxx
+  def create_libcxx():
+    logging.debug('building libcxx for cache')
+    libcxx_files = [
+      'algorithm.cpp',
+      'condition_variable.cpp',
+      'future.cpp',
+      'iostream.cpp',
+      'memory.cpp',
+      'random.cpp',
+      'stdexcept.cpp',
+      'system_error.cpp',
+      'utility.cpp',
+      'bind.cpp',
+      'debug.cpp',
+      'hash.cpp',
+      'mutex.cpp',
+      'string.cpp',
+      'thread.cpp',
+      'valarray.cpp',
+      'chrono.cpp',
+      'exception.cpp',
+      'ios.cpp',
+      'locale.cpp',
+      'regex.cpp',
+      'strstream.cpp'
+    ]
+    return build_libcxx(os.path.join('system', 'lib', 'libcxx'), 'libcxx.bc', libcxx_files)
+
+  def apply_libcxx(need):
+    assert shared.Settings.QUANTUM_SIZE == 4, 'We do not support libc++ with QUANTUM_SIZE == 1'
+    # libcxx might need corrections, so turn them all on. TODO: check which are actually needed
+    shared.Settings.CORRECT_SIGNS = shared.Settings.CORRECT_OVERFLOWS = shared.Settings.CORRECT_ROUNDINGS = 1
+    #logging.info('using libcxx turns on CORRECT_* options')
+    return True
+
+  # libcxxabi - just for dynamic_cast for now
+  def create_libcxxabi():
+    logging.debug('building libcxxabi for cache')
+    libcxxabi_files = [
+      'typeinfo.cpp',
+      'private_typeinfo.cpp'
+    ]
+    return build_libcxx(os.path.join('system', 'lib', 'libcxxabi', 'src'), 'libcxxabi.bc', libcxxabi_files)
+
+  def apply_libcxxabi(need):
+    assert shared.Settings.QUANTUM_SIZE == 4, 'We do not support libc++abi with QUANTUM_SIZE == 1'
+    #logging.info('using libcxxabi, this may need CORRECT_* options')
+    #shared.Settings.CORRECT_SIGNS = shared.Settings.CORRECT_OVERFLOWS = shared.Settings.CORRECT_ROUNDINGS = 1
+    return True
+
+  # Settings this in the environment will avoid checking dependencies and make building big projects a little faster
+  # 1 means include everything; otherwise it can be the name of a lib (libcxx, etc.)
+  force = os.environ.get('EMCC_FORCE_STDLIBS')
+  force_all = force == '1'
+
+  # Scan symbols
+  symbolses = map(lambda temp_file: shared.Building.llvm_nm(temp_file), temp_files)
+
+  # Add in some hacks for js libraries. If a js lib depends on a symbol provided by a C library, it must be
+  # added to here, because our deps go only one way (each library here is checked, then we check the next
+  # in order - libcxx, libcxextra, etc. - and then we run the JS compiler and provide extra symbols from
+  # library*.js files. But we cannot then go back to the C libraries if a new dep was added!
+  # TODO: Move all __deps from src/library*.js to deps_info.json, and use that single source of info
+  #       both here and in the JS compiler.
+  deps_info = json.loads(open(shared.path_from_root('src', 'deps_info.json')).read())
+  def add_back_deps(need):
+    for ident, deps in deps_info.iteritems():
+      if ident in need.undefs:
+        for dep in deps:
+          need.undefs.add(dep)
+          shared.Settings.EXPORTED_FUNCTIONS.append('_' + dep)
+  for symbols in symbolses:
+    add_back_deps(symbols)
+
+  all_needed = set()
+  for symbols in symbolses:
+    all_needed.update(symbols.undefs)
+  for symbols in symbolses:
+    all_needed.difference_update(symbols.defs)
+
+  # Go over libraries to figure out which we must include
+  # If we have libcxx, we must force inclusion of libc, since libcxx uses new internally. Note: this is kind of hacky.
+  ret = []
+  has = need = None
+  for name, create, apply_, library_symbols in [('libcxx',    create_libcxx,    apply_libcxx,    libcxx_symbols),
+                                                ('libcextra', create_libcextra, lambda x: True,  libcextra_symbols),
+                                                ('libcxxabi', create_libcxxabi, apply_libcxxabi, libcxxabi_symbols),
+                                                ('libc',      create_libc,      apply_libc,      libc_symbols)]:
+    force_this = force_all or force == name
+    if not force_this:
+      need = set()
+      has = set()
+      for symbols in symbolses:
+        for library_symbol in library_symbols:
+          if library_symbol in symbols.undefs:
+            need.add(library_symbol)
+          if library_symbol in symbols.defs:
+            has.add(library_symbol)
+      for haz in has: # remove symbols that are supplied by another of the inputs
+        if haz in need:
+          need.remove(haz)
+      if shared.Settings.VERBOSE: logging.debug('considering %s: we need %s and have %s' % (name, str(need), str(has)))
+    if force_this or len(need) > 0:
+      force_all = True
+      if apply_(need):
+        # We need to build and link the library in
+        logging.debug('including %s' % name)
+        libfile = shared.Cache.get(name, create)
+        ret.append(libfile)
+  return ret
+