diff --git a/libc/tools/check-symbols-glibc.py b/libc/tools/check-symbols-glibc.py
index 8bcf7fc..0c7e28e 100755
--- a/libc/tools/check-symbols-glibc.py
+++ b/libc/tools/check-symbols-glibc.py
@@ -16,6 +16,14 @@
 if arch == 'aarch64':
   arch = 'arm64'
 
+def GetSymbolsFromTxt(txt_file):
+  symbols = set()
+  f = open(txt_file, 'r')
+  for line in f.read().splitlines():
+    symbols.add(line)
+  f.close()
+  return symbols
+
 def GetSymbolsFromSo(so_file):
   # Example readelf output:
   #   264: 0001623c     4 FUNC    GLOBAL DEFAULT    8 cabsf
@@ -75,6 +83,7 @@
 
 glibc = GetSymbolsFromSystemSo('libc.so.*', 'librt.so.*', 'libpthread.so.*', 'libresolv.so.*', 'libm.so.*')
 bionic = GetSymbolsFromAndroidSo('libc.so', 'libm.so')
+posix = GetSymbolsFromTxt(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'posix-2013.txt'))
 ndk_ignored = GetNdkIgnored()
 
 glibc = map(MangleGlibcNameToBionic, glibc)
@@ -190,6 +199,11 @@
     print symbol
 
   print
+  print 'in posix but not bionic:'
+  for symbol in sorted(posix.difference(bionic)):
+    print symbol
+
+  print
   print 'in bionic but not glibc:'
 
 allowed_stuff = (bsd_stuff | FORTIFY_stuff | linux_stuff | macro_stuff |
diff --git a/libc/tools/posix-2013.txt b/libc/tools/posix-2013.txt
new file mode 100644
index 0000000..6972c81
--- /dev/null
+++ b/libc/tools/posix-2013.txt
@@ -0,0 +1,1191 @@
+FD_CLR
+FD_ISSET
+FD_SET
+FD_ZERO
+_Exit
+_exit
+_longjmp
+_setjmp
+_tolower
+_toupper
+a64l
+abort
+abs
+accept
+access
+acosf
+acoshf
+acosh
+acoshl
+acos
+acosl
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+aio_error
+aio_fsync
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+aio_return
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+asctime_r
+asinf
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+atan
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+cfsetospeed
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+cimag
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+clock_getres
+clock_gettime
+clock
+clock_nanosleep
+clock_settime
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+close
+closelog
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+posix_spawnattr_getflags
+posix_spawnattr_getpgroup
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+posix_spawnattr_getschedpolicy
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+posix_spawnattr_getsigmask
+posix_spawnattr_init
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+posix_spawnattr_setpgroup
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+posix_spawnattr_setsigmask
+posix_spawn_file_actions_addclose
+posix_spawn_file_actions_adddup2
+posix_spawn_file_actions_addopen
+posix_spawn_file_actions_destroy
+posix_spawn_file_actions_init
+posix_spawn
+posix_spawnp
+posix_trace_attr_destroy
+posix_trace_attr_getclockres
+posix_trace_attr_getcreatetime
+posix_trace_attr_getgenversion
+posix_trace_attr_getinherited
+posix_trace_attr_getlogfullpolicy
+posix_trace_attr_getlogsize
+posix_trace_attr_getmaxdatasize
+posix_trace_attr_getmaxsystemeventsize
+posix_trace_attr_getmaxusereventsize
+posix_trace_attr_getname
+posix_trace_attr_getstreamfullpolicy
+posix_trace_attr_getstreamsize
+posix_trace_attr_init
+posix_trace_attr_setinherited
+posix_trace_attr_setlogfullpolicy
+posix_trace_attr_setlogsize
+posix_trace_attr_setmaxdatasize
+posix_trace_attr_setname
+posix_trace_attr_setstreamfullpolicy
+posix_trace_attr_setstreamsize
+posix_trace_clear
+posix_trace_close
+posix_trace_create
+posix_trace_create_withlog
+posix_trace_event
+posix_trace_eventid_equal
+posix_trace_eventid_get_name
+posix_trace_eventid_open
+posix_trace_eventset_add
+posix_trace_eventset_del
+posix_trace_eventset_empty
+posix_trace_eventset_fill
+posix_trace_eventset_ismember
+posix_trace_eventtypelist_getnext_id
+posix_trace_eventtypelist_rewind
+posix_trace_flush
+posix_trace_get_attr
+posix_trace_get_filter
+posix_trace_getnext_event
+posix_trace_get_status
+posix_trace_open
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+posix_trace_set_filter
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+posix_trace_start
+posix_trace_stop
+posix_trace_timedgetnext_event
+posix_trace_trid_eventid_open
+posix_trace_trygetnext_event
+posix_typed_mem_get_info
+posix_typed_mem_open
+powf
+pow
+powl
+pread
+printf
+pselect
+psiginfo
+psignal
+pthread_atfork
+pthread_attr_destroy
+pthread_attr_getdetachstate
+pthread_attr_getguardsize
+pthread_attr_getinheritsched
+pthread_attr_getschedparam
+pthread_attr_getschedpolicy
+pthread_attr_getscope
+pthread_attr_getstack
+pthread_attr_getstacksize
+pthread_attr_init
+pthread_attr_setdetachstate
+pthread_attr_setguardsize
+pthread_attr_setinheritsched
+pthread_attr_setschedparam
+pthread_attr_setschedpolicy
+pthread_attr_setscope
+pthread_attr_setstack
+pthread_attr_setstacksize
+pthread_barrierattr_destroy
+pthread_barrierattr_getpshared
+pthread_barrierattr_init
+pthread_barrierattr_setpshared
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+pthread_cleanup_push
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+pthread_condattr_getpshared
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+pthread_cond_broadcast
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+pthread_getcpuclockid
+pthread_getschedparam
+pthread_getspecific
+pthread_join
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+pthread_mutexattr_getpshared
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+pthread_mutex_timedlock
+pthread_mutex_trylock
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+pthread_once
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+wcsftime
+wcslen
+wcsncasecmp
+wcsncasecmp_l
+wcsncat
+wcsncmp
+wcsncpy
+wcsnlen
+wcsnrtombs
+wcspbrk
+wcsrchr
+wcsrtombs
+wcsspn
+wcsstr
+wcstod
+wcstof
+wcstoimax
+wcstok
+wcstold
+wcstol
+wcstoll
+wcstombs
+wcstoul
+wcstoull
+wcstoumax
+wcswidth
+wcsxfrm
+wcsxfrm_l
+wctob
+wctomb
+wctrans
+wctrans_l
+wctype
+wctype_l
+wcwidth
+wmemchr
+wmemcmp
+wmemcpy
+wmemmove
+wmemset
+wordexp
+wordfree
+wprintf
+write
+writev
+wscanf
+y0
+y1
+yn