[tor-bugs] #20235 [Core Tor/Tor]: Configure misidentifies clock_gettime and getentropy on macOS Sierra/XCode8 when compiling for iOS 8

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#20235: Configure misidentifies clock_gettime and getentropy on macOS Sierra/XCode8
when compiling for iOS 8
-------------------------------------------------+-------------------------
 Reporter:  rainwolf                             |          Owner:
     Type:  defect                               |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.2.9.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.2.8.8
 Severity:  Normal                               |     Resolution:
 Keywords:  Sierra, XCode 8, clock_gettime,      |  Actual Points:
  getentropy, libSystem.dylib 028-backport osx   |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by nickm):

 Oh!  Hm.

 I tried making an example program as small as possible to still use
 getentropy():
 {{{
 #include <sys/types.h>
 #include <sys/random.h>
 #include <stdio.h>

 int main(int argc, char **argv)
 {
   unsigned x;
   if (getentropy(&x, sizeof(x)) < 0)
     perror("getentropy");
   else
     printf("%u\n", x);
   return 0;
 }
 }}}

 I tried compiling it in lots of different ways, but I couldn't find a way
 to tell gcc to ignore the presence of getentropy()....
 {{{
 % gcc -Wall -Wl,-no_weak_imports getentropy_test.c -o get
 % gcc -Wall -mmacosx-version-min=10.10 -Wl,-no_weak_imports
 getentropy_test.c -o get
 % ( export MACOSX_DEPLOYMENT_TARGET=10.10 ; gcc -Wall -mmacosx-version-
 min=10.10 -Wl,-no_weak_imports getentropy_test.c -o get )
 }}}

 I wonder if Apple messed up somehow and forgot to tag these APIs as 10.12
 only?  Or maybe I'm doing something wrong with the above.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20235#comment:4>
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