[tor-commits] [tor/release-0.2.8] Try to work around breakage in the OSX 10.12 SDK.

[nickm at torproject.org]

commit 16fcbd21c963a9a65bf55024680c8323c8b7175d
Author: Nick Mathewson <nickm at torproject.org>
Date:   Tue Nov 22 19:24:13 2016 -0500

    Try to work around breakage in the OSX 10.12 SDK.
    
    Apple is supposed to decorate their function declarations with
    macros to indicate which OSX version introduced them, so that you
    can tell the compiler that you want to build against certain
    versions of OSX.  But they forgot to do that for clock_gettime() and
    getentropy(), both of which they introduced in 10.12.
    
    This patch adds a kludge to the configure.ac script where, if we
    detect that we are targeting OSX 10.11 or earlier, we don't even probe
    to see if the two offending functions are present.
    
    Closes ticket 20235.
---
 changes/bug20235 |  4 ++++
 configure.ac     | 30 ++++++++++++++++++++++++++++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/changes/bug20235 b/changes/bug20235
new file mode 100644
index 0000000..54026a8
--- /dev/null
+++ b/changes/bug20235
@@ -0,0 +1,4 @@
+  o Minor features (compatibility):
+    - Work around a bug in the OSX 10.12 SDK that would prevent us
+      from successfully targetting earlier versions of OSX.
+      Resolves ticket 20235.
diff --git a/configure.ac b/configure.ac
index fb91f34..6647523 100644
--- a/configure.ac
+++ b/configure.ac
@@ -394,14 +394,12 @@ AC_CHECK_FUNCS(
         accept4 \
         backtrace \
         backtrace_symbols_fd \
-        clock_gettime \
 	eventfd \
 	explicit_bzero \
 	timingsafe_memcmp \
         flock \
         ftime \
         getaddrinfo \
-        getentropy \
         getifaddrs \
         getpass \
         getrlimit \
@@ -438,6 +436,34 @@ AC_CHECK_FUNCS(
 	_vscprintf
 )
 
+# Apple messed up when they added two functions functions in Sierra: they
+# forgot to decorate them with appropriate AVAILABLE_MAC_OS_VERSION
+# checks. So we should only probe for those functions if we are sure that we
+# are not targetting OSX 10.11 or earlier.
+AC_MSG_CHECKING([for a pre-Sierra OSX build target])
+AC_TRY_COMPILE([
+#ifdef __APPLE__
+#  include <AvailabilityMacros.h>
+#  ifndef MAC_OS_VERSION_10_12
+#    define MAC_OS_VERSION_10_12 101200
+#  endif
+#  if defined(MAC_OS_X_VERSION_MIN_REQUIRED)
+#    if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_VERSION_10_12
+#      error "Running on Mac OSX 10.11 or earlier"
+#    endif
+#  endif
+#endif
+], [],
+   [on_macos_pre_10_12=no ; AC_MSG_RESULT([no])],
+   [on_macos_pre_10_12=yes; AC_MSG_RESULT([yes])])
+
+if test "$on_macos_pre_10_12" = "no"; then
+  AC_CHECK_FUNCS(
+        clock_gettime \
+        getentropy \
+  )
+fi
+
 if test "$bwin32" != "true"; then
   AC_CHECK_HEADERS(pthread.h)
   AC_CHECK_FUNCS(pthread_create)