Got this warning when compiling Python on Mac:

building '_scproxy' extension
gcc -Wno-unused-result -Wsign-compare -g -O0 -Wall -Wstrict-prototypes -Werror=declaration-after-statement -I./Include -I. -IInclude -I/usr/local/include -I/Users/sky/Code/python/cpython/Include -I/Users/sky/Code/python/cpython -c /Users/sky/Code/python/cpython/Modules/_scproxy.c -o build/temp.macosx-10.9-x86_64-3.6-pydebug/Users/sky/Code/python/cpython/Modules/_scproxy.o
/Users/sky/Code/python/cpython/Modules/_scproxy.c:74:10: warning: comparison of address of 'kSCPropNetProxiesExcludeSimpleHostnames' not equal to a null pointer is
      always true [-Wtautological-pointer-compare]
    if (&kSCPropNetProxiesExcludeSimpleHostnames != NULL) {
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~    ~~~~
/System/Library/Frameworks/SystemConfiguration.framework/Headers/SCSchemaDefinitions.h:3812:17: note: expanded from macro 'kSCPropNetProxiesExcludeSimpleHostnames'
          SC_SCHEMA_KV(kSCPropNetProxiesExcludeSimpleHostnames          \
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/System/Library/Frameworks/SystemConfiguration.framework/Headers/SCSchemaDefinitions.h:469:31: note: expanded from macro 'SC_SCHEMA_KV'
  #define SC_SCHEMA_KV(k,v,t)   k
                                ^
1 warning generated.
gcc -bundle -undefined dynamic_lookup build/temp.macosx-10.9-x86_64-3.6-pydebug/Users/sky/Code/python/cpython/Modules/_scproxy.o -L/usr/local/lib -o build/lib.macosx-10.9-x86_64-3.6-pydebug/_scproxy.cpython-36dm-darwin.so -framework SystemConfiguration -framework CoreFoundation

I am not sure though whether the patch is correct solution. But anyway....

The patch is not correct. 

You're probably building with a new enough version of OSX as the deployment target. _scproxy.c should recognise this and should only perform the != NULL test when the variable address might be NULL.

#if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_4
   if (if (&kSCPropNetProxiesExcludeSimpleHostnames != NULL) {
#end
      ....

#if MAC_OS_X_VERSION_MIN_REQUIRED <= MAC_OS_X_VERSION_10_4
   } else {
       ...
   }
#endif

And as the variable is available on OSX 10.4 we could just drop the test and assume it is available.

I'm closing this as out of date because the code the compiler warns about is no longer present in the master branch.