Not sure exactly why this appeared after the release of Xcode 7.3, but we are no longer able to finish the configure phase due to a missing stdlib.h include in the conftests for OpenSSL and zlib. For example: ``` conftest.c:69:25: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration] RAND_add((void*)0,0,0); exit(0); ^ conftest.c:69:25: note: include the header <stdlib.h> or explicitly provide a declaration for 'exit' | void RAND_add(const void *buf, int num, double entropy); | int | main () | { | RAND_add((void*)0,0,0); exit(0); | ; | return 0; | } ``` When I edited configure.ac to add the include for both OpenSSL and zlib and re-ran autoconf, I was able to make the tests pass and finish configure. ``` TOR_SEARCH_LIBRARY(openssl, $tryssldir, [-lssl -lcrypto $TOR_LIB_GDI], [#include <openssl/rand.h>], [#include <stdlib.h>], [void RAND_add(const void *buf, int num, double entropy);], [RAND_add((void*)0,0,0); exit(0);], [], [/usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/athena /opt/openssl]) TOR_SEARCH_LIBRARY(zlib, $tryzlibdir, [-lz], [#include <zlib.h>], [#include <stdlib.h>], [const char * zlibVersion(void);], [zlibVersion(); exit(0);], [--with-zlib-dir], [/opt/zlib]) ``` We are also tracking this issue on GitHub here: https://github.com/ursachec/CPAProxy/issues/40 **Trac**: **Username**: chrisballinger