Support operating systems without some non-POSIX headers

The arpa/nameser.h, netinet/ip.h, and resolv.h headers are not crucial
to building LibreSSL. The netinet/ip.h header is used in nc(1) for
optional IPTOS_ features that can be ifdef'd on systems without support.

The endian.h header is the upcoming standard header and should be used
whenever available and correct. The machine/endian.h header is
non-standard and doesn't have to exist on POSIX systems.

Fix the check for getpagesize(3) not forward declaring the function,
such that CFLAGS with -Werror=implicit-function-declaration doesn't
cause the check to fail.

5 files changed, 8 insertions, 6 deletions

diff --git a/include/compat/arpa/nameser.h b/include/compat/arpa/nameser.h
index 0126a60..eff3b0d 100644
--- a/include/compat/arpa/nameser.h
+++ b/include/compat/arpa/nameser.h
@@ -4,7 +4,9 @@
  */
 
 #ifndef _WIN32
+#ifdef HAVE_ARPA_NAMESER_H
 #include_next <arpa/nameser.h>
+#endif
 #else
 #include <win32netcompat.h>
 
diff --git a/include/compat/machine/endian.h b/include/compat/machine/endian.h
index 4dcb60d..bb22f5b 100644
--- a/include/compat/machine/endian.h
+++ b/include/compat/machine/endian.h
@@ -21,7 +21,7 @@
 #define BYTE_ORDER BIG_ENDIAN
 #endif
 
-#elif defined(__linux__) || defined(__midipix__)
+#elif defined(HAVE_ENDIAN_H)
 #include <endian.h>
 
 #elif defined(__sun) || defined(_AIX) || defined(__hpux)
diff --git a/include/compat/netinet/ip.h b/include/compat/netinet/ip.h
index 6019f7d..29f17f3 100644
--- a/include/compat/netinet/ip.h
+++ b/include/compat/netinet/ip.h
@@ -8,7 +8,9 @@
 #endif
 
 #ifndef _WIN32
+#ifdef HAVE_NETINET_IP_H
 #include_next <netinet/ip.h>
+#endif
 #else
 #include <win32netcompat.h>
 #endif
diff --git a/include/compat/resolv.h b/include/compat/resolv.h
index 42dec07..b804460 100644
--- a/include/compat/resolv.h
+++ b/include/compat/resolv.h
@@ -12,7 +12,7 @@
 #else
 #include <../include/resolv.h>
 #endif
-#else
+#elif defined(HAVE_RESOLV_H)
 #include_next <resolv.h>
 #endif
 
diff --git a/m4/check-libc.m4 b/m4/check-libc.m4
index e511f6d..cca97c3 100644
--- a/m4/check-libc.m4
+++ b/m4/check-libc.m4
@@ -1,6 +1,7 @@
 AC_DEFUN([CHECK_LIBC_COMPAT], [
 # Check for libc headers
 AC_CHECK_HEADERS([err.h readpassphrase.h])
+AC_CHECK_HEADERS([arpa/nameser.h endian.h netinet/ip.h resolv.h])
 # Check for general libc functions
 AC_CHECK_FUNCS([asprintf freezero memmem])
 AC_CHECK_FUNCS([readpassphrase reallocarray recallocarray])
@@ -9,10 +10,7 @@ AC_CHECK_FUNCS([timegm _mkgmtime timespecsub])
 AC_CHECK_FUNCS([getprogname syslog syslog_r])
 AC_CACHE_CHECK([for getpagesize], ac_cv_func_getpagesize, [
         AC_LINK_IFELSE([AC_LANG_PROGRAM([[
-// Since Android NDK v16 getpagesize is defined as inline inside unistd.h
-#ifdef __ANDROID__
-#       include <unistd.h>
-#endif
+#include <unistd.h>
                 ]], [[
         getpagesize();
 ]])],