dynamically load getauxval so as to support older android devices

CMakeLists.txt

@@ -619,6 +619,10 @@ if (WIN32)
 	endif()
 endif()
 
+if(ANDROID)
+    target_link_libraries(torrent-rasterbar dl)
+endif()
+
 if(APPLE)
 	# for ip_notifier
 	target_link_libraries(torrent-rasterbar "-framework CoreFoundation" "-framework SystemConfiguration")

Jamfile

@@ -88,6 +88,11 @@ rule linking ( properties * )
 		}
 	}
 
+	if <target-os>android in $(properties)
+	{
+		result += <library>dl ;
+	}
+
 	if <target-os>beos in $(properties)
 	{
 		result += <library>netkit <library>gcc ;

configure.ac

@@ -89,6 +89,21 @@ AS_ECHO "Initializing Libtool:"
 LT_PREREQ([2.2.6])
 LT_INIT
 
+AS_IF([test "$SYS" = linux],[
+    AC_PREPROC_IFELSE([AC_LANG_PROGRAM(
+        [[#ifndef __ANDROID__
+         # error Not Android
+         #endif
+        ]],[[;]])
+    ],[
+      HAVE_ANDROID="1"
+      AC_MSG_RESULT([yes])
+    ],[
+      AC_MSG_RESULT([no])
+    ])
+])
+AM_CONDITIONAL(HAVE_ANDROID, test "${HAVE_ANDROID}" = "1")
+
 
 ###############################################################################
 # Checking for needed base libraries

src/Makefile.am

@@ -174,6 +174,10 @@ libtorrent_rasterbar_la_SOURCES = \
 libtorrent_rasterbar_la_LDFLAGS = -version-info $(INTERFACE_VERSION_INFO)
 libtorrent_rasterbar_la_LIBADD = @OPENSSL_LIBS@
 
+if HAVE_ANDROID
+libtorrent_rasterbar_la_LIBADD += -ldl
+endif
+
 AM_CPPFLAGS = -DTORRENT_BUILDING_LIBRARY -I$(top_srcdir)/include -I$(top_srcdir)/ed25519/src @DEBUGFLAGS@ @OPENSSL_INCLUDES@
 AM_CFLAGS = -I$(top_srcdir)/ed25519/src -std=c99
 

src/cpuid.cpp

@@ -55,8 +55,21 @@ POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 
-#if TORRENT_HAS_ARM && TORRENT_HAS_AUXV
+#if defined(TORRENT_ANDROID) && TORRENT_HAS_AUXV
+#include <dlfcn.h>
+namespace {
+unsigned long int helper_getauxval(unsigned long int type)
+{
+    using getauxval_t = unsigned long int(*)(unsigned long int);
+    getauxval_t pf_getauxval = reinterpret_cast<getauxval_t>(dlsym(RTLD_DEFAULT, "getauxval"));
+    if (pf_getauxval == nullptr)
+        return 0;
+    return pf_getauxval(type);
+}
+}
+#elif TORRENT_HAS_ARM && TORRENT_HAS_AUXV
 #include <sys/auxv.h>
+#define helper_getauxval getauxval
 #endif
 
 namespace libtorrent { namespace aux {
@@ -107,7 +120,7 @@ namespace libtorrent { namespace aux {
 #if TORRENT_HAS_ARM_NEON && TORRENT_HAS_AUXV
 #if defined __arm__
 		//return (getauxval(AT_HWCAP) & HWCAP_NEON);
-		return (getauxval(16) & (1 << 12));
+		return (helper_getauxval(16) & (1 << 12));
 #elif defined __aarch64__
 		//return (getauxval(AT_HWCAP) & HWCAP_ASIMD);
 		//return (getauxval(16) & (1 << 1));
@@ -126,10 +139,10 @@ namespace libtorrent { namespace aux {
 		return true;
 #elif defined __arm__
 		//return (getauxval(AT_HWCAP2) & HWCAP2_CRC32);
-		return (getauxval(26) & (1 << 4));
+		return (helper_getauxval(26) & (1 << 4));
 #elif defined __aarch64__
 		//return (getauxval(AT_HWCAP) & HWCAP_CRC32);
-		return (getauxval(16) & (1 << 7));
+		return (helper_getauxval(16) & (1 << 7));
 #endif
 #else
 		return false;