issue #588, part 3

add check for the existence of inb() and outb()

CMakeLists.txt

@@ -564,8 +564,13 @@ if (NOT WIN32 AND NOT APPLE)
   CHECK_INCLUDE_FILE(linux/input.h LINUX_INPUT_FOUND)
   CHECK_INCLUDE_FILE(linux/kd.h LINUX_KD_FOUND)
   if (SYS_IO_FOUND)
-    list(APPEND DEPENDENCIES_DEFINES HAVE_SYS_IO)
-    message(STATUS "PC speaker output: outb()")
+    try_compile(HAVE_INOUTB ${CMAKE_BINARY_DIR}/check SOURCES ${CMAKE_SOURCE_DIR}/src/check/check_sysIO.c)
+    if (HAVE_INOUTB)
+      list(APPEND DEPENDENCIES_DEFINES HAVE_SYS_IO)
+      message(STATUS "PC speaker output: outb()")
+    else()
+      message(STATUS "sys/io.h found but inb()/outb() not present")
+    endif()
   endif()
   if (LINUX_INPUT_FOUND)
     list(APPEND DEPENDENCIES_DEFINES HAVE_LINUX_INPUT)

src/check/check_sysIO.c

@@ -0,0 +1,6 @@
+#include <sys/io.h>
+
+int main(int, char**) {
+  inb(0x61);
+  outb(0x00,0x61);
+}