configure: Add test for whether protoc matches protobuf

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

configure.ac

@@ -489,6 +489,24 @@ AS_IF([test "$enable_static_protobuf" = yes],
    AS_IF([test "$enable_static_libgcc" = yes],
      [AC_MSG_ERROR([--enable-static-libgcc requires --enable-static-protobuf])])])
 
+AC_MSG_CHECKING([whether protoc matches protobuf])
+cat > conftest.proto <<'EOF'
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+EOF
+AS_IF([$PROTOC --cpp_out=. conftest.proto],
+  [old_CPPFLAGS="$CPPFLAGS"
+   CPPFLAGS="$CPPFLAGS $protobuf_CFLAGS"
+   AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include "conftest.pb.h"]], [[]])],
+    [AC_MSG_RESULT([yes])],
+    [AC_MSG_RESULT([no])
+     cat conftest.err
+     AC_MSG_FAILURE([Could not build output generated by protoc ($PROTOC).
+Check that protoc matches the installed protobuf headers and libraries.])])
+   CPPFLAGS="$old_CPPFLAGS"],
+  [AC_MSG_RESULT([no])
+   AC_MSG_ERROR([Could not run protoc ($PROTOC).])])
+
 # Bash completion needs to ask where it goes if >= 2.0 is installed.
 AS_IF([test "$install_completion" != no],
   [PKG_CHECK_MODULES([BASH_COMPLETION], [bash-completion >= 2.0],