sd-common: add __const__

const is stronger than pure, see
https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
and
https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute.

(cherry picked from commit 955c51c087f1fb6d0b7a0091db943ad05ba3095e)

diff --git a/src/systemd/_sd-common.h b/src/systemd/_sd-common.h
index d4381d90f4a44eb7e232c5139376dc28d6a1ec22..1e1ce35418afc67fda88b3e143f3dcebc0b13c66 100644 (file)
--- a/src/systemd/_sd-common.h
+++ b/src/systemd/_sd-common.h
@@ -45,6 +45,10 @@ typedef void (*_sd_destroy_t)(void *userdata);
 #  define _sd_pure_ __attribute__((__pure__))
 #endif
 
+#ifndef _sd_const_
+#  define _sd_const_ __attribute__((__const__))
+#endif
+
 /* Note that strictly speaking __deprecated__ has been available before GCC 6. However, starting with GCC 6
  * it also works on enum values, which we are interested in. Since this is a developer-facing feature anyway
  * (as opposed to build engineer-facing), let's hence conditionalize this to gcc 6, given that the developers