Hi Paul, I did this: > (gl_tree_iterator_free): Mark as 'const'.
and now GCC gives me this warning: In file included from gl_avltree_oset.c:46: gl_anytree_oset.h:442:1: warning: 'const' attribute on function returning 'void' [-Wattributes] for static void _GL_ATTRIBUTE_CONST gl_tree_iterator_free (gl_oset_iterator_t *iterator _GL_ATTRIBUTE_MAYBE_UNUSED) { } The description you added in attribute.h: /* It is OK for a compiler to omit duplicate calls with the same arguments. This attribute is safe for a function that neither depends on nor affects observable state, and always returns exactly once - e.g., does not loop forever, and does not call longjmp. (This attribute is stricter than ATTRIBUTE_PURE.) */ /* Applies to: functions. */ #define ATTRIBUTE_CONST _GL_ATTRIBUTE_CONST makes perfect sense for a function that returns void. However, in view of the GCC documentation [1] the GCC warning basically means "the 'const' attribute here does not help me in doing common-subexpression elimination, since the return type is 'void'". To me, this is a pointless warning. Would you agree that a bug report to the GCC people makes sense? Bruno [1] https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Common-Function-Attributes.html