On NetBSD 7, I get a compilation error in hamt.h, at the token '_Atomic'.
On this platform, GCC is 4.8.x, __STDC_VERSION__ is 201112L, and
__STD_NO_ATOMICS__ is not defined. In these conditions, hamt.h defines
GL_HAMT_THREAD_SAFE to 1. It should define it to 0 instead.
2021-12-24 Bruno Haible <br...@clisp.org>
hamt: Fix compilation error on NetBSD 7.
* lib/hamt.h (GL_HAMT_THREAD_SAFE): Define to 0 if the compiler is a
GCC version < 4.9.
diff --git a/lib/hamt.h b/lib/hamt.h
index 5d553fc7d..440f34acc 100644
--- a/lib/hamt.h
+++ b/lib/hamt.h
@@ -56,13 +56,16 @@ _GL_INLINE_HEADER_BEGIN
/* The GL_HAMT_THREAD_SAFE flag is set if the implementation of hamts
is thread-safe as long as two threads do not simultaneously access
the same hamt. This is non-trivial as different hamts may share
- some structure. */
+ some structure.
+ We can define it only when the compiler supports _Atomic. For GCC,
+ it is supported starting with GCC 4.9. */
-#if (__STDC_VERSION__ < 201112 || defined __STD_NO_ATOMICS__) \
- && __GNUC__ + (__GNUC_MINOR >= 9) <= 4
-# define GL_HAMT_THREAD_SAFE 0
-#else
+#if (__GNUC__ + (__GNUC_MINOR >= 9) > 4) \
+ && __STDC_VERSION__ >= 201112L && !defined __STD_NO_ATOMICS__ \
+ && !defined __cplusplus
# define GL_HAMT_THREAD_SAFE 1
+#else
+# define GL_HAMT_THREAD_SAFE 0
#endif
#include <stdbool.h>
