eal: fix internal ABI tag with clang

[ upstream commit 4ab63cd ]

Clang does not have an "error" attribute for functions, so for marking
internal functions we need to check for the error attribute, and provide
a fallback if it is not present. For clang, we can use "diagnose_if"
attribute, similarly checking for its presence before use.

Fixes: fba5af8 ("eal: add internal ABI tag definition")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

lib/librte_eal/include/rte_compat.h

@@ -19,12 +19,23 @@ __attribute__((section(".text.experimental")))
 
 #endif
 
-#ifndef ALLOW_INTERNAL_API
+#ifndef __has_attribute
+/* if no has_attribute assume no support for attribute too */
+#define __has_attribute(x) 0
+#endif
+
+#if !defined ALLOW_INTERNAL_API && __has_attribute(error) /* For GCC */
 
 #define __rte_internal \
 __attribute__((error("Symbol is not public ABI"), \
 section(".text.internal")))
 
+#elif !defined ALLOW_INTERNAL_API && __has_attribute(diagnose_if) /* For clang */
+
+#define __rte_internal \
+__attribute__((diagnose_if(1, "Symbol is not public ABI", "error"), \
+section(".text.internal")))
+
 #else
 
 #define __rte_internal \