add a comment documenting STATIC_ASSERT_GLOBAL/STATIC_ASSERT_STMT

1 files changed, 12 insertions, 0 deletions

diff --git a/perl.h b/perl.h
index b6dbf61ea1..9976f86bdd 100644
--- a/perl.h
+++ b/perl.h
@@ -3510,6 +3510,18 @@ typedef pthread_key_t	perl_key;
 /* placeholder */
 #endif
 
+/* STATIC_ASSERT_GLOBAL/STATIC_ASSERT_STMT are like assert(), but for compile
+   time invariants. That is, their argument must be a constant expression that
+   can be verified by the compiler. This expression can contain anything that's
+   known to the compiler, e.g. #define constants, enums, or sizeof (...). If
+   the expression evaluates to 0, compilation fails.
+   Because they generate no runtime code (i.e.  their use is "free"), they're
+   always active, even under non-DEBUGGING builds.
+   STATIC_ASSERT_GLOBAL expands to a declaration and is suitable for use at
+   file scope (outside of any function).
+   STATIC_ASSERT_STMT expands to a statement and is suitable for use inside a
+   function.
+*/
 #if (defined(static_assert) || (defined(__cplusplus) && __cplusplus >= 201103L)) && (!defined(__IBMC__) || __IBMC__ >= 1210)
 /* static_assert is a macro defined in <assert.h> in C11 or a compiler
    builtin in C++11.