[headerizer] Make the ASSERT_ARGS declaration look like the declaration

From: Mark Glines <mark@glines.org>

of a local variable.  This means we can put it at the very top of every
function, for maximum usefulness.
---

 include/parrot/exceptions.h |   10 ++++++++++
 tools/build/headerizer.pl   |    8 ++++----
 2 files changed, 14 insertions(+), 4 deletions(-)


diff --git a/include/parrot/exceptions.h b/include/parrot/exceptions.h
index eb6f494..f46b404 100644
--- a/include/parrot/exceptions.h
+++ b/include/parrot/exceptions.h
@@ -259,6 +259,16 @@ void Parrot_print_backtrace(void);
 #  define PARROT_ASSERT(x) (x) ? ((void)0) : Parrot_confess(#x, __FILE__, __LINE__)
 #endif
 
+/* having a function version of this lets us put ASSERT_ARGS() at the top
+ * of the list of local variables.  Thus, we can catch bad pointers before
+ * any of the local initialization logic is run.  And it always returns 0,
+ * so headerizer can define the ASSERT_ARGS_* macros like:
+ * int _ASSERT_ARGS = PARROT_ASSERT_ARG(a) || PARROT_ASSERT_ARG(b) || ...
+ */
+static inline int PARROT_ASSERT_ARG(const void *x) {
+    PARROT_ASSERT(x);
+    return 0;
+}
 #define ASSERT_ARGS(a) ASSERT_ARGS_ ## a
 
 
diff --git a/tools/build/headerizer.pl b/tools/build/headerizer.pl
index 8f7413b..a58ab8c 100644
--- a/tools/build/headerizer.pl
+++ b/tools/build/headerizer.pl
@@ -311,10 +311,10 @@ sub asserts_from_args {
                 # strip off everything before the final space or asterisk.
                 $var =~ s[.+[* ]([^* ]+)$][$1];
             }
-            push( @asserts, "assert($var);" );
+            push( @asserts, "PARROT_ASSERT_ARG($var)" );
         }
         if( $arg eq 'PARROT_INTERP' ) {
-            push( @asserts, "assert(interp);" );
+            push( @asserts, "PARROT_ASSERT_ARG(interp)" );
         }
     }
 
@@ -380,8 +380,8 @@ sub make_function_decls {
 
         my $assert = "#define ASSERT_ARGS_" . $func->{name};
         if(@asserts) {
-            $assert .= ' ';
-            $assert .= join(" \\\n" . ' ' x length($assert), @asserts);
+            $assert .= " __attribute__unused__ int _ASSERT_ARGS_CHECK = \\\n       ";
+            $assert .= join(" \\\n    || ", @asserts);
         }
         push(@decls, $assert);
     }