~ chicken-core (chicken-5) 44c2f63e04e1bca094f05f236e741c57071c844e

commit 44c2f63e04e1bca094f05f236e741c57071c844e
Author:     Jim Ursetto <zbigniewsz@gmail.com>
AuthorDate: Fri Jan 13 00:00:22 2012 -0600
Commit:     felix <felix@call-with-current-continuation.org>
CommitDate: Sat Feb 18 13:19:03 2012 +0100

    Use C_stack_pointer instead of C_alloc(0) when generating foreign callback stubs
    
    alloca(0) returns NULL in LLVM instead of returning the stack pointer,
    so generate a call to C_stack_pointer instead.  This is only necessary
    when adjusting the callback stack, as all other calls to C_alloc are
    omitted when their size is 0.

diff --git a/c-backend.scm b/c-backend.scm
index c5c81e0b..f41c59b6 100644
--- a/c-backend.scm
+++ b/c-backend.scm
@@ -1114,7 +1114,8 @@
 	 (when rname
 	   (gen #t "/* from " (cleanup rname) " */") )
 	 (generate-foreign-callback-header "" stub)
-	 (gen #\{ #t "C_word x,s=" sizestr ",*a=C_alloc(s);")
+	 (gen #\{ #t "C_word x,s=" sizestr ",*a="
+	      (if (string=? "0" sizestr) "C_stack_pointer;" "C_alloc(s);"))
 	 (gen #t "C_callback_adjust_stack(a,s);") ; make sure content is below stack_bottom as well
 	 (for-each
 	  (lambda (v t)