diff --git a/tests/testsuite.h b/tests/testsuite.h
index 3a2a3626..46e99dfe 100644
--- a/tests/testsuite.h
+++ b/tests/testsuite.h
@@ -1,11 +1,10 @@
-/* We don't need perfect functions for these tests. */
-#undef malloc
-#undef memcmp
-#undef realloc
+/* Common definitions to include in the generated parsers.  See
+   AT_DATA_SOURCE_PROLOGUE. */
 
 /* In C++ pre C++11 it is standard practice to use 0 for the null
    pointer.  But GCC -std=c++98 with -Wzero-as-null-pointer-constant
-   warns about this.  Warning introduced in GCC 4.7. */
+   warns about this, although this is just no alternative!  Warning
+   introduced in GCC 4.7. */
 #if defined __cplusplus && __cplusplus < 201103L
 # if defined __GNUC__ && ! defined __clang__ && 407 <= __GNUC__ * 100 + __GNUC_MINOR__
 #  pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"