invert and rename PERL_MEM_LOG_STDERR to PERL_MEM_LOG_NOIMPL

Most users who want PERL_MEM_LOG want the default implementation,
give it to them.  Users providing their own implementation can
obtain current behavior by adding -DPERL_MEM_LOG_NOIMPL.
Frankly, the average user probably wants _ENV by default too.

1 files changed, 4 insertions, 2 deletions

diff --git a/handy.h b/handy.h
index 9e8f50a30b..d890f70994 100644
--- a/handy.h
+++ b/handy.h
@@ -761,7 +761,7 @@ PoisonWith(0xEF) for catching access to freed memory.
  * which more importantly get the immediate calling environment (file and
  * line number, and C function name if available) passed in.  This info can
  * then be used for logging the calls, for which one gets a sample
- * implementation if PERL_MEM_LOG_STDERR is defined.
+ * implementation unless -DPERL_MEM_LOG_NOIMPL is also defined.
  *
  * Known problems:
  * - all memory allocs do not get logged, only those
@@ -783,6 +783,8 @@ PoisonWith(0xEF) for catching access to freed memory.
  *   (keyed by the allocation address?), and maintain that
  *   through reallocs and frees, but how to do that without
  *   any News() happening...?
+ * - lots of -Ddefines to get useful/controllable output
+ * - lots of ENV reads when you get control -DPERL_MEM_LOG_ENV*
  */
 
 PERL_EXPORT_C Malloc_t Perl_mem_log_alloc(const UV n, const UV typesize, const char *type_name, Malloc_t newalloc, const char *filename, const int linenumber, const char *funcname);
@@ -792,7 +794,7 @@ PERL_EXPORT_C Malloc_t Perl_mem_log_realloc(const UV n, const UV typesize, const
 PERL_EXPORT_C Malloc_t Perl_mem_log_free(Malloc_t oldalloc, const char *filename, const int linenumber, const char *funcname);
 
 # ifdef PERL_CORE
-#  ifdef PERL_MEM_LOG_STDERR
+#  ifndef PERL_MEM_LOG_NOIMPL
 enum mem_log_type {
   MLT_ALLOC,
   MLT_REALLOC,