use cBOOL for bool casts

bool b = (bool)some_int

doesn't necessarily do what you think. In some builds, bool is defined as
char, and that cast's behaviour is thus undefined. So this line in mg.c:

    const bool was_temp = (bool)SvTEMP(sv);

was actually setting was_temp to false even when the SVs_TEMP flag was set.
Fix this by replacing all the (bool) casts with a new cBOOL() cast macro
that (hopefully) does the right thing.

1 files changed, 6 insertions, 0 deletions

diff --git a/handy.h b/handy.h
index 81bf1e270d..ebe523fbec 100644
--- a/handy.h
+++ b/handy.h
@@ -110,6 +110,12 @@ Null SV pointer. (No longer available when C<PERL_CORE> is defined.)
 # define HAS_BOOL 1
 #endif
 
+/* a simple (bool) cast may not do the right thing: if bool is defined
+ * as char for example, then the cast from int is implementation-defined
+ */
+
+#define cBOOL(cbool) ((bool)!!(cbool))
+
 /* Try to figure out __func__ or __FUNCTION__ equivalent, if any.
  * XXX Should really be a Configure probe, with HAS__FUNCTION__
  *     and FUNCTION__ as results.