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Re: [Libcdio-devel] RFC: libcdio to remove it's version of bool and requ

From: Thomas Schmitt
Subject: Re: [Libcdio-devel] RFC: libcdio to remove it's version of bool and require <stdbool.h> ?
Date: Sun, 15 Jul 2018 11:54:53 +0200


Rocky Bernstein wrote:
> stdbool.h is POSIX. See
> Thoughts?

... and earlier in a different thread:
> >  That will probably break the ABI, but I think I'm okay with that.

Indeed libcdio should do something about the riddling error messages which
appear if <stdbool.h> is included after <cdio/iso9660.h>. (In those
messages, "bool" is about the least prominent name.)

But breaking the ABI is of course not my personal favorite.

include/cdio/types.h already tries to communicate with "All the stdbool.h"
by defining macro __bool_true_false_are_defined .
Obviously my local stdbool.h does not really understand this. (gcc -H says
it is /usr/lib/gcc/x86_64-linux-gnu/4.9/include/stdbool.h .)

How about waving more flags there ?

The following code change compiles although in iso9660_private.h the header
<stdbool.h> is included after <cdio/iso9660.h> which in all branches would
cause compile time errors:


diff --git a/include/cdio/types.h b/include/cdio/types.h
index dc7e478..6c1a057 100644
--- a/include/cdio/types.h
+++ b/include/cdio/types.h
@@ -104,11 +104,15 @@ typedef uint8_t ubyte;
 #ifndef __cplusplus
+#ifndef _STDBOOL_H
-/* All the stdbool.h seem to define those */
+/* All the stdbool.h seem to define those (but not all seem to obey) */
 #ifndef __bool_true_false_are_defined
 #define __bool_true_false_are_defined 1
+/* Keep conflicting definitions out, now that own ones get created. */
+#define _STDBOOL_H
 #undef bool
 #undef true
 #undef false
@@ -122,6 +126,7 @@ typedef uint8_t ubyte;
 #define false 0
 #endif /* __bool_true_false_are_defined */
+#endif /* _STDBOOL_H */
 #endif /*C++*/
   /* some GCC optimizations -- gcc 2.5+ */
diff --git a/lib/iso9660/iso9660_private.h b/lib/iso9660/iso9660_private.h
index c5e1393..53b0264 100644
--- a/lib/iso9660/iso9660_private.h
+++ b/lib/iso9660/iso9660_private.h
@@ -32,6 +32,9 @@
 #include <cdio/types.h>

+/* <<< only for a test */
+#include <cdio/iso9660.h>
 # include <stdbool.h>

I see few potential for regression:
This change can hardly break existing applications, because they would run
into the compiler errors if they included stdbool.h after cdio/types.h.
If they included stdbool.h before cdio/types.h, then "#ifndef _STDBOOL_H"
should not be reached at all, and even if so it should do no harm, because
the first inclusion of stdbool.h should keep out further inclusions of

Have a nice day :)


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