Re: [Libguestfs] [nbdkit PATCH 0/2] stdin/out cleanups
On 4/7/20 2:55 AM, Richard W.M. Jones wrote:
On Sat, Apr 04, 2020 at 05:02:37PM -0500, Eric Blake wrote:
> This is what I've been playing with in response to my earlier question
> about what to do with 'nbdkit -s sh -'
> (https://www.redhat.com/archives/libguestfs/2020-April/msg00032.html)
>
> I'm still open to ideas on a better name, and/or whether adding
> <stdbool.h> to our public include files is a good idea (if not,
> returning int instead of bool is tolerable).
The answer is: no, we cannot use <stdbool.h>. This is because we
advertise that we support using the headers in plugins which are pure
C90 code.
We also test this -- see tests/Makefile.am test-ansi-c-plugin.la --
however it may be that the test doesn't work properly if it didn't
fail after your change.
Interesting - even with -std=c90 -pedantic, gcc is NOT flagging the use
of <stdbool.h> as a problem. Maybe we should open a glibc bug
requesting that it be taught to make <stdbool.h> error out if compiler
witness macros indicate it is being sucked in during pedantic c90
compilation. But it was easy enough to strengthen the test (now committed):
diff --git c/tests/test-ansi-c-plugin.c w/tests/test-ansi-c-plugin.c
index ff0b34d0..140d29ce 100644
--- c/tests/test-ansi-c-plugin.c
+++ w/tests/test-ansi-c-plugin.c
@@ -36,6 +36,16 @@
#include <nbdkit-plugin.h>
+/* C90 lacks <stdbool.h>, and even in C99 and later, we are permitted
+ * to use 'bool', 'true', and 'false' however we want if that
header
+ * is not included. Prove that nbdkit did not pollute the namespace.
+ */
+#if __bool_true_false_are_defined
+#error nbdkit polluted namespace with stdbool.h
+#else
+extern int true, false;
+#endif
+
/* This looks like a 100MB disk with one empty partition. */
static unsigned char bootsector[512] = {
0xfa, 0xb8, 0x00, 0x10, 0x8e, 0xd0, 0xbc, 0x00,
Also, the term 'ANSI C' is now ambiguous: newer ANSI has moved to
include C11 by reference, so you have to be clear when you mean ANSI
C89/ISO C90.
https://stackoverflow.com/questions/1608318/is-bool-a-native-c-type
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org