On 2025-04-25 10:07, Jan Beulich wrote:
On 24.04.2025 23:45, Stefano Stabellini wrote:
On Thu, 24 Apr 2025, Jan Beulich wrote:
On 23.04.2025 19:54, victorm.l...@amd.com wrote:
From: Nicola Vetrini <nicola.vetr...@bugseng.com>
MISRA C Rules 21.1 ("#define and #undef shall not be used on a
reserved identifier or reserved macro name") and R21.2 ("A reserved
identifier or reserved macro name shall not be declared") violations
are not problematic for Xen, as it does not use the C or POSIX
libraries.
Xen uses -fno-builtin and -nostdinc to ensure this, but there are
still
__builtin_* functions from the compiler that are available so
a deviation is formulated for all identifiers not starting with
"__builtin_".
The missing text of a deviation for Rule 21.2 is added to
docs/misra/deviations.rst.
To avoid regressions, tag both rules as clean and add them to the
monitored set.
Signed-off-by: Nicola Vetrini <nicola.vetr...@bugseng.com>
Signed-off-by: Federico Serafini <federico.seraf...@bugseng.com>
Signed-off-by: Victor Lira <victorm.l...@amd.com>
While the rule is in the library section, ...
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -587,7 +587,31 @@ Deviations related to MISRA C:2012 Rules:
construct is deviated only in Translation Units that present
a violation
of the Rule due to uses of this macro.
- Tagged as `deliberate` for ECLAIR.
-
+
+ * - R21.1
+ - Rule 21.1 reports identifiers reserved for the C and POSIX
standard
+ libraries. Xen does not use such libraries and all
translation units
+ are compiled with option '-nostdinc', therefore there is no
reason to
+ avoid to use `#define` or `#undef` on such identifiers
except for those
+ beginning with `__builtin_` for which compilers may perform
(wrong)
+ optimizations.
+ - Tagged as `safe` for ECLAIR.
... I'd like to ask that it be explicitly clarified here that it's
solely
the library (and not e.g. the compiler itself) that are of concern
here.
The language can be clarified:
- Rule 21.1 reports identifiers reserved for the C and POSIX standard
libraries. Xen does not use such libraries and all translation units
are compiled with option '-nostdinc', therefore there is no reason
to
avoid to use `#define` or `#undef` on C and POSIX standard libraries
identifiers except for those beginning with `__builtin_` for which
compilers may perform (wrong) optimizations.
Which makes it more apparent that there is a gap: What about e.g.
__x86_64__?
That falls within what the rules cover, is not a C or POSIX standard
library
identifier, yet very clearly must not be fiddled with. Whereas the text
above deviates it.
Hi Jan,
that is true, even if unlikely: one approach could be to avoid deviating
predefined macros for all CUs as -nostdinc and -fno-builtins should take
care of the rest; this kind of deviation is not currently possible in
ECLAIR, but it might be in the future. I think this could be
accomplished also via some gcc trickery on each CU, though I'm not sure
how valued that is for Xen.
--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253
