[Xen-devel] [PATCH] tools/foreign: Avoid using alignment directives when not appropriate

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The foreign header generation blindly replaces 'uint64_t' with '__align8__
uint64_t', to get correct alignment when built as 32bit.  This is correct in
most circumstances, but Clang objects to two specific uses.

 * Inside a sizeof() expression
 * As part of a typecast

An example error looks like:

/local/xen.git/tools/libxc/../../tools/include/xen/foreign/x86_64.h:204:44:
error: 'aligned' attribute ignored when parsing type 
[-Werror,-Wignored-attributes]
    __align8__ uint64_t evtchn_mask[sizeof(__align8__ uint64_t) * 8];
                                           ^~~~~~~~~~
/local/xen.git/tools/libxc/../../tools/include/xen/foreign/x86_64.h:13:36:
note: expanded from macro '__align8__'
# define __align8__ __attribute__((aligned (8)))
                                   ^~~~~~~~~~~

This sedary is sufficient to fix all the bad examples without touching any of
the legitimate uses, and is more simple than teaching mkheader.py how to parse
C.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
---
 tools/include/xen-foreign/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/include/xen-foreign/Makefile 
b/tools/include/xen-foreign/Makefile
index 80a446a..b25bfa8 100644
--- a/tools/include/xen-foreign/Makefile
+++ b/tools/include/xen-foreign/Makefile
@@ -35,6 +35,8 @@ x86_32.h: mkheader.py structs.py 
$(ROOT)/arch-x86/xen-x86_32.h $(ROOT)/arch-x86/
 
 x86_64.h: mkheader.py structs.py $(ROOT)/arch-x86/xen-x86_64.h 
$(ROOT)/arch-x86/xen.h $(ROOT)/xen.h
        $(PYTHON) $< $* $@ $(filter %.h,$^)
+       #Avoid mixing an alignment directive with a uint64_t cast or sizeof 
expression
+       sed 's/(__align8__ uint64_t)/(uint64_t)/g' -i $@
 
 checker.c: mkchecker.py structs.py
        $(PYTHON) $< $@ $(architectures)
-- 
2.1.4


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