[xen staging] build: correct cppcheck-misra make rule

[patchbot@xxxxxxx]

commit c1db78cae105e5b166f41ecac7ccb8cbfd82693f
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Sep 26 11:07:48 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 26 11:07:48 2022 +0200

    build: correct cppcheck-misra make rule
    
    Having cppcheck-misra.json depend on cppcheck-misra.txt does not
    properly address the multiple targets problem. If cppcheck-misra.json
    is deleted from the build tree but cppcheck-misra.txt is still there,
    nothing will re-generate cppcheck-misra.json.
    
    With GNU make 4.3 or newer we could use the &: grouped target separator,
    but since we support older make as well we need to use some other
    mechanism. Convert the rule to a pattern one (with "cppcheck" kind of
    arbitrarily chosen as the stem), thus making known to make that both
    files are created by a single command invocation. Since, as a result,
    the JSON file is now "intermediate" from make's perspective, prevent it
    being deleted again by making it a prereq of .PRECIOUS.
    
    Fixes: 57caa5375321 ("xen: Add MISRA support to cppcheck make rule")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
 xen/Makefile | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/xen/Makefile b/xen/Makefile
index 106aff6a07..4e6e661261 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -746,11 +746,12 @@ cppcheck-version:
 # documentation file. Also generate a json file with the right arguments for
 # cppcheck in json format including the list of rules to ignore.
 #
-cppcheck-misra.txt: $(XEN_ROOT)/docs/misra/rules.rst 
$(srctree)/tools/convert_misra_doc.py
-       $(Q)$(PYTHON) $(srctree)/tools/convert_misra_doc.py -i $< -o $@ -j 
$(@:.txt=.json)
-
-# convert_misra_doc is generating both files.
-cppcheck-misra.json: cppcheck-misra.txt
+# convert_misra_doc.py, producing both targets at the same time, should be
+# executed only once. Utilize a pattern rule to achieve this effect, with the
+# stem kind of arbitrarily chosen to be "cppcheck".
+.PRECIOUS: %-misra.json
+%-misra.txt %-misra.json: $(XEN_ROOT)/docs/misra/rules.rst 
$(srctree)/tools/convert_misra_doc.py
+       $(Q)$(PYTHON) $(srctree)/tools/convert_misra_doc.py -i $< -o 
$*-misra.txt -j $*-misra.json
 
 # Put this in generated headers this way it is cleaned by include/Makefile
 $(objtree)/include/generated/compiler-def.h:
--
generated by git-patchbot for /home/xen/git/xen.git#staging