94 lines
4.1 KiB
Diff
94 lines
4.1 KiB
Diff
From cdaf655f73bb3be10d47ab6f00d71a8d0b1a81e3 Mon Sep 17 00:00:00 2001
|
||
From: Matthijs van Duin <matthijsvanduin@gmail.com>
|
||
Date: Wed, 21 Jul 2021 11:10:36 +0200
|
||
Subject: [PATCH] sd-bus: fix missing initializer in SD_BUS_VTABLE_END (#20253)
|
||
MIME-Version: 1.0
|
||
Content-Type: text/plain; charset=UTF-8
|
||
Content-Transfer-Encoding: 8bit
|
||
|
||
When two fields were added to the vtable.x.start struct, no initializers
|
||
for these were added to SD_BUS_VTABLE_END which also (ab)used that
|
||
struct (albeit sneakily by using non-designated initialization).
|
||
|
||
While C tolerates this, C++ prohibits these missing initializers, and
|
||
both g++ and clang++ will complain when using -Wextra.
|
||
|
||
This patch gives SD_BUS_VTABLE_END its own case in the union and
|
||
clarifies its initialization.
|
||
|
||
I tested the behaviour of g++ 10.2 and clang 11 in various cases. Both will warn
|
||
(-Wmissing-field-initializers, implied by -Wextra) if you provide initializers for some
|
||
but not all fields of a struct. Declaring x.end as empty struct or using an empty initializer
|
||
{} to initialize the union or one of its members is valid C++ but not C, although both gcc
|
||
and clang accept it without warning (even at -Wall -Wextra -std=c90/c++11) unless you
|
||
use -pedantic (which requires -std=c99/c++2a to support designated initializers).
|
||
|
||
Interestingly, .x = { .start = { 0, 0, NULL } } is the only initializer I found for the union
|
||
(among candidates for SD_BUS_VTABLE_END) where gcc doesn't zero-fill it entirely
|
||
when allocated on stack, it looked like it did in all other cases (I only examined this on
|
||
32-bit arm). clang always seems to initialize all bytes of the union.
|
||
|
||
[zjs: test case:
|
||
$ cat vtable-test.cc
|
||
#include "sd-bus.h"
|
||
|
||
const sd_bus_vtable vtable[] = {
|
||
SD_BUS_VTABLE_END
|
||
};
|
||
|
||
$ g++ -I src/systemd/ -Wall -Wmissing-field-initializers -c vtable-test.cc
|
||
vtable-test.cc:5:1: warning: missing initializer for member ‘sd_bus_vtable::<unnamed union>::<unnamed struct>::features’ [-Wmissing-field-initializers]
|
||
5 | };
|
||
| ^
|
||
vtable-test.cc:5:1: warning: missing initializer for member ‘sd_bus_vtable::<unnamed union>::<unnamed struct>::vtable_format_reference’ [-Wmissing-field-initializers]
|
||
|
||
$ clang++ -I src/systemd/ -Wmissing-field-initializers -c vtable-test.cc
|
||
vtable-test.cc:4:4: warning: missing field 'features' initializer [-Wmissing-field-initializers]
|
||
SD_BUS_VTABLE_END
|
||
^
|
||
src/systemd/sd-bus-vtable.h:188:28: note: expanded from macro 'SD_BUS_VTABLE_END'
|
||
.x = { { 0 } }, \
|
||
^
|
||
1 warning generated.
|
||
|
||
Both warnings are gone with the patch.]
|
||
|
||
(cherry picked from commit 654eaa403070d3c897454a5190603fda4071c3ff)
|
||
|
||
Conflict:NA
|
||
Reference:https://github.com/systemd/systemd/commit/cdaf655f73bb3be10d47ab6f00d71a8d0b1a81e3
|
||
---
|
||
src/systemd/sd-bus-vtable.h | 9 ++++++++-
|
||
1 file changed, 8 insertions(+), 1 deletion(-)
|
||
|
||
diff --git a/src/systemd/sd-bus-vtable.h b/src/systemd/sd-bus-vtable.h
|
||
index 75f8848360..35c942b16c 100644
|
||
--- a/src/systemd/sd-bus-vtable.h
|
||
+++ b/src/systemd/sd-bus-vtable.h
|
||
@@ -75,6 +75,9 @@ struct sd_bus_vtable {
|
||
uint64_t features;
|
||
const unsigned *vtable_format_reference;
|
||
} start;
|
||
+ struct {
|
||
+ size_t reserved;
|
||
+ } end;
|
||
struct {
|
||
const char *member;
|
||
const char *signature;
|
||
@@ -185,7 +188,11 @@ struct sd_bus_vtable {
|
||
{ \
|
||
.type = _SD_BUS_VTABLE_END, \
|
||
.flags = 0, \
|
||
- .x = { { 0 } }, \
|
||
+ .x = { \
|
||
+ .end = { \
|
||
+ .reserved = 0, \
|
||
+ }, \
|
||
+ }, \
|
||
}
|
||
|
||
#define _SD_ECHO(X) X
|
||
--
|
||
2.33.0
|
||
|