* [PATCHv3] exynos4210_gic: Suppress gcc9 format-truncation warnings
@ 2019-12-02 6:08 David Gibson
2019-12-02 16:08 ` Richard Henderson
0 siblings, 1 reply; 4+ messages in thread
From: David Gibson @ 2019-12-02 6:08 UTC (permalink / raw)
To: peter.maydell
Cc: i.mitsyanko, richard.henderson, qemu-devel, qemu-arm,
Philippe Mathieu-Daudé,
David Gibson
exynos4210_gic_realize() prints the number of cpus into some temporary
buffers, but it only allows 3 bytes space for it. That's plenty:
existing machines will only ever set this value to EXYNOS4210_NCPUS
(2). But the compiler can't always figure that out, so some[*] gcc9
versions emit -Wformat-truncation warnings.
We can fix that by hinting the constraint to the compiler with a
suitably placed assert().
[*] The bizarre thing here, is that I've long gotten these warnings
compiling in a 32-bit x86 container as host - Fedora 30 with
gcc-9.2.1-1.fc30.i686 - but it compiles just fine on my normal
x86_64 host - Fedora 30 with and gcc-9.2.1-1.fc30.x86_64.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Peter, up to you if you squeeze this in for qemu-4.2 or leave it until 5.0
Changes since v2:
* Moved the assert outside the for loop using a trick suggested by
Richard Henderson
Changes since v1:
* Used an assert to hint the compiler, instead of increasing the
buffer size.
---
hw/intc/exynos4210_gic.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/hw/intc/exynos4210_gic.c b/hw/intc/exynos4210_gic.c
index a1b699b6ba..ddd006aca6 100644
--- a/hw/intc/exynos4210_gic.c
+++ b/hw/intc/exynos4210_gic.c
@@ -293,6 +293,7 @@ static void exynos4210_gic_realize(DeviceState *dev, Error **errp)
char cpu_alias_name[sizeof(cpu_prefix) + 3];
char dist_alias_name[sizeof(cpu_prefix) + 3];
SysBusDevice *gicbusdev;
+ uint32_t n = s->num_cpu;
uint32_t i;
s->gic = qdev_create(NULL, "arm_gic");
@@ -313,7 +314,14 @@ static void exynos4210_gic_realize(DeviceState *dev, Error **errp)
memory_region_init(&s->dist_container, obj, "exynos4210-dist-container",
EXYNOS4210_EXT_GIC_DIST_REGION_SIZE);
- for (i = 0; i < s->num_cpu; i++) {
+ /*
+ * This clues in gcc that our on-stack buffers do, in fact have
+ * enough room for the cpu numbers. gcc 9.2.1 on 32-bit x86
+ * doesn't figure this out, otherwise and gives spurious warnings.
+ */
+ assert(n <= EXYNOS4210_NCPUS);
+ for (i = 0; i < n; i++) {
+
/* Map CPU interface per SMP Core */
sprintf(cpu_alias_name, "%s%x", cpu_prefix, i);
memory_region_init_alias(&s->cpu_alias[i], obj,
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCHv3] exynos4210_gic: Suppress gcc9 format-truncation warnings
2019-12-02 6:08 [PATCHv3] exynos4210_gic: Suppress gcc9 format-truncation warnings David Gibson
@ 2019-12-02 16:08 ` Richard Henderson
2019-12-02 17:44 ` Peter Maydell
0 siblings, 1 reply; 4+ messages in thread
From: Richard Henderson @ 2019-12-02 16:08 UTC (permalink / raw)
To: David Gibson, peter.maydell
Cc: i.mitsyanko, qemu-arm, Philippe Mathieu-Daudé, qemu-devel
On 12/1/19 6:08 AM, David Gibson wrote:
>
> - for (i = 0; i < s->num_cpu; i++) {
> + /*
> + * This clues in gcc that our on-stack buffers do, in fact have
> + * enough room for the cpu numbers. gcc 9.2.1 on 32-bit x86
> + * doesn't figure this out, otherwise and gives spurious warnings.
> + */
> + assert(n <= EXYNOS4210_NCPUS);
> + for (i = 0; i < n; i++) {
> +
> /* Map CPU interface per SMP Core */
Watch out for the extra line added at the start of the block. Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCHv3] exynos4210_gic: Suppress gcc9 format-truncation warnings
2019-12-02 16:08 ` Richard Henderson
@ 2019-12-02 17:44 ` Peter Maydell
2019-12-03 0:21 ` David Gibson
0 siblings, 1 reply; 4+ messages in thread
From: Peter Maydell @ 2019-12-02 17:44 UTC (permalink / raw)
To: Richard Henderson
Cc: Igor Mitsyanko, qemu-arm, Philippe Mathieu-Daudé,
QEMU Developers, David Gibson
On Mon, 2 Dec 2019 at 16:08, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 12/1/19 6:08 AM, David Gibson wrote:
> >
> > - for (i = 0; i < s->num_cpu; i++) {
> > + /*
> > + * This clues in gcc that our on-stack buffers do, in fact have
> > + * enough room for the cpu numbers. gcc 9.2.1 on 32-bit x86
> > + * doesn't figure this out, otherwise and gives spurious warnings.
> > + */
> > + assert(n <= EXYNOS4210_NCPUS);
> > + for (i = 0; i < n; i++) {
> > +
> > /* Map CPU interface per SMP Core */
>
> Watch out for the extra line added at the start of the block. Otherwise,
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
I thought about putting this in rc4 but eventually decided
against it. Queued for 5.0 (with the stray extra blank line removed).
thanks
-- PMM
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCHv3] exynos4210_gic: Suppress gcc9 format-truncation warnings
2019-12-02 17:44 ` Peter Maydell
@ 2019-12-03 0:21 ` David Gibson
0 siblings, 0 replies; 4+ messages in thread
From: David Gibson @ 2019-12-03 0:21 UTC (permalink / raw)
To: Peter Maydell
Cc: Igor Mitsyanko, Philippe Mathieu-Daudé,
qemu-arm, Richard Henderson, QEMU Developers
[-- Attachment #1: Type: text/plain, Size: 1165 bytes --]
On Mon, Dec 02, 2019 at 05:44:11PM +0000, Peter Maydell wrote:
> On Mon, 2 Dec 2019 at 16:08, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> >
> > On 12/1/19 6:08 AM, David Gibson wrote:
> > >
> > > - for (i = 0; i < s->num_cpu; i++) {
> > > + /*
> > > + * This clues in gcc that our on-stack buffers do, in fact have
> > > + * enough room for the cpu numbers. gcc 9.2.1 on 32-bit x86
> > > + * doesn't figure this out, otherwise and gives spurious warnings.
> > > + */
> > > + assert(n <= EXYNOS4210_NCPUS);
> > > + for (i = 0; i < n; i++) {
> > > +
> > > /* Map CPU interface per SMP Core */
> >
> > Watch out for the extra line added at the start of the block. Otherwise,
> >
> > Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>
> I thought about putting this in rc4 but eventually decided
> against it. Queued for 5.0 (with the stray extra blank line
> removed).
Great!
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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2019-12-02 6:08 [PATCHv3] exynos4210_gic: Suppress gcc9 format-truncation warnings David Gibson
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2019-12-03 0:21 ` David Gibson
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