Mailing List Archive: [PATCH 1/7] xen/arm: Make make_cpus

When compiling at -Og:

domain_build.c: In function 'make_cpus_node':
domain_build.c:926:12: error: 'clock_valid' may be used uninitialized in this function [-Werror=maybe-uninitialized]
926 | if ( clock_valid )
| ^

The compiler hasn't spotted that clock_valid is always initialised after the
"if ( !compatible )" check. Initialise clock_valid to false.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
---
xen/arch/arm/domain_build.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index b1d7b9849f..b10f5c8f85 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -831,7 +831,7 @@ static int __init make_cpus_node(const struct domain *d, void *fdt)
/* Placeholder for cpu@ + a 32-bit hexadecimal number + \0 */
char buf[13];
u32 clock_frequency;
- bool clock_valid;
+ bool clock_valid = false;
uint64_t mpidr_aff;

dt_dprintk("Create cpus node\n");
--
2.11.0

Hi Andrew,

On 19/04/2021 15:01, Andrew Cooper wrote:
> When compiling at -Og:
>
> domain_build.c: In function 'make_cpus_node':
> domain_build.c:926:12: error: 'clock_valid' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 926 | if ( clock_valid )
> | ^
>
> The compiler hasn't spotted that clock_valid is always initialised after the
> "if ( !compatible )" check. Initialise clock_valid to false.

Can you confirm which version this is affecting? We bumped the minimum
version of GCC recently, so I want to make sure we don't add code to
silence older compilers.

> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Stefano Stabellini <sstabellini@kernel.org>
> CC: Julien Grall <julien@xen.org>
> CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
> ---
> xen/arch/arm/domain_build.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index b1d7b9849f..b10f5c8f85 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -831,7 +831,7 @@ static int __init make_cpus_node(const struct domain *d, void *fdt)
> /* Placeholder for cpu@ + a 32-bit hexadecimal number + \0 */
> char buf[13];
> u32 clock_frequency;
> - bool clock_valid;
> + bool clock_valid = false;

Would you mind to add something like:

/* Initialized silence at least GCC X.Y. */

With X.Y replaced with the version.

Cheers,

--
Julien Grall