2021-01-05 23:02:09

by Nathan Chancellor

Subject: [PATCH] MIPS: Use address-of operator on section symbols

When building xway_defconfig with clang:

arch/mips/lantiq/prom.c:82:23: error: array comparison always evaluates
to true [-Werror,-Wtautological-compare]
else if (__dtb_start != __dtb_end)
^
1 error generated.

These are not true arrays, they are linker defined symbols, which are
just addresses. Using the address of operator silences the warning
and does not change the resulting assembly with either clang/ld.lld
or gcc/ld (tested with diff + objdump -Dr). Do the same thing across
the entire MIPS subsystem to ensure there are no more warnings around
this type of comparison.

Link: https://github.com/ClangBuiltLinux/linux/issues/1232
Signed-off-by: Nathan Chancellor <[email protected]>
---
arch/mips/bmips/setup.c | 2 +-
arch/mips/lantiq/prom.c | 2 +-
arch/mips/pic32/pic32mzda/init.c | 2 +-
arch/mips/ralink/of.c | 2 +-
4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
index 19308df5f577..1b06b25aea87 100644
--- a/arch/mips/bmips/setup.c
+++ b/arch/mips/bmips/setup.c
@@ -167,7 +167,7 @@ void __init plat_mem_setup(void)
dtb = phys_to_virt(fw_arg2);
else if (fw_passed_dtb) /* UHI interface or appended dtb */
dtb = (void *)fw_passed_dtb;
- else if (__dtb_start != __dtb_end)
+ else if (&__dtb_start != &__dtb_end)
dtb = (void *)__dtb_start;
else
panic("no dtb found");
diff --git a/arch/mips/lantiq/prom.c b/arch/mips/lantiq/prom.c
index 51a218f04fe0..3f568f5aae2d 100644
--- a/arch/mips/lantiq/prom.c
+++ b/arch/mips/lantiq/prom.c
@@ -79,7 +79,7 @@ void __init plat_mem_setup(void)

if (fw_passed_dtb) /* UHI interface */
dtb = (void *)fw_passed_dtb;
- else if (__dtb_start != __dtb_end)
+ else if (&__dtb_start != &__dtb_end)
dtb = (void *)__dtb_start;
else
panic("no dtb found");
diff --git a/arch/mips/pic32/pic32mzda/init.c b/arch/mips/pic32/pic32mzda/init.c
index 50f376f058f4..f232c77ff526 100644
--- a/arch/mips/pic32/pic32mzda/init.c
+++ b/arch/mips/pic32/pic32mzda/init.c
@@ -28,7 +28,7 @@ static ulong get_fdtaddr(void)
if (fw_passed_dtb && !fw_arg2 && !fw_arg3)
return (ulong)fw_passed_dtb;

- if (__dtb_start < __dtb_end)
+ if (&__dtb_start < &__dtb_end)
ftaddr = (ulong)__dtb_start;

return ftaddr;
diff --git a/arch/mips/ralink/of.c b/arch/mips/ralink/of.c
index cbae9d23ab7f..2c9af61efc20 100644
--- a/arch/mips/ralink/of.c
+++ b/arch/mips/ralink/of.c
@@ -75,7 +75,7 @@ void __init plat_mem_setup(void)
*/
if (fw_passed_dtb)
dtb = (void *)fw_passed_dtb;
- else if (__dtb_start != __dtb_end)
+ else if (&__dtb_start != &__dtb_end)
dtb = (void *)__dtb_start;

__dt_setup_arch(dtb);

base-commit: 36bbbd0e234d817938bdc52121a0f5473b3e58f5
--
2.30.0

2021-01-07 16:31:56

by Thomas Bogendoerfer

Subject: Re: [PATCH] MIPS: Use address-of operator on section symbols

On Tue, Jan 05, 2021 at 01:18:27PM -0700, Nathan Chancellor wrote:
> When building xway_defconfig with clang:
>
> arch/mips/lantiq/prom.c:82:23: error: array comparison always evaluates
> to true [-Werror,-Wtautological-compare]
> else if (__dtb_start != __dtb_end)
> ^
> 1 error generated.
>
> These are not true arrays, they are linker defined symbols, which are
> just addresses. Using the address of operator silences the warning
> and does not change the resulting assembly with either clang/ld.lld
> or gcc/ld (tested with diff + objdump -Dr). Do the same thing across
> the entire MIPS subsystem to ensure there are no more warnings around
> this type of comparison.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1232
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
> arch/mips/bmips/setup.c | 2 +-
> arch/mips/lantiq/prom.c | 2 +-
> arch/mips/pic32/pic32mzda/init.c | 2 +-
> arch/mips/ralink/of.c | 2 +-
> 4 files changed, 4 insertions(+), 4 deletions(-)

applied to mips-next.

Thomas.

--
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