[Buildroot] [PATCH v2] package/stunnel: fix build on ARM Thumb-1

[Buildroot] [PATCH v2] package/stunnel: fix build on ARM Thumb-1

[Yegor Yefremov via buildroot]

From: Yegor Yefremov <yegorslists@googlemail.com>

stunnel's configure unconditionally probes -fstack-clash-protection
using AX_APPEND_COMPILE_FLAGS. The probe compiles a trivial conftest.c,
which succeeds, so the flag ends up in CFLAGS. However, on ARM Thumb-1
gcc implements stack clash protection through -fstack-check=specific,
which it refuses for any real function body, so every source file fails
to build:

  stunnel.c:1003:1: sorry, unimplemented: '-fstack-check=specific' for Thumb-1

Force the corresponding autoconf cache variable to "no" on Thumb-1, in
the same way cmocka already works around this gcc limitation, and
consistently with the existing -fstack-protector-strong override.

Fixes:
https://autobuild.buildroot.org/results/3d691184ba83ba4d881632f2b2bb4da5aa50f491/

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Assisted-by: Claude:claude-opus-5
---
Changes v1 -> v2:
  - add fixes tag

 package/stunnel/stunnel.mk | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/package/stunnel/stunnel.mk b/package/stunnel/stunnel.mk
index a8eb652bff..473fc81900 100644
--- a/package/stunnel/stunnel.mk
+++ b/package/stunnel/stunnel.mk
@@ -17,6 +17,11 @@ STUNNEL_LICENSE_FILES = COPYING.md COPYRIGHT.md
 STUNNEL_CPE_ID_VENDOR = stunnel
 STUNNEL_SELINUX_MODULES = stunnel
 
+# gcc for ARM Thumb1 doesn't implement -fstack-clash-protection
+ifeq ($(BR2_ARM_INSTRUCTIONS_THUMB),y)
+STUNNEL_CONF_ENV += ax_cv_check_cflags___fstack_clash_protection=no
+endif
+
 ifeq ($(BR2_INIT_SYSTEMD),y)
 STUNNEL_DEPENDENCIES += systemd
 else
-- 
2.34.1

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Re: [Buildroot] [PATCH v2] package/stunnel: fix build on ARM Thumb-1

[Thomas Petazzoni via buildroot]

On Thu, Sep 17, 2026 at 02:52:42PM +0200, Yegor Yefremov via buildroot wrote:
> From: Yegor Yefremov <yegorslists@googlemail.com>
> 
> stunnel's configure unconditionally probes -fstack-clash-protection
> using AX_APPEND_COMPILE_FLAGS. The probe compiles a trivial conftest.c,
> which succeeds, so the flag ends up in CFLAGS. However, on ARM Thumb-1
> gcc implements stack clash protection through -fstack-check=specific,
> which it refuses for any real function body, so every source file fails
> to build:
> 
>   stunnel.c:1003:1: sorry, unimplemented: '-fstack-check=specific' for Thumb-1
> 
> Force the corresponding autoconf cache variable to "no" on Thumb-1, in
> the same way cmocka already works around this gcc limitation, and
> consistently with the existing -fstack-protector-strong override.
> 
> Fixes:
> https://autobuild.buildroot.org/results/3d691184ba83ba4d881632f2b2bb4da5aa50f491/
> 
> Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
> Assisted-by: Claude:claude-opus-5

Applied to master, thanks!

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [PATCH v2] package/stunnel: fix build on ARM Thumb-1

[Raphaël Mélotte via buildroot]

In reply of:
> stunnel's configure unconditionally probes -fstack-clash-protection
> using AX_APPEND_COMPILE_FLAGS. The probe compiles a trivial conftest.c,
> which succeeds, so the flag ends up in CFLAGS. However, on ARM Thumb-1
> gcc implements stack clash protection through -fstack-check=specific,
> which it refuses for any real function body, so every source file fails
> to build:
> 
>   stunnel.c:1003:1: sorry, unimplemented: '-fstack-check=specific' for Thumb-1
> 
> Force the corresponding autoconf cache variable to "no" on Thumb-1, in
> the same way cmocka already works around this gcc limitation, and
> consistently with the existing -fstack-protector-strong override.
> 
> Fixes:
> https://autobuild.buildroot.org/results/3d691184ba83ba4d881632f2b2bb4da5aa50f491/
> 
> Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
> Assisted-by: Claude:claude-opus-5

Applied to 2025.02.x, 2026.08.x. Thanks

> ---
> Changes v1 -> v2:
>   - add fixes tag
> 
>  package/stunnel/stunnel.mk | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/package/stunnel/stunnel.mk b/package/stunnel/stunnel.mk
> index a8eb652bff..473fc81900 100644
> --- a/package/stunnel/stunnel.mk
> +++ b/package/stunnel/stunnel.mk
> @@ -17,6 +17,11 @@ STUNNEL_LICENSE_FILES = COPYING.md COPYRIGHT.md
>  STUNNEL_CPE_ID_VENDOR = stunnel
>  STUNNEL_SELINUX_MODULES = stunnel
>  
> +# gcc for ARM Thumb1 doesn't implement -fstack-clash-protection
> +ifeq ($(BR2_ARM_INSTRUCTIONS_THUMB),y)
> +STUNNEL_CONF_ENV += ax_cv_check_cflags___fstack_clash_protection=no
> +endif
> +
>  ifeq ($(BR2_INIT_SYSTEMD),y)
>  STUNNEL_DEPENDENCIES += systemd
>  else
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