[Buildroot] [PATCH 1/1] package/alsa-lib: force -O2 on i386 with gcc >= 15.x

[Buildroot] [PATCH 1/1] package/alsa-lib: force -O2 on i386 with gcc >= 15.x

[Bernd Kuhls]

Fixes build error on i386:
pcm_dmix_i386.h: In function 'mix_areas_16':
pcm_dmix_i386.h:52:9: error: 'asm' operand has impossible constraints
 or there are not enough registers
   52 |         __asm__ __volatile__ (

Fixes:
https://autobuild.buildroot.net/results/fd9/fd9e6a6f9e2d37df3cfc1ed36707aef9a338f24d/

The oldest build error to be found dates back to Nov 2025:
https://autobuild.buildroot.net/results/3b6/3b606e0c6160563e410535d38a0e7bb09041f223/
so a backport to LTS branches should be considered.

The build error does not occur with gcc 14.4.0 and was reproduced with
gcc 16.1.0.

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
---
Gitlab pipelines passed:
https://gitlab.com/bkuhls/buildroot/-/commits/d022d480a4556f21d86172a593a92288018ed116

 package/alsa-lib/alsa-lib.mk | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/package/alsa-lib/alsa-lib.mk b/package/alsa-lib/alsa-lib.mk
index b6000b3cf3..40dbe0600d 100644
--- a/package/alsa-lib/alsa-lib.mk
+++ b/package/alsa-lib/alsa-lib.mk
@@ -18,6 +18,10 @@ ALSA_LIB_CONF_OPTS = \
 	--with-pcm-plugins="$(call qstrip,$(BR2_PACKAGE_ALSA_LIB_PCM_PLUGINS))" \
 	--with-ctl-plugins="$(call qstrip,$(BR2_PACKAGE_ALSA_LIB_CTL_PLUGINS))"
 
+ifeq ($(BR2_i386)$(BR2_TOOLCHAIN_GCC_AT_LEAST_15),yy)
+ALSA_LIB_CFLAGS += -O2
+endif
+
 ifeq ($(BR2_TOOLCHAIN_USES_GLIBC),)
 ALSA_LIB_CONF_OPTS += --without-versioned
 endif
-- 
2.47.3

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Re: [Buildroot] [PATCH 1/1] package/alsa-lib: force -O2 on i386 with gcc >= 15.x

[Thomas Petazzoni via buildroot]

On Sat, Jul 11, 2026 at 01:03:27PM +0200, Bernd Kuhls wrote:
> Fixes build error on i386:
> pcm_dmix_i386.h: In function 'mix_areas_16':
> pcm_dmix_i386.h:52:9: error: 'asm' operand has impossible constraints
>  or there are not enough registers
>    52 |         __asm__ __volatile__ (
> 
> Fixes:
> https://autobuild.buildroot.net/results/fd9/fd9e6a6f9e2d37df3cfc1ed36707aef9a338f24d/
> 
> The oldest build error to be found dates back to Nov 2025:
> https://autobuild.buildroot.net/results/3b6/3b606e0c6160563e410535d38a0e7bb09041f223/
> so a backport to LTS branches should be considered.
> 
> The build error does not occur with gcc 14.4.0 and was reproduced with
> gcc 16.1.0.

I have no doubt that passing -O2 works around the issue, but is this
the right fix? Especially since it didn't happen with gcc 14.x, it
does seem like a regression, no?

Could you make a bug report to GCC? Note that they want the
preprocessed source code to be able to easily reproduce.

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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