On Thursday, 1 January 2026 05:38:37 Brasilia Standard Time Simon Schröder via
Std-Proposals wrote:
> Are you suggesting that Linux distributions should ship two libraries and do
> some magic to select the right one? I think it is quite obvious why Linux
> distributions choose backwards compatibility.

*I* am suggesting that. And glibc has such magic:
$ ldd /bin/openssl
        linux-vdso.so.1 (0x00007f4b4c75c000)
        libssl.so.3 => /lib64/glibc-hwcaps/x86-64-v3/libssl.so.3.5.3
(0x00007f4b4c50f000)
        libcrypto.so.3 => /lib64/glibc-hwcaps/x86-64-v3/libcrypto.so.3.5.3
(0x00007f4b4be00000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f4b4ba00000)
        libjitterentropy.so.3 => /lib64/libjitterentropy.so.3
(0x00007f4b4c502000)
        libz.so.1 => /lib64/glibc-hwcaps/x86-64-v3/libz.so.1.3.1
(0x00007f4b4c4e8000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f4b4c75e000)

$ ldd /bin/kwrite | grep Qt6
        libQt6Widgets.so.6 => /lib64/libQt6Widgets.so.6 (0x00007f0a06200000)
        libQt6Gui.so.6 => /lib64/glibc-hwcaps/x86-64-v4/libQt6Gui.so.6.10.1
(0x00007f0a05600000)
        libQt6Core.so.6 => /lib64/glibc-hwcaps/x86-64-v4/libQt6Core.so.6.10.1
(0x00007f0a04e00000)
        libQt6Xml.so.6 => /lib64/libQt6Xml.so.6 (0x00007f0a06a1f000)
        libQt6DBus.so.6 => /lib64/libQt6DBus.so.6 (0x00007f0a04332000)
        libQt6Qml.so.6 => /lib64/libQt6Qml.so.6 (0x00007f0a02600000)
        libQt6TextToSpeech.so.6 => /lib64/libQt6TextToSpeech.so.6
(0x00007f0a03c72000)
        libQt6PrintSupport.so.6 => /lib64/libQt6PrintSupport.so.6
(0x00007f0a0253e000)
        libQt6Network.so.6 => /lib64/libQt6Network.so.6 (0x00007f0a02000000)
        libQt6Multimedia.so.6 => /lib64/libQt6Multimedia.so.6
(0x00007f0a00917000)
        libQt6WaylandClient.so.6 => /lib64/glibc-hwcaps/x86-64-v4/
libQt6WaylandClient.so.6.10.1 (0x00007f0a000c9000)

The glibc-hwcaps feature is not meant for binary-incompatible builds.

[I don't know why my distro isn't shipping v3 glibc. libc itself doesn't
benefit much from the upgrade, making constant use of IFUNC. But libm does, in
spite of IFUNC]

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Principal Engineer - Intel Data Center - Platform & Sys. Eng.