fails to build on arm 32-bit with GCC 9, because armv5 support has been dropped

[Sébastien Villemot]

Dear SBCL maintainers,

Support for ARMv5 has been removed in GCC 9 (see [1]).

As a consequence, it is no longer possible to build SBCL on GNU/Linux for ARM 32-bit, because src/runtime/Config.arm-linux adds the “-march=armv5”.

On Debian, the solution that I implemented consists in removing the ARM-specific flags from the GCC command line (so that the binary automatically aligns with the baseline for the ARM port). Ubuntu rather chose to use “-march=armv7-a” (see [2] for the discussion).

Best,

[1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b232e6b58e3766bc66fe08fdb7bcba1bdadda8a2
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=931795

[Sébastien Villemot (sebastien-villemot)]

Actually the “-marm” flag should not be dropped, it is needed. I have put it back on Debian.

[Douglas Katzman (dougk)]

Apropos of this, I was just asking on sbcl-devel whether we can drop support for 32-bit ARM older than ARMv6T2. Are you saying you care, or don't care? (I get that the gcc flags are also at issue)

https://groups.google.com/g/sbcl-devel/c/NkYGeHBVq8Y

[Sébastien Villemot (sebastien-villemot)]

Debian currently has two 32-bit ARM ports:
- "armel", whose baseline is ARMv5T
- "armhf", whose baseline is ARMv7 + VFPv3-D16

There are regularly discussions about whether to drop the oldest one (armel), but for the time being there is still a demand for it.

So I’d prefer that you keep the support for ARMv5T, but I could adapt if you were to drop it (I would basically have to ask for the removal of SBCL on our armel port).