aarch64 builds fail on recent glibc

[Rex Dieter]

Seeing builds fail recently on more recent glibc releases (in fedora 27+). glibc-2.25 was known good, glibc-2.26+ seems to be problematic:

cc -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fno-pie -I. -DSBCL_PREFIX=\"'/usr'\" -c -o arm64-linux-os.o arm64-linux-os.c
arm64-linux-os.c: In function 'os_context_float_register_addr':
arm64-linux-os.c:101:57: error: 'mcontext_t {aka struct <anonymous>}' has no member named '__reserved'; did you mean '__glibc_reserved1'?
         &((struct fpsimd_context *)context->uc_mcontext.__reserved)->vregs[offset];
                                                         ^~~~~~~~~~
                                                         __glibc_reserved1
arm64-linux-os.c:102:1: warning: control reaches end of non-void function [-Wreturn-type]

[Rex Dieter (rdieter)]

Upon further tests, I've confirmed f27's glibc-2.26 is ok, it's only f28(rawhide)'s glibc-2.26.9000 development release that is affected.

[Stas Boukarev (stassats)]

What SBCL version?

[Stas Boukarev (stassats)]

Ok, doesn't matter, any version has this.

[Rex Dieter (rdieter)]

Sorry, I tested with 1.3.21 and 1.4.0 (but you're probably right)

[Stas Boukarev (stassats)]

In b5491dad9d2e582536e81f68057ee45388bb55d1