Steven Niu <niushiji@gmail.com> writes:
> IvorySQL team found the same build issue on our building machine when we built IvorySQL code which is based on PG
18.0.
> pg_crc32c_armv8_choose.c:58:32:error:'HWCAP CRC32' undeclared(first use in this function)
> 58 | return (getauxval(AT_HWCAP) & HWCAP_CRC32) != θ;
> | ^~~~~~~~~~~
Bleah ... I confess to having misread the initial message as being a
complaint about HWCAP2_CRC32 not HWCAP_CRC32. -ENOCAFFEINE I guess.
So what we've got here is that somewhere along the line glibc decided
that sys/auxv.h should duplicate the HWCAPxxx macros from the kernel's
header. On recent (and even not so recent) aarch64 Fedora,
/usr/include/bits/hwcap.h has
/* The following must match the kernel's <asm/hwcap.h> and update the
list together with sysdeps/unix/sysv/linux/aarch64/dl-procinfo.c. */
#define HWCAP_FP (1 << 0)
...
but that is not the case if you go back as far as RHEL7.
A minimal fix might be to change
#if defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
#include <sys/auxv.h>
-#if defined(__linux__) && !defined(__aarch64__) && !defined(HWCAP2_CRC32)
+#if defined(__linux__)
#include <asm/hwcap.h>
#endif
#endif
but that risks compiler warnings if there are any macro discrepancies
at all between bits/hwcap.h and asm/hwcap.h. I'm inclined to think
it's better to do something like
+#if defined(__linux__) && (defined(__aarch64__) ? !defined(HWCAP_CRC32) : !defined(HWCAP2_CRC32))
or perhaps that's too unreadable and we should break it out into
multiple #if's.
regards, tom lane
