Horton

Re: Compile error on the aarch64 platform: Missing asm/hwcap.h

Steven Niu <niushiji@gmail.com>

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From: Steven Niu <niushiji@gmail.com>
To: John Naylor <johncnaylorls@gmail.com>, 高增琦 <pgf00a@gmail.com>, "tmunro@postgresql.org" <tmunro@postgresql.org>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-11-17T03:56:22Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix pg_popcount_aarch64.c to build with ancient glibc releases.

  2. Fix pg_crc32c_armv8_choose.c to build with ancient glibc releases.

Hi, John,  Thomas,

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;
          |                                                                     ^~~~~~~~~~~

Then we tried to build source code of PG 18.1 and got the same failure result.

 I made some investigation to test the following code in src/port/pg_crc32c_armv8_choose.c

+#if defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
+#include <sys/auxv.h>
+#if defined(__linux__) && !defined(__aarch64__) && !defined(HWCAP2_CRC32)
+#include <asm/hwcap.h>
+#endif

// 1. Test defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
// Got #warning "CONDITION IS FALSE"
echo '#if defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
    #warning "CONDITION IS TRUE"
    #else
    #warning "CONDITION IS FALSE"
    #endif' | gcc -E -x c - -o -

// 2. Test defined(__linux__)
// Got true
echo '#if defined(__linux__)
    #warning "CONDITION IS TRUE"
    #else
    #warning "CONDITION IS FALSE"
    #endif' | gcc -E -x c - -o -

// 3. Test !defined(__aarch64__)
// Got false
echo '#if !defined(__aarch64__)
    #warning "CONDITION IS TRUE"
    #else
    #warning "CONDITION IS FALSE"
    #endif' | gcc -E -x c - -o -

// Test  !defined(HWCAP2_CRC32)
// Got true
echo '#if !defined(HWCAP2_CRC32)
    #warning "CONDITION IS TRUE"
    #else
    #warning "CONDITION IS FALSE"
    #endif' | gcc -E -x c - -o -


As a result, hwcap.h has no chance to be included in the building path.

So, my question is, why we exclude __aarch64__ in the second #if condition?

Thanks,
Steven

________________________________
From: John Naylor <johncnaylorls@gmail.com>
Sent: Friday, November 14, 2025 13:06
To: 高增琦 <pgf00a@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Compile error on the aarch64 platform: Missing asm/hwcap.h

On Fri, Nov 14, 2025 at 11:02 AM 高增琦 <pgf00a@gmail.com> wrote:
> Compile error on CentOS Linux release 7.6.1810 (AltArch) with the message “‘HWCAP_CRC32’ undeclared”.

We still have at least one CentOS 7 aarch64 machine that gets regular
testing (not sure of the reason, since it's been EOL for a year and a
half IIUC), and it builds fine:

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=arowana&dt=2025-11-04%2004%3A56%3A57

> After modifying the code to add `include <asm/hwcap.h>`, the compilation succeeded.

We already have the following, so I'm not sure what you mean (or even
what architecture you're running on):

#if defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
#include <sys/auxv.h>
#if defined(__linux__) && !defined(__aarch64__) && !defined(HWCAP2_CRC32)
#include <asm/hwcap.h>
#endif
#endif

--
John Naylor
Amazon Web Services