Date: Thu, 13 Jan 2022 20:09:40 -0800
From: Noah Misch <noah@leadboat.com>
To: Zhihong Yu <zyu@yugabyte.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: null iv parameter passed to combo_init()
Message-ID: <20220114040940.GA447185@rfd.leadboat.com>
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On Sun, Jan 09, 2022 at 06:45:09PM -0800, Zhihong Yu wrote:
> On Sun, Jan 9, 2022 at 1:27 PM Zhihong Yu <zyu@yugabyte.com> wrote:
> > After installing gcc-11, ./configure passed (with 0003-memcpy-null.patch).
> > In the output of `make check-world`, I don't see `runtime error`.

That's expected.  With -fsanitize-undefined-trap-on-error, the program will
generate SIGILL when UBSan detects undefined behavior.  To get "runtime error"
messages in the postmaster log, drop -fsanitize-undefined-trap-on-error.  Both
ways of running the tests have uses.  -fsanitize-undefined-trap-on-error is
better when you think the code is clean, because a zero "make check-world"
exit status confirms the code is clean.  Once you know the code is unclean in
some way, -fsanitize-undefined-trap-on-error is better for getting details.

> > Though there was a crash (maybe specific to my machine):
> >
> > Core was generated by
> > `/nfusr/dev-server/zyu/postgres/tmp_install/usr/local/pgsql/bin/postgres
> > --singl'.
> > Program terminated with signal SIGILL, Illegal instruction.
> > #0  0x000000000050642d in write_item.cold ()
> > Missing separate debuginfos, use: debuginfo-install
> > glibc-2.17-325.el7_9.x86_64 nss-pam-ldapd-0.8.13-25.el7.x86_64
> > sssd-client-1.16.5-10.el7_9.10.x86_64
> > (gdb) bt
> > #0  0x000000000050642d in write_item.cold ()
> > #1  0x0000000000ba9d1b in write_relcache_init_file ()
> > #2  0x0000000000bb58f7 in RelationCacheInitializePhase3 ()
> > #3  0x0000000000bd5cb5 in InitPostgres ()
> > #4  0x0000000000a0a9ea in PostgresMain ()

That is UBSan detecting undefined behavior.  A successful patch version will
fix write_item(), among many other places that are currently making
check-world fail.  I get the same when testing your v5 under "gcc (Debian
11.2.0-13) 11.2.0".  I used the same host as buildfarm member thorntail, and I
configured like this:

  ./configure -C --with-lz4 --prefix=$HOME/sw/nopath/pghead --enable-tap-tests --enable-debug --enable-depend --enable-cassert CC='ccache gcc-11 -fsanitize=undefined -fsanitize-undefined-trap-on-error' CFLAGS='-O2 -funwind-tables'

> Earlier I was using devtoolset-11 which had an `Illegal instruction` error.
> 
> I compiled / installed gcc-11 from source (which took whole afternoon).
> `make check-world` passed with patch v3.
> In tmp_install/log/install.log, I saw:
> 
> gcc -Wall -Wmissing-prototypes -Wpointer-arith
> -Wdeclaration-after-statement -Werror=vla -Wendif-labels
> -Wmissing-format-attribute -Wimplicit-fallthrough=3 -Wcast-function-type
> -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard
> -Wno-format-truncation -Wno-stringop-truncation -fsanitize=undefined
> -fsanitize-undefined-trap-on-error -I../../src/port -DFRONTEND
> -I../../src/include  -D_GNU_SOURCE   -c -o path.o path.c
> rm -f libpgport.a

Perhaps this self-compiled gcc-11 is defective, being unable to detect the
instances of undefined behavior that other builds detect.  If so, use the
"devtoolset-11" gcc instead.  You're also building without optimization; that
might be the problem.