abort()/segfault when starting postgres in inaccessible CWD

Hi,

Starting postgres with a CWD that's not readable will trigger an Assert
and if those are disabled it presumably will segfault.

#0  0x00007ffff75621e5 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007ffff7565398 in __GI_abort () at abort.c:90
#2  0x000000000089031d in ExceptionalCondition (
    conditionName=0xa6e530 "!(((CurrentMemoryContext) != ((void *)0) && (((((const
Node*)((CurrentMemoryContext)))->type)== T_AllocSetContext))))", errorType=0xa6e2c9 "BadArgument", fileName=0xa6e240
"/home/andres/src/postgresql/src/backend/utils/mmgr/mcxt.c",lineNumber=649) 
    at /home/andres/src/postgresql/src/backend/utils/error/assert.c:54
#3  0x00000000008bc206 in palloc (size=1024) at /home/andres/src/postgresql/src/backend/utils/mmgr/mcxt.c:649
#4  0x00000000006597b2 in initStringInfo (str=0x7fffffffc410) at
/home/andres/src/postgresql/src/backend/lib/stringinfo.c:50
#5  0x0000000000896383 in expand_fmt_string (fmt=0xa8d3e8 "could not change directory to \"%s\": %s", edata=0xd587e0
<errordata>)
    at /home/andres/src/postgresql/src/backend/utils/error/elog.c:3167
#6  0x0000000000892c52 in elog_finish (elevel=15, fmt=0xa8d3e8 "could not change directory to \"%s\": %s")
    at /home/andres/src/postgresql/src/backend/utils/error/elog.c:1297
#7  0x00000000008d932a in resolve_symlinks (path=0x7fffffffdad0
"/home/andres/build/postgres/dev-assert/vpath/src/backend/postgres")
    at /home/andres/src/postgresql/src/port/exec.c:293
#8  0x00000000008d8e10 in find_my_exec (argv0=0xd60bb0
"/home/andres/build/postgres/dev-assert/vpath/src/backend/postgres", 
    retpath=0x7fffffffdad0 "/home/andres/build/postgres/dev-assert/vpath/src/backend/postgres")
    at /home/andres/src/postgresql/src/port/exec.c:144
#9  0x00000000008d96aa in set_pglocale_pgservice (argv0=0xd60bb0
"/home/andres/build/postgres/dev-assert/vpath/src/backend/postgres", 
    app=0xa05440 "postgres-9.4") at /home/andres/src/postgresql/src/port/exec.c:561
#10 0x0000000000668932 in main (argc=21, argv=0xd60af0) at /home/andres/src/postgresql/src/backend/main/main.c:98

So, the problem is that we're calling set_pglocale_pgservice() which
indirectly can call elog() long before we've initialized memory
contexts.

To reproduce do something like:

# become root
su
# change into root-only directory
cd /root
# switch user, without changing directory
su postgres
# execute postgres
/path/to/postgres -D frakbar

Greetings,

Andres Freund

--
 Andres Freund                       http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services