bug#30738: Invalid timezone (tzalloc failure) treated as out-of-memory

[Valery Ushakov]

Emacs 25 treats tzalloc(3) failure as out-of-memory condition.
E.g. when an invalid timezone is specified, it fails to start with:

$ TZ=FOOBAR emacs -nw
emacs: Memory exhausted--use M-x save-some-buffers then exit and restart Emacs


The code in tzlookup() also assumes that tzalloc(3) understands the
direct zone specification in the name/offset format.  I haven't
checked tzcode history, but this support is only a few years old
(around 2014, I'd estimate).  E.g. NetBSD-6 has older tzcode(3) that
doesn't support this feature.  This leads to a lot of "Memory
exhausted" errors when trying to use e.g. vc.el

  "encode-time" (0xffffa2d4)
  "apply" (0xffffa3fc)
  "vc-cvs-parse-entry" (0xffffa718)
  "vc-cvs-registered" (0xffffa9b0)
  "progn" (0xffffab44)
  "if" (0xffffac24)
  "vc-cvs-registered" (0xffffae7c)
  "apply" (0xffffae78)
  "vc-call-backend" (0xffffb188)
  0x1c65360 PVEC_COMPILED
  "mapc" (0xffffb5c8)
  "vc-registered" (0xffffb8d8)
  "vc-backend" (0xffffbbe8)
  "vc-refresh-state" (0xffffbfa0)
  "run-hooks" (0xffffc08c)
  "after-find-file" (0xffffc3b4)
  ...

-uwe