preprocessor/818: With -O2, preprocessor gives fatal error

[psmith@gnu.org]

>Number:         818
>Category:       preprocessor
>Synopsis:       With -O2, preprocessor gives fatal error
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Nov 15 14:46:00 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     Paul D. Smith
>Release:        GCC 2.95.2
>Organization:
>Environment:
Debian GNU/Linux 2.2+woody
GLIBC 2.1.95-1
>Description:
With the simple C code below, building without optimization:

  $ gcc -o ifdef.o -c ifdef.c
  $

With -O2:

  $ gcc -O2 -o ifdef.o -c ifdef.c
  ifdef.c:14: warning: preprocessing directive not recognized within macro arg
  ifdef.c:14: warning: preprocessing directive not recognized within macro arg
  ifdef.c:14: warning: preprocessing directive not recognized within macro arg
  ifdef.c: In function `foo_bar':
  ifdef.c:9: undefined or invalid # directive
  ifdef.c:11: undefined or invalid # directive
  ifdef.c:12: parse error before `2'
  ifdef.c:13: undefined or invalid # directive
  ifdef.c:14: parse error before `#'
  ifdef.c:14: `cray' undeclared (first use in this function)
  ifdef.c:14: (Each undeclared identifier is reported only once
  ifdef.c:14: for each function it appears in.)
  ifdef.c:14: parse error before `1'
  ifdef.c:14: parse error before `#'
  ifdef.c:14: parse error before `1'
  ifdef.c:14: parse error before `)'
  ifdef.c:14: `__s1_len' undeclared (first use in this function)
  ifdef.c:14: `__s2_len' undeclared (first use in this function)
  ifdef.c: At top level:
  ifdef.c:14: parse error before `)'
>How-To-Repeat:
Repeatable.
>Fix:
Workaround:
If I change the ifdefs to appear outside of the strncmp()
it works.  Apparently with optimization on the strncmp()
is expanded into inline code, and for some reason the
preprocessor doesn't resolve the conditionals appearing
within the function arguments _before_ that happens.
>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: application/octet-stream; name="ifdef.c"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="ifdef.c"

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