c/7946: -std=gnu99 and casted empty srtuct initializers

c/7946: -std=gnu99 and casted empty srtuct initializers

[marcus]

>Number:         7946
>Category:       c
>Synopsis:       -std=gnu99 and casted empty srtuct initializers
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Tue Sep 17 06:26:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Marcus Brinkmann
>Release:        gcc (GCC) 3.2 (20020809) Debian prerelease
>Organization:
>Environment:
i386-gnu
>Description:
This bug only occurs with -std=gnu99.

Initializing an empty struct with an empty struct does not
work if the empty struct is explicitely casted to the struct
type.  GCC bails out with "initializer element not constant"
>How-To-Repeat:
Compile the following code with "gcc -std=gnu99":

typedef struct { } foo_t;

/* This one works.  */
foo_t bar = { };

/* This one fails with "initializer element is not constant.  */
foo_t baz = (foo_t) { };

int
main ()
{
  return 0;
}
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:

Re: c/7946: -std=gnu99 and casted empty srtuct initializers

[jsm28]

Synopsis: -std=gnu99 and casted empty srtuct initializers

State-Changed-From-To: open->closed
State-Changed-By: jsm28
State-Changed-When: Tue Sep 17 08:24:50 2002
State-Changed-Why:
    This is deliberate.  C99 compound literals are not
    constant expressions but unnamed variables intitialized
    in a given way.  The code you give is equivalent to
    
    foo_t compound_literal = { };
    foo_t baz = compound_literal;
    
    which of course fails.  As an allowance for existing
    code written for old GNU compound literals rather than
    C99 compound literals (the Linux kernel), this case
    is permitted in gnu89 mode but not gnu99 mode.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7946