c/10375: Function-local external decls of builtins don't get attributes

[Zack Weinberg]

>Number:         10375
>Category:       c
>Synopsis:       Function-local external decls of builtins don't get attributes
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 11 02:36:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     zack@codesourcery.com (Zack Weinberg)
>Release:        unknown-1.0
>Organization:
>Environment:

>Description:
GCC fails to optimize (e.g.)

extern void bar(void);
void foo() { extern void abort(void); abort(); bar(); }

when the function-local decl is the only one visible.  This
is because the "anticipated" declaration is at file scope and the function-local decl is considered to shadow it.

See attached test case for more extensive tests.
>How-To-Repeat:

>Fix:

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