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From: "david at westcontrol dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/96284] New: Outdated C features should be made errors with
 newer standards
Date: Wed, 22 Jul 2020 13:16:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96284

            Bug ID: 96284
           Summary: Outdated C features should be made errors with newer
                    standards
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david at westcontrol dot com
  Target Milestone: ---

While C has tried to remain backwards compatible with each new standards
revision, some changes have been made so that particularly unsafe features =
from
old code are no longer supported.  gcc has (reasonably enough) tried to keep
support for old features, but when something has been deprecated for decade=
s,
perhaps it is time for it to be treated as an error by default and require =
an
explicit flag.  (This is in the same style as bug 85678 making "-fno-common"
the default.)

For example, implicit function declarations from K&R C were made obsolescen=
t in
C90, and removed from the language in C99.  But by default, they still only
cause a warning (-Wimplicit-function-declaration) in gcc, no matter what
standard is picked.

Could this be made an error by default (-Werror=3Dimplicit-function-declara=
tions)
?  Let those who want to compile old code with implicit function declaratio=
ns,
do so with an explicit flag.=