Bug 4775 - egcs does not honor __extension__
Summary: egcs does not honor __extension__
Alias: None
Product: Red Hat Raw Hide
Classification: Retired
Component: egcs
Version: 1.0
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Nalin Dahyabhai
QA Contact:
Depends On:
TreeView+ depends on / blocked
Reported: 1999-08-30 05:00 UTC by Cristian Gafton
Modified: 2008-05-01 15:37 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 1999-09-22 14:17:44 UTC

Attachments (Terms of Use)

Description Cristian Gafton 1999-08-30 05:00:59 UTC
In /usr/include/bits/string2.h there are a number of
constructs like
   __u = __extension__ ((void *) __u + 2);

When this code is compile with -Wpointer-arith the compile
will complain about it:

/usr/include/bits/string2.h:419: warning: pointer of type
`void *' used in arithmetic
/usr/include/bits/string2.h:427: warning: pointer of type
`void *' used in arithmetic
/usr/include/bits/string2.h:432: warning: pointer of type
`void *' used in arithmetic
/usr/include/bits/string2.h:437: warning: pointer of type
`void *' used in arithmetic
/usr/include/bits/string2.h:439: warning: pointer of type
`void *' used in arithmetic
/usr/include/bits/string2.h:444: warning: pointer of type
`void *' used in arithmetic

Because these things are marked with __extension__ the
compiler should understand that that is the indended use and
quit whining. This is very annoying and we need it fixed
quite fast :-)

It seems to be a bug in the current compile - it seems that
gcc 2.95 does not ahve the problem, so maybe there is a
possibility of backporting a patch...

Comment 1 Jim Kingdon 1999-08-30 19:26:59 UTC
For Ulrich's reaction see

Are you sure this changed in GCC 2.95?  Looking at the source
to 2.95 I don't see anything which has __extension__ interact with
anything other than -pedantic (which is the way it is documented).

Off the top of my head it strikes me as better to patch glibc
(which recently changed on this point) rather than patching gcc
(which has not changed the behavior of __extension__ in a long
time), if we really do need something fast.  Patching gcc in a way
that the gcc maintainers won't end up liking would just make things

Comment 2 Cristian Gafton 1999-08-30 19:32:59 UTC
I do not get those warnings with gcc 2.95, so something changed and
made the compiler to correctly protect extensios against
-Wpointer-arith. It *is* a bug in the compiler.

Comment 3 Jim Kingdon 1999-08-30 20:11:59 UTC
I just tried this with the latest gcc from cvs and I got the same
warnings (test case enclosed in the email section).
If you want to point me to a gcc 2.95 binary (or wait for me to
download and build it), I can try that too but I really don't think
the version of gcc has much to do with it.  Were you using -O in
your tests (that is required since string.h tests __OPTIMIZE__)?

I mean, I'll send email to gcc-bugs and see if people have reactions
(and I can certainly write a patch if that is what we want).  But if
this is a matter of just backporting code which is already
there, I am missing something in a big way.

Comment 4 Jim Kingdon 1999-09-07 01:52:59 UTC
Patch at
and in egcs-1.1.2-23.

Comment 5 Jim Kingdon 1999-09-21 21:32:59 UTC
Still working on getting this into GCC:

Comment 6 Jim Kingdon 1999-09-22 14:17:59 UTC
Checked into GCC mainline (ChangeLog entry dated 22 Sep 1999).

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