From: Jim Wilson <wilson@chestnut.cygnus.com>
To: Ian Lance Taylor <ian@cygnus.com>
Cc: rms@gnu.ai.mit.edu, drepper@cygnus.com, dm@sgi.com,
gcc2@cygnus.com, gas2@cygnus.com
Subject: Re: global vars and symbol visibility for mips32/elf
Date: Sat, 10 Aug 1996 23:26:00 -0000 [thread overview]
Message-ID: <199608110626.XAA06107@cygnus.com> (raw)
In-Reply-To: <9608110241.AA22482@tweedledumb.cygnus.com>
The case which causes trouble is when a program uses a common variable
(an uninitialized variable in C; most languages, including C++, have
no notion of common variables).
ANSI/ISO C also does not have common variables. A program with multiple
external definitions of a variable has undefined behaviour. However, C
compilers that make this work by treating uninitialized variables as
common are so prevalent that most people aren't aware of this. This
particular feature is mentioned in the `Common Extensions' appendix, in
the section `Multiple External Definitions'.
This also means that, technically, if you want to make sure that other
ANSI/ISO C compilers can compile your code, you must use -fno-common
in addition to -ansi and -pedantic.
Jim
next prev parent reply other threads:[~1996-08-10 23:26 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
1996-08-09 2:46 David S. Miller
1996-08-09 5:24 ` David S. Miller
1996-08-09 9:01 ` Ian Lance Taylor
1996-08-09 8:30 ` Ian Lance Taylor
1996-08-09 13:13 ` Ulrich Drepper
1996-08-09 15:30 ` Ian Lance Taylor
1996-08-10 17:37 ` Richard Stallman
1996-08-10 19:41 ` Ian Lance Taylor
1996-08-10 23:26 ` Jim Wilson [this message]
1996-08-11 1:44 ` Richard Stallman
1996-08-13 10:58 ` Ruediger Helsch
1996-08-13 13:36 ` Jim Wilson
1996-08-13 16:06 ` Ruediger Helsch
1996-08-13 19:04 ` Jim Wilson
1996-08-13 21:02 ` Richard Stallman
1996-08-14 3:06 ` Ruediger Helsch
1996-08-14 23:44 ` Richard Stallman
1996-08-14 0:18 ` Nick Ing-Simmons
1996-08-14 3:06 ` Ruediger Helsch
1996-08-15 11:24 ` H.J. Lu
1996-08-13 9:06 ` Ruediger Helsch
1996-08-13 10:58 ` Richard Stallman
1996-08-13 13:36 ` Ruediger Helsch
1996-08-13 13:36 ` Richard Stallman
1996-08-13 14:40 ` H.J. Lu
1996-08-13 16:06 ` Ulrich Drepper
1996-08-13 16:06 ` Joe Buck
1996-08-13 17:02 ` Rohan LENARD
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