Andrew Pinski [EMAIL PROTECTED] writes:
the one thing I have not heard through this
discussion is the real reason why the C standards comittee decided
signed overflow as being undefined.
I wasn't there, but my impression is that many of the optimization
issues we've talked about in this
The C Standard says that if a program has signed integer overflow its
behavior is undefined, and the undefined behavior can even precede the
overflow. To take an extreme example:
@c Inspired by Robert Dewar's example in
@c http://gcc.gnu.org/ml/gcc/2007-01/msg00038.html (2007-01-01).
@example
The C Standard says that if a program has signed integer overflow its
behavior is undefined, and the undefined behavior can even precede the
overflow. To take an extreme example:
@c Inspired by Robert Dewar's example in
@c http://gcc.gnu.org/ml/gcc/2007-01/msg00038.html (2007-01-01).
@example
Andrew Pinski [EMAIL PROTECTED] writes:
|
| [EMAIL PROTECTED] (Richard Kenner) writes:
|
|Many portable C programs assume that signed integer overflow wraps
around
|reliably using two's complement arithmetic.
|
|
| I was looking for an adjective that mean the programs work on
Paul Eggert [EMAIL PROTECTED] writes:
| Here are further patches I checked into the Autoconf documentation to
| reflect today's comments (some of which I received privately). Thanks
| to all of you. The trickiest bit was documenting one simple way to
| reliably detect overflow without
On Mon, 2007-01-01 at 22:27 -0500, Richard Kenner wrote:
I don't think -frisky is a good name for that option. A better name
would be -fstrict.
Or -pedantic? ;-)
-pedantic-codegen
:)
Laurent
Andrew Pinski writes:
This will always cause a trap on x86, even with -fwrapv so really
-fwrapv has a bug on x86. I will file this bug sometime later
tomorrow. Oh and fixing this bug will actually slow down users
of -fwrapv even more than what it is currently does because
you can no
On Sun, 2006-12-31 at 12:04 -0500, Robert Dewar wrote:
Duncan Sands wrote:
The C front-end performs this transformation too. I'm not claiming that the
back-end optimizers would actually do something sensible if the front-end
didn't transform this code (in fact they don't seem too), but
Laurent GUERBY wrote:
On Sun, 2006-12-31 at 12:04 -0500, Robert Dewar wrote:
Duncan Sands wrote:
The C front-end performs this transformation too. I'm not claiming that the
back-end optimizers would actually do something sensible if the front-end
didn't transform this code (in fact they
Harlan Stenn wrote:
When was AC_PROG_CC_C89 introduced?
2.59c, released 2006-04-12, according to the NEWS.
Speaking of which, how difficult would it be to list the oldest
version that will support each autoconf macro?
It's just a Small Matter of Programming to write a Perl script that 1)
Thanks, Steven!
H
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Bob Rossi wrote:
I know the target triplet is the cpu-vendor-os triplet where the
executable runs. Does changing the cpu from i386-pc-mingw32 to
i686-pc-mingw32 actually change executable that is created?
No (not unless your configure script does something unusual).
If not, does anyone know
Andrew Pinski [EMAIL PROTECTED] writes:
the one thing I have not heard through this
discussion is the real reason why the C standards comittee decided
signed overflow as being undefined.
I wasn't there, but my impression is that many of the optimization
issues we've talked about in this
Andrew Pinski [EMAIL PROTECTED] writes:
|
| [EMAIL PROTECTED] (Richard Kenner) writes:
|
|Many portable C programs assume that signed integer overflow wraps
around
|reliably using two's complement arithmetic.
|
|
| I was looking for an adjective that mean the programs work on
Paul Eggert [EMAIL PROTECTED] writes:
| Here are further patches I checked into the Autoconf documentation to
| reflect today's comments (some of which I received privately). Thanks
| to all of you. The trickiest bit was documenting one simple way to
| reliably detect overflow without
Andrew Pinski writes:
This will always cause a trap on x86, even with -fwrapv so really
-fwrapv has a bug on x86. I will file this bug sometime later
tomorrow. Oh and fixing this bug will actually slow down users
of -fwrapv even more than what it is currently does because
you can no
Andrew Pinski [EMAIL PROTECTED] writes:
the one thing I have not heard through this
discussion is the real reason why the C standards comittee decided
signed overflow as being undefined.
I wasn't there, but my impression is that many of the optimization
issues we've talked about in this
Stepan,
I guess you may have found something there. The fact that this option is
available again shows an acknowledgement that wchar.h has been an issue in the
past.
I have more e-mails to read in this thread, but is this the best solution or
should the configure script itself be made smarter
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
Hi Chris, and happy new year,
According to Chris McGuire on 1/3/2007 7:41 AM:
I guess the following hack forces configure to ignore wchar.h:
./configure ac_cv_header_wchar_h=no
I guess you may have found something there. The fact that this
A few comments:
Many portable C programs assume that signed integer overflow wraps around
reliably using two's complement arithmetic.
I'd replace portable C programs with widely-used C programs. The normal
use of portable means that it conforms to the standard.
Conversely, in at least one
Today I updated the Autoconf manual to contain the following
description of the current situation with signed integer overflow.
This section of the manual is intended to advise programmers what to
do about portable C programs in this area.
I think some discussion along these lines also
Many portable C programs assume that signed integer overflow wraps around
reliably using two's complement arithmetic.
I was looking for an adjective that mean the programs work on a wide
variety of platforms, and portable seems more appropriate than
widely-used.
Maybe just say what you
[EMAIL PROTECTED] (Richard Kenner) writes:
Many portable C programs assume that signed integer overflow wraps
around
reliably using two's complement arithmetic.
I was looking for an adjective that mean the programs work on a wide
variety of platforms, and portable seems
Here are further patches I checked into the Autoconf documentation to
reflect today's comments (some of which I received privately). Thanks
to all of you. The trickiest bit was documenting one simple way to
reliably detect overflow without converting to unsigned and back.
(At least, I
Andrew Pinski [EMAIL PROTECTED] writes:
|
| [EMAIL PROTECTED] (Richard Kenner) writes:
|
|Many portable C programs assume that signed integer overflow wraps
around
|reliably using two's complement arithmetic.
|
|
| I was looking for an adjective that mean the programs work on
Paul Eggert [EMAIL PROTECTED] writes:
| Here are further patches I checked into the Autoconf documentation to
| reflect today's comments (some of which I received privately). Thanks
| to all of you. The trickiest bit was documenting one simple way to
| reliably detect overflow without
Andrew Pinski writes:
This will always cause a trap on x86, even with -fwrapv so really
-fwrapv has a bug on x86. I will file this bug sometime later
tomorrow. Oh and fixing this bug will actually slow down users
of -fwrapv even more than what it is currently does because
you can no
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