search for: wraparound

No idea why this happens: index-parse.y: In function 'yyparse': index-parse.c:1256:6: error: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Werror=strict-overflow] if (yyss + yystacksize - 1 <= yyssp) ^ It only happens on one machine, and not on any others, even though they have similar versions of gcc and bison installed. Rich. -- Richard Jones, Virtualization Group,...

A missing u64 cast causes a 32-Bit wraparound from 4096 MiB to 0 MiB and therefore total 0 MiB VRAM detected if card has 4096 Mib per FBP. Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com> --- drivers/gpu/drm/nouveau/nvkm/subdev/fb/ramgf100.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm...

On Mon, Dec 15, 2014 at 05:54:51PM +0000, Richard W.M. Jones wrote: > No idea why this happens: > > index-parse.y: In function 'yyparse': > index-parse.c:1256:6: error: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Werror=strict-overflow] > if (yyss + yystacksize - 1 <= yyssp) > ^ > > It only happens on one machine, and not on any others, even > though they have similar versions of gcc and bison installed. I should clarify .. O...

On Aug 22, 2008, at 9:34 AMPDT, Chris Lattner wrote: > > On Aug 22, 2008, at 9:30 AM, Vikram S. Adve wrote: > >> In the general case, I think you have to be conservative about this >> because programmers may deliberately want this kind of "wraparound" >> behavior, e.g., with periodic boundary conditions. But 99.9% of >> programs probably don't need that so it would be bad to penalize them >> for this corner case. In such a situation, I think you just have to >> support both choices, but choose the default as s...

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi All, We just experienced a very strange problem with Xen, and I''m wondering if anyone else has experienced it. We have a single host with three domUs - one is HVM, and the other two are paravirt. The HVM is a production environment, the paravirt are for demo/devel. I stopped the devel domU, and when I restarted it, the HVM stopped

When hash collision occurs and it's near ramht object boundary, we could read and possibly overwrite some memory after ramht object. Signed-off-by: Marcin Slusarz <marcin.slusarz at gmail.com> Cc: stable at vger.kernel.org --- drivers/gpu/drm/nouveau/core/core/ramht.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/nouveau/core/core/ramht.c

On Aug 22, 2008, at 9:30 AM, Vikram S. Adve wrote: > In the general case, I think you have to be conservative about this > because programmers may deliberately want this kind of "wraparound" > behavior, e.g., with periodic boundary conditions. But 99.9% of > programs probably don't need that so it would be bad to penalize them > for this corner case. In such a situation, I think you just have to > support both choices, but choose the default as sensibly as possi...

In the general case, I think you have to be conservative about this because programmers may deliberately want this kind of "wraparound" behavior, e.g., with periodic boundary conditions. But 99.9% of programs probably don't need that so it would be bad to penalize them for this corner case. In such a situation, I think you just have to support both choices, but choose the default as sensibly as possible. I di...

>However, there is one issue I have ignored - possibility of overflow in >the index expression. Suppose, we have such a loop: > for (i8 i = 0; i != 200; ++i) { > A[2 * i + 5] = ... > ... = A[2 * i + 3] > } >If both index expressions are evaluated in 8-bit arithmetic, >then the dependence equation should be solved in modular arithmetic: > 2 * i + 5 == 2 * (i +

...y unsigned, like the size of an object. IMO, we should revisit this if and when the deficiencies in the C++ Standard are addressed. The underlying problem is that the C family of languages mixes two orthogonal properties: value range and overflow behavior. There is no unsigned type with undefined wraparound. So the question becomes: What property is more important to reflect? Do we want catch unintended wraparound behavior using a sanitizer/make optimizations based on it? Do we need the additional range provided by an unsigned type? As Chandler says in one of his talks linked earlier: "If you nee...

...latitude. > Assuming this will never happen and doing optimizations on that basis > is valid, but so are other things. > An easy implementation, which often matches user expectations because > it is what most hardware does, > is to treat signed and unsigned overflow alike, with clean wraparound. In other words, our current implementation is correct. However, we are missing the opportunity to optimize some things. Trivial examples include some cases where you can't compute a simple loop count due to potential overflow. -Chris

...gt; > On Aug 22, 2008, at 9:34 AMPDT, Chris Lattner wrote: > >> >> On Aug 22, 2008, at 9:30 AM, Vikram S. Adve wrote: >> >>> In the general case, I think you have to be conservative about this >>> because programmers may deliberately want this kind of "wraparound" >>> behavior, e.g., with periodic boundary conditions. But 99.9% of >>> programs probably don't need that so it would be bad to penalize >>> them >>> for this corner case. In such a situation, I think you just have to >>> support both choic...

This fixes a regression introduced by "drm/nouveau: rework to new fence interface" (commit 29ba89b2371d466). The fence sequence should not be reset after creation, the old value is used instead. On destruction the final value is written, to prevent another source of accidental wraparound in case of a channel being destroyed after a hang, and unblocking any other channel that may wait on the about-to-be-deleted channel to signal. I'm nothing if not optimistic about any hope of recovery from that. ;-) Reported-by: Ted Percival <ted at tedp.id.au> Signed-off-by: Maarten La...

Hello everybody, I want to solve the following problem with Shorewall: I have a computer with one NIC (eth0) with an internal IP address (10.1.x.x), which is supposed to accept connections from various clients (10.2.x.x) and redirect them to another IP address (10.3.x.x) with a different destination port. For example: The software on the client computer is told to connect to the Shorewall

...achine code for a device with modular arithmetic instructions (not simulate such a device on a standard CPU)? In which case, won't the same assumptions that are embodied in the transformations for the case of unsigned 2's complement arithmetic (in your case with 256 bit unsigned words) with wraparound result in correct code? I suspect two issues will come up: 1. The optimizations in LLVM which can reason about "useful for optimization" features of wrapping unsigned values are probably not particularly strong at the moment, since most interest tends to be in the case of optimizations t...

I've been playing around with LLVM to write a backend for a rather "simple" (co-)processor. Assume that only three arithmetic instructions exist: ADD mod N, SUB mod N and MUL mod N. The modulus N is programmable and stored in a register. No ordinary arithmetic instructions are available. The word size is 256-bit. In other words, the following function, b + c mod N, corresponds to

...t; device with modular arithmetic instructions (not simulate such a device on > a standard CPU)? In which case, won't the same assumptions that are > embodied in the transformations for the case of unsigned 2's complement > arithmetic (in your case with 256 bit unsigned words) with wraparound > result in correct code? I suspect two issues will come up: > > 1. The optimizations in LLVM which can reason about "useful for > optimization" features of wrapping unsigned values are probably not > particularly strong at the moment, since most interest tends to be in th...

...d by "drm/nouveau: rework to new fence interface" >> (commit 29ba89b2371d466). >> >> The fence sequence should not be reset after creation, the old value is used instead. >> On destruction the final value is written, to prevent another source of accidental >> wraparound in case of a channel being destroyed after a hang, and unblocking any other >> channel that may wait on the about-to-be-deleted channel to signal. >> >> I'm nothing if not optimistic about any hope of recovery from that. ;-) >> >> Reported-by: Ted Percival <ted...

Hi, On Sun, 28 Feb 2016, Linus Torvalds wrote: > > So the kernel obviously is already using its own C dialect, that is > > pretty far from standard C. All these options also have a negative > > impact on the performance of the generated code. > > They really don't. They do. > Have you ever seen code that cared about signed integer overflow? > > Yeah,

Il 11/09/2013 00:27, James Sparenberg ha scritto: > I'm doing some experimenting in our Development lab and as a result > I'm kickstarting over and over Virtual guests. This is of course > causing the guest Id to increment by one with each test. I've > googled around and tried searching the list but have not found out > how (if at all) it would be possible to reset the