Hi,
Here's a similar ticket in another OSS.
https://github.com/bellard/quickjs/issues/225#issuecomment-1908279228
> QuickJS may pass NULL pointers to memcpy with zero size. The C spec tells
it is an undefined behavior but most C code do it, so the spec should be
fixed instead.
On Wed, Jan 24,
Hello!
On Wed, Jan 24, 2024 at 12:09:02AM +, Ben Kallus wrote:
> > As already pointed out previously, there are no known cases
> > when memcpy(p, NULL, 0) can result in miscompilation of nginx
> > code, ... If you think there are cases when the code can be
> > miscompiled in practice, and
Hi Maxim,
> As already pointed out previously, there are no known cases
> when memcpy(p, NULL, 0) can result in miscompilation of nginx
> code, ... If you think there are cases when the code can be
> miscompiled in practice, and not theoretically, please share.
There is no such thing as
Hello!
On Tue, Jan 09, 2024 at 04:18:06PM +, Ben Kallus wrote:
> > This demonstrates that your patch
> > is clearly insufficient. Further, Vladimir's patch is clearly
> > insufficient too, as shown for the another patch in the same
> > patch series.
>
> "Insufficient" only when compared to
> This demonstrates that your patch
> is clearly insufficient. Further, Vladimir's patch is clearly
> insufficient too, as shown for the another patch in the same
> patch series.
"Insufficient" only when compared to a hypothetical perfectly exhaustive
patch that requires "huge work," as you put
Hello!
On Wed, Jan 03, 2024 at 11:57:57PM +, Ben Kallus wrote:
> > Still, general style guidelines suggests that the code shouldn't
> > be written this way, and the only reason for j++ in the line in
> > question is that it mimics corresponding IPv4 code.
>
> > It's not "just happens".
>
>
> Still, general style guidelines suggests that the code shouldn't
> be written this way, and the only reason for j++ in the line in
> question is that it mimics corresponding IPv4 code.
> It's not "just happens".
The point I'm trying to make is that ensuring correctness with
function-like
Hello!
On Fri, Dec 29, 2023 at 04:50:36PM +, Ben Kallus wrote:
> > Still, -O0 is often used at least during development, and it might
> > be unreasonable to introduce extra function calls in basic
> > primitives.
>
> I don't think this is a major cause for concern. It is perfectly
>
> Still, -O0 is often used at least during development, and it might
> be unreasonable to introduce extra function calls in basic
> primitives.
I don't think this is a major cause for concern. It is perfectly
reasonable for ngx_memcpy be a wrapper function around memcpy; I think
most people would
Hello!
On Sat, Dec 16, 2023 at 04:26:37PM -0500, Ben Kallus wrote:
> > In general macro definitions in nginx are used everywhere for
> > efficiency reasons
>
> Clang inlines short functions with -O1, and GCC does so with -O2 or
> -O1 -finline-small-functions. Are there any platforms that Nginx
> In general macro definitions in nginx are used everywhere for
> efficiency reasons
Clang inlines short functions with -O1, and GCC does so with -O2 or
-O1 -finline-small-functions. Are there any platforms that Nginx needs
to support for which short function inlining isn't sufficient to solve
Hello!
On Fri, Dec 15, 2023 at 03:46:19PM +0100, Dipl. Ing. Sergey Brester via
nginx-devel wrote:
> Enclosed few thoughts to the subject:
>
> - since it is very rare situation that one needs only a memcpy without
> to know whether previous alloc may fail
>(e. g. some of pointers were
> - rewrite of `ngx_memcpy` define like here:
> ```
> + #define ngx_memcpy(dst, src, n) (void) ((n) == 0 ? (dst) : memcpy(dst,
> src, n))
> ```
> may introduce a regression or compat issues, e. g. fully functioning codes
> like that may become broken hereafter:
> ```
>
Enclosed few thoughts to the subject:
- since it is very rare situation that one needs only a memcpy without
to know whether previous alloc may fail
(e. g. some of pointers were NULL), me too thinks that the caller
should be responsible for the check.
So I would not extend ngx_memcpy or
Hello!
On Wed, Dec 13, 2023 at 11:09:28AM -0500, Ben Kallus wrote:
> Nginx executes numerous `memcpy`s from NULL during normal execution.
> `memcpy`ing to or from NULL is undefined behavior. Accordingly, some
> compilers (gcc -O2) make optimizations that assume `memcpy` arguments
> are not NULL.
Nginx executes numerous `memcpy`s from NULL during normal execution.
`memcpy`ing to or from NULL is undefined behavior. Accordingly, some
compilers (gcc -O2) make optimizations that assume `memcpy` arguments
are not NULL. Nginx with UBSan crashes during startup due to this
issue.
Consider the
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