[oi-dev] Valgrind

[Paul Floyd]

On 15-02-25 18:58, stes at telenet.be wrote:
> 
> valgrind can run the OpenSmalltalk (a dialect or fork of Squeak) interpreter on OpenIndiana.
> 
> I reported a bug (not sure this is really a bug) for it  #17199.
> 
> This relates to https://illumos.org/man/7/epoll  because epoll can be enabled for OpenSmalltalk on OpenIndiana.
> 
> This is to my knowledge, different from Solaris, as the Illumos kernel supports Linux epoll.

If you want Valgrind bugs fixed than you're best off reporting it to 
https://bugs.kde.org. No promises - we have a big backlog and not enough 
contributors (something that you might be familiar with).

Looking at https://www.illumos.org/issues/17199

your error is

==3215== Syscall param write(buf) points to uninitialised byte(s)
==3215==    at 0x7FFEBE94A: __write (in /lib/amd64/libc.so.1)
==3215==    by 0x7FFE90550: epoll_ctl (in /lib/amd64/libc.so.1)

The syscall is 'write', not 'epoll'.

Without the source I can't be sure what is happening but this kind of 
error is quite common.

For syscalls that use either just scalar or array builtin types or fixed 
structs (like the 'stat' family) we can check the scalar/array/fields of 
the struct. Generic syscalls like 'read' and 'write' are a problem. All 
we get is a file descriptor, pointer and a length. We don't know what 
the pointer points to (we don't do any source analysis). That means that 
if the struct has any holes or padding amd hasn't been memset to zero we 
will see uninitialised bytes. We have no way to tell apart struct fields 
that from holes or padding.

That means that you have two choices.

1. Ensure that the struct gets memset to 0.
2. Use the Valgrind suppression mechanism to suppress the error.

A+
Paul