Never Say, Never Say Die! - the art of low-level Ruby and other Macabre Tales
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A lightning talk comparing low-level *nix programming in Ruby 1.9 using DL with Ruby 3.4 using Fiddle. Two examples are used. One is a simple POSIX semaphore which works as expected. The other covers various attempts to use the GNU libsigsegv library to recover from a segmentation fault. The talk was presented at LRUG in February 2025.
![[2001 edition]
My Dilemma
• Ruby is
a
notoriously high level
progr
a
mming l
a
ngu
a
ge
•
a
nd it's the one I most enjoy using
• but I
a
lso like to work on low-level things
• so I use C
• but do I re
a
lly need to?](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-2-320.jpg)
![[2025 edition]
My Dilemma
• Ruby is
a
notoriously high level
progr
a
mming l
a
ngu
a
ge
•
a
nd it's the one I most enjoy using
• but I
a
lso like to work on low-level things
• so I use Go
• but do I re
a
lly need to?](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-3-320.jpg)
![Semaphores with Kernel::syscall
[Ruby 1.9]
process 1
require ‘fcntl’
Open = 268
W
a
it = 271
Post = 273
Close = 269
s = sysc
a
ll Open, “/tmp/s”, Fcntl::O_CREAT, 1911
sysc
a
ll W
a
it, s
puts “locked
a
t #{Time.now}”
sleep 50
puts “posted
a
t #{Time.now}”
sysc
a
ll Post, s
sysc
a
ll Close, s
produces:
locked
a
t Thu M
a
y 28 01:03:23 +0100 2009
posted
a
t Thu M
a
y 28 01:04:13 +0100 2009
process 2
Open = 268
W
a
it = 271
TryW
a
it = 272
s = sysc
a
ll Open, “/tmp/s”
begin
t = Time.now
sysc
a
ll TryW
a
it, s
puts “locked
a
t #{t}”
rescue Exception => e
puts “busy
a
t #{t}”
sysc
a
ll W
a
it, s
puts “w
a
ited #{Time.now - t} seconds”
end
produces:
busy
a
t Thu M
a
y 28 01:03:36 +0100 2009
w
a
ited 47.056508 seconds](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-5-320.jpg)
![Semaphores with Kernel::syscall
[Ruby 3.4]
process 1
require ‘fcntl’
Open = 268
W
a
it = 271
Post = 273
Close = 269
s = sysc
a
ll Open, “/tmp/s”, Fcntl::O_CREAT, 1911
sysc
a
ll W
a
it, s
puts “locked
a
t #{Time.now}”
sleep 50
puts “posted
a
t #{Time.now}”
sysc
a
ll Post, s
sysc
a
ll Close, s
produces:
01
a
.rb:6:in '<m
a
in>': sysc
a
ll() function is unimplemented on this m
a
chine
(NotImplementedError)
from 01
a
.rb:6:in '<m
a
in>'
process 2
Open = 268
W
a
it = 271
TryW
a
it = 272
s = sysc
a
ll Open, “/tmp/s”
begin
t = Time.now
sysc
a
ll TryW
a
it, s
puts “locked
a
t #{t}”
rescue Exception => e
puts “busy
a
t #{t}”
sysc
a
ll W
a
it, s
puts “w
a
ited #{Time.now - t} seconds”
end
produces:
01b.rb:5:in '<m
a
in>': sysc
a
ll() function is unimplemented on this m
a
chine
(NotImplementedError)
from 01b.rb:5:in '<m
a
in>'](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-7-320.jpg)
![Semaphores with Kernel::syscall
[Ruby 3.4]
process 1
require ‘fcntl’
Open = 268
W
a
it = 271
Post = 273
Close = 269
s = sysc
a
ll Open, “/tmp/s”, Fcntl::O_CREAT, 1911
sysc
a
ll W
a
it, s
puts “locked
a
t #{Time.now}”
sleep 50
puts “posted
a
t #{Time.now}”
sysc
a
ll Post, s
sysc
a
ll Close, s
produces:
01
a
.rb:6:in '<m
a
in>': sysc
a
ll() function is unimplemented on this m
a
chine
(NotImplementedError)
from 01
a
.rb:6:in '<m
a
in>'
process 2
Open = 268
W
a
it = 271
TryW
a
it = 272
Post = 273
s = sysc
a
ll Open, “/tmp/s”
begin
t = Time.now
sysc
a
ll TryW
a
it, s
puts “locked
a
t #{t}”
rescue Exception => e
puts “busy
a
t #{t}”
sysc
a
ll W
a
it, s
puts “w
a
ited #{Time.now - t} seconds”
end
produces:
01b.rb:5:in '<m
a
in>': sysc
a
ll() function is unimplemented on this m
a
chine
(NotImplementedError)
from 01b.rb:5:in '<m
a
in>'
sysc
a
ll() function is unimplemented on this m
a
chine](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-8-320.jpg)
![dynamic library loading with DL
[Ruby 1.9]
process 1
require ‘dl’
require ‘fcntl’
LIBC = DL::dlopen ‘libc.dylib’
open = LIBC[‘sem_open’, ‘ISII’]
try_w
a
it = LIBC[‘sem_tryw
a
it’, ‘II’]
w
a
it = LIBC[‘sem_w
a
it’, ‘II’]
post = LIBC[‘sem_post’, ‘II’]
close = LIBC[‘sem_close’, ‘II’]
s = open.c
a
ll(“/tmp/s”, Fcntl::O_CREAT, 1911)[0]
w
a
it.c
a
ll s
puts “locked
a
t #{Time.now}”
sleep 50
puts “posted
a
t #{Time.now}”
post.c
a
ll s
close.c
a
ll s
=> locked
a
t Thu M
a
y 28 01:03:23 +0100 2009
=> posted
a
t Thu M
a
y 28 01:04:13 +0100 2009
process 2
require ‘dl’
require ‘fcntl’
LIBC = DL::dlopen ‘libc.dylib’
open = LIBC[‘sem_open’, ‘ISII’]
try_w
a
it = LIBC[‘sem_tryw
a
it’, ‘II’]
w
a
it = LIBC[‘sem_w
a
it’, ‘II’]
post = LIBC[‘sem_post’, ‘II’]
close = LIBC[‘sem_close’, ‘II’]
s = open.c
a
ll(“/tmp/s”)
t = Time.now
if try_w
a
it.c
a
ll(s)[0] == 0 then
puts “locked
a
t #{t}”
else
puts “busy
a
t #{t}”
w
a
it.c
a
ll s
puts “w
a
ited #{Time.now - t} seconds”
end
=> busy
a
t Thu M
a
y 28 01:03:36 +0100 2009
=> w
a
ited 47.056508 seconds](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-10-320.jpg)
![FFI foreign functions with Fiddle
[Ruby 3.4]
require ‘
f
iddle’
require ‘fcntl’
LIBC = Fiddle::dlopen 'libc++.dylib'
Open = Fiddle::Function.new(
LIBC['sem_open'],
[Fiddle::TYPE_CONST_STRING,
Fiddle::TYPE_INT,
Fiddle::TYPE_INT,
Fiddle::TYPE_UINT],
Fiddle::TYPE_VOIDP)
TryW
a
it = Fiddle::Function.new(
LIBC['sem_tryw
a
it'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
W
a
it = Fiddle::Function.new(
LIBC['sem_w
a
it'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
Post = Fiddle::Function.new(
LIBC['sem_post'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
Close = Fiddle::Function.new(
LIBC['sem_close'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
def report m, r = 0
puts "#{Time.now}: #{m}"
if r != 0
e = Fiddle::l
a
st_error
puts "terror = #{Errors[e]} [#{e}]"
end
end
process 1
report "cre
a
ting sem
a
phore"
s = Open.c
a
ll "/tmp/s", Fcntl::O_CREAT |
Fcntl::O_RDWR, 777, 0
puts s.inspect
report "sem
a
phore cre
a
ted"
sleep 15
r = Post.c
a
ll s
report "posted", r
sleep 5
t = Time.now
r = W
a
it.c
a
ll s
report "w
a
ited #{Time.now - t} seconds", r
r = Close.c
a
ll s
report "sem
a
phore destroyed"](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-11-320.jpg)
![FFI foreign functions with Fiddle
[Ruby 3.4]
require ‘
f
iddle’
require ‘fcntl’
LIBC = Fiddle::dlopen 'libc++.dylib'
Open = Fiddle::Function.new(
LIBC['sem_open'],
[Fiddle::TYPE_CONST_STRING,
Fiddle::TYPE_INT,
Fiddle::TYPE_INT,
Fiddle::TYPE_UINT],
Fiddle::TYPE_VOIDP)
TryW
a
it = Fiddle::Function.new(
LIBC['sem_tryw
a
it'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
W
a
it = Fiddle::Function.new(
LIBC['sem_w
a
it'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
Post = Fiddle::Function.new(
LIBC['sem_post'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
Close = Fiddle::Function.new(
LIBC['sem_close'],
[Fiddle::TYPE_VOIDP],
Fiddle::TYPE_INT)
def report m, r = 0
puts "#{Time.now}: #{m}"
if r != 0
e = Fiddle::l
a
st_error
puts "terror = #{Errors[e]} [#{e}]"
end
end
process 2
report "opening sem
a
phore"
s = Open.c
a
ll "/tmp/s"
puts s.inspect
r = TryW
a
it.c
a
ll s
report "locked"
if r then
report "busy", r
t = Time.now
r = W
a
it.c
a
ll s
report "w
a
ited #{Time.now - t}s", r
end
sleep 10
report "posted", Post.c
a
ll(s)](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-12-320.jpg)
![[Ruby 1.9]
require ‘dl’
memory_bu
ff
er = DL::m
a
lloc 20
=> #<DL::PtrD
a
t
a
:0x2d0870 ptr=0x820600 size=20 free=0x1b0257>
memory_bu
ff
er[0] = “hello world!”
=> “hello world!000000000000000000000000"
memory_bu
ff
er.free
=> #<DL::Symbol:0x40b760 func=0x1b0257 'void (free)(void *);'>
memory_bu
ff
er.nil
=> nil
malloc = fun](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-13-320.jpg)
![[Ruby 1.9]
string = “hello ruby”
memory_bu
ff
er = string.to_ptr
=> #<DL::PtrD
a
t
a
:0x41be
a
0 ptr=0x41be60 size=10 free=0x1b0257>
memory_bu
ff
er[0] = “goodbye world”
memory_bu
ff
er += 1
=> #<DL::PtrD
a
t
a
:0x422000 ptr=0x41be61 size=9 free=0x0>
puts memory_bu
ff
er, memory_bu
ff
er.to_str, string
=> “oodbye world”
=> “oodbye wo”
=> “hello ruby”
memory_bu
ff
er -= 1
=> (irb):51: [BUG] Segment
a
tion f
a
ult
...and frustration](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-14-320.jpg)
![[Ruby 1.9]
Sign
a
l.tr
a
p(:SEGV) { $stderr.puts "segf
a
ult triggered" }
Process.kill :SEGV, 0
$stderr.puts "but I c
a
rry on
a
s usu
a
l"
require 'dl'
memory = DL::m
a
lloc 1
4096.times { |i| memory[0] = 42.chr * i }
$stderr.puts "even genuine segf
a
ults don't ph
a
se me"
should produce:
segf
a
ult triggered
but I c
a
rry on
a
s usu
a
l
but we can
fi
x that?](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-15-320.jpg)
![[Ruby 1.9]
Sign
a
l.tr
a
p(:SEGV) { $stderr.puts "segf
a
ult triggered" }
Process.kill :SEGV, 0
but we can
fi
x that?
SIGSEGV in not
a
tr
a
pp
a
ble sign
a
l](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-16-320.jpg)
![[Ruby 3.4]
Sign
a
l.tr
a
p(:SEGV) { $stderr.puts "segf
a
ult triggered" }
Process.kill :SEGV, 0
but we can
fi
x that?
a
nd it prob
a
bly never will be](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-17-320.jpg)
![[Ruby 1.9]
require 'dl'
require ‘nevers
a
ydie’
memory = DL::m
a
lloc 1
4096.times do |i|
begin
puts "#{i} : #{(memory[1] = 42.chr * i).length}"
rescue NeverS
a
yDie => e
$stderr.puts "even genuine segf
a
ults don't ph
a
se me"
bre
a
k
end
end
produces:
even genuine segf
a
ults don't ph
a
se me
maybe with some tenderlove?
wr
a
ps GNU libsigsegv
a
ctu
a
lly works](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-18-320.jpg)
![[Ruby 3.4] https://github.com/tenderlove/neversaydie
gem inst
a
ll nevers
a
ydie
maybe with some tenderlove?
nevers
a
ydie doesn't build
uses CONFIG r
a
ther th
a
n RbCon
f
ig](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-19-320.jpg)
![[Ruby 1.9]
require 'dl'
SIGSEGV = DL::dlopen('libsigsegv.dylib')
inst
a
ll_h
a
ndler = SIGSEGV['sigsegv_inst
a
ll_h
a
ndler', 'IP']
deinst
a
ll_h
a
ndler = SIGSEGV['sigsegv_deinst
a
ll_h
a
ndler', '0']
le
a
ve_h
a
ndler = SIGSEGV['sigsegv_le
a
ve_h
a
ndler', 'IPPPP']
continu
a
tion = DL.c
a
llb
a
ck('IPPP') do |
a
ddress, b, c|
r
a
ise RuntimeError, "segf
a
ult
a
t #{
a
ddress}"
end
h
a
ndler = DL.c
a
llb
a
ck('IPI') do |f
a
ult_
a
ddress, serious|
le
a
ve_h
a
ndler.c
a
ll continu
a
tion, f
a
ult_
a
ddress, nil, nil
end
inst
a
ll_h
a
ndler.c
a
ll h
a
ndler
could this instead be done with DL?](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-20-320.jpg)
![[Ruby 1.9]
require 'dl'
SIGSEGV = DL::dlopen('libsigsegv.dylib')
inst
a
ll_h
a
ndler = SIGSEGV['sigsegv_inst
a
ll_h
a
ndler', 'IP']
deinst
a
ll_h
a
ndler = SIGSEGV['sigsegv_deinst
a
ll_h
a
ndler', '0']
le
a
ve_h
a
ndler = SIGSEGV['sigsegv_le
a
ve_h
a
ndler', 'IPPPP']
continu
a
tion = DL.c
a
llb
a
ck('IPPP') do |
a
ddress, b, c|
r
a
ise RuntimeError, "segf
a
ult
a
t #{
a
ddress}"
end
h
a
ndler = DL.c
a
llb
a
ck('IPI') do |f
a
ult_
a
ddress, serious|
le
a
ve_h
a
ndler.c
a
ll continu
a
tion, f
a
ult_
a
ddress, nil, nil
end
inst
a
ll_h
a
ndler.c
a
ll h
a
ndler
could this instead be done with DL?
NO!!!!
the registered h
a
ndler is never c
a
lled](https://image.slidesharecdn.com/2025neversayneversaydie-250214214039-2fb11228/85/Never-Say-Never-Say-Die-the-art-of-low-level-Ruby-and-other-Macabre-Tales-21-320.jpg)
Never Say, Never Say Die! - the art of low-level Ruby and other Macabre Tales
- 1. slideshare://feyeleanor the art of low-level ruby and other macabre tales Eleanor McHugh Never Say, "Never Say Die!"
- 2. [2001 edition] My Dilemma • Ruby is a notoriously high level progr a mming l a ngu a ge • a nd it's the one I most enjoy using • but I a lso like to work on low-level things • so I use C • but do I re a lly need to?
- 3. [2025 edition] My Dilemma • Ruby is a notoriously high level progr a mming l a ngu a ge • a nd it's the one I most enjoy using • but I a lso like to work on low-level things • so I use Go • but do I re a lly need to?
- 4. Ruby 1.9 could get pretty freaky
- 5. Semaphores with Kernel::syscall [Ruby 1.9] process 1 require ‘fcntl’ Open = 268 W a it = 271 Post = 273 Close = 269 s = sysc a ll Open, “/tmp/s”, Fcntl::O_CREAT, 1911 sysc a ll W a it, s puts “locked a t #{Time.now}” sleep 50 puts “posted a t #{Time.now}” sysc a ll Post, s sysc a ll Close, s produces: locked a t Thu M a y 28 01:03:23 +0100 2009 posted a t Thu M a y 28 01:04:13 +0100 2009 process 2 Open = 268 W a it = 271 TryW a it = 272 s = sysc a ll Open, “/tmp/s” begin t = Time.now sysc a ll TryW a it, s puts “locked a t #{t}” rescue Exception => e puts “busy a t #{t}” sysc a ll W a it, s puts “w a ited #{Time.now - t} seconds” end produces: busy a t Thu M a y 28 01:03:36 +0100 2009 w a ited 47.056508 seconds
- 6. so what about Ruby 3.4?
- 7. Semaphores with Kernel::syscall [Ruby 3.4] process 1 require ‘fcntl’ Open = 268 W a it = 271 Post = 273 Close = 269 s = sysc a ll Open, “/tmp/s”, Fcntl::O_CREAT, 1911 sysc a ll W a it, s puts “locked a t #{Time.now}” sleep 50 puts “posted a t #{Time.now}” sysc a ll Post, s sysc a ll Close, s produces: 01 a .rb:6:in '<m a in>': sysc a ll() function is unimplemented on this m a chine (NotImplementedError) from 01 a .rb:6:in '<m a in>' process 2 Open = 268 W a it = 271 TryW a it = 272 s = sysc a ll Open, “/tmp/s” begin t = Time.now sysc a ll TryW a it, s puts “locked a t #{t}” rescue Exception => e puts “busy a t #{t}” sysc a ll W a it, s puts “w a ited #{Time.now - t} seconds” end produces: 01b.rb:5:in '<m a in>': sysc a ll() function is unimplemented on this m a chine (NotImplementedError) from 01b.rb:5:in '<m a in>'
- 8. Semaphores with Kernel::syscall [Ruby 3.4] process 1 require ‘fcntl’ Open = 268 W a it = 271 Post = 273 Close = 269 s = sysc a ll Open, “/tmp/s”, Fcntl::O_CREAT, 1911 sysc a ll W a it, s puts “locked a t #{Time.now}” sleep 50 puts “posted a t #{Time.now}” sysc a ll Post, s sysc a ll Close, s produces: 01 a .rb:6:in '<m a in>': sysc a ll() function is unimplemented on this m a chine (NotImplementedError) from 01 a .rb:6:in '<m a in>' process 2 Open = 268 W a it = 271 TryW a it = 272 Post = 273 s = sysc a ll Open, “/tmp/s” begin t = Time.now sysc a ll TryW a it, s puts “locked a t #{t}” rescue Exception => e puts “busy a t #{t}” sysc a ll W a it, s puts “w a ited #{Time.now - t} seconds” end produces: 01b.rb:5:in '<m a in>': sysc a ll() function is unimplemented on this m a chine (NotImplementedError) from 01b.rb:5:in '<m a in>' sysc a ll() function is unimplemented on this m a chine
- 9. Not implemented on all platforms... linux 32-bit macOS 15.3 64-bit Windows 11 64-bit
- 10. dynamic library loading with DL [Ruby 1.9] process 1 require ‘dl’ require ‘fcntl’ LIBC = DL::dlopen ‘libc.dylib’ open = LIBC[‘sem_open’, ‘ISII’] try_w a it = LIBC[‘sem_tryw a it’, ‘II’] w a it = LIBC[‘sem_w a it’, ‘II’] post = LIBC[‘sem_post’, ‘II’] close = LIBC[‘sem_close’, ‘II’] s = open.c a ll(“/tmp/s”, Fcntl::O_CREAT, 1911)[0] w a it.c a ll s puts “locked a t #{Time.now}” sleep 50 puts “posted a t #{Time.now}” post.c a ll s close.c a ll s => locked a t Thu M a y 28 01:03:23 +0100 2009 => posted a t Thu M a y 28 01:04:13 +0100 2009 process 2 require ‘dl’ require ‘fcntl’ LIBC = DL::dlopen ‘libc.dylib’ open = LIBC[‘sem_open’, ‘ISII’] try_w a it = LIBC[‘sem_tryw a it’, ‘II’] w a it = LIBC[‘sem_w a it’, ‘II’] post = LIBC[‘sem_post’, ‘II’] close = LIBC[‘sem_close’, ‘II’] s = open.c a ll(“/tmp/s”) t = Time.now if try_w a it.c a ll(s)[0] == 0 then puts “locked a t #{t}” else puts “busy a t #{t}” w a it.c a ll s puts “w a ited #{Time.now - t} seconds” end => busy a t Thu M a y 28 01:03:36 +0100 2009 => w a ited 47.056508 seconds
- 11. FFI foreign functions with Fiddle [Ruby 3.4] require ‘ f iddle’ require ‘fcntl’ LIBC = Fiddle::dlopen 'libc++.dylib' Open = Fiddle::Function.new( LIBC['sem_open'], [Fiddle::TYPE_CONST_STRING, Fiddle::TYPE_INT, Fiddle::TYPE_INT, Fiddle::TYPE_UINT], Fiddle::TYPE_VOIDP) TryW a it = Fiddle::Function.new( LIBC['sem_tryw a it'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) W a it = Fiddle::Function.new( LIBC['sem_w a it'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) Post = Fiddle::Function.new( LIBC['sem_post'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) Close = Fiddle::Function.new( LIBC['sem_close'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) def report m, r = 0 puts "#{Time.now}: #{m}" if r != 0 e = Fiddle::l a st_error puts "terror = #{Errors[e]} [#{e}]" end end process 1 report "cre a ting sem a phore" s = Open.c a ll "/tmp/s", Fcntl::O_CREAT | Fcntl::O_RDWR, 777, 0 puts s.inspect report "sem a phore cre a ted" sleep 15 r = Post.c a ll s report "posted", r sleep 5 t = Time.now r = W a it.c a ll s report "w a ited #{Time.now - t} seconds", r r = Close.c a ll s report "sem a phore destroyed"
- 12. FFI foreign functions with Fiddle [Ruby 3.4] require ‘ f iddle’ require ‘fcntl’ LIBC = Fiddle::dlopen 'libc++.dylib' Open = Fiddle::Function.new( LIBC['sem_open'], [Fiddle::TYPE_CONST_STRING, Fiddle::TYPE_INT, Fiddle::TYPE_INT, Fiddle::TYPE_UINT], Fiddle::TYPE_VOIDP) TryW a it = Fiddle::Function.new( LIBC['sem_tryw a it'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) W a it = Fiddle::Function.new( LIBC['sem_w a it'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) Post = Fiddle::Function.new( LIBC['sem_post'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) Close = Fiddle::Function.new( LIBC['sem_close'], [Fiddle::TYPE_VOIDP], Fiddle::TYPE_INT) def report m, r = 0 puts "#{Time.now}: #{m}" if r != 0 e = Fiddle::l a st_error puts "terror = #{Errors[e]} [#{e}]" end end process 2 report "opening sem a phore" s = Open.c a ll "/tmp/s" puts s.inspect r = TryW a it.c a ll s report "locked" if r then report "busy", r t = Time.now r = W a it.c a ll s report "w a ited #{Time.now - t}s", r end sleep 10 report "posted", Post.c a ll(s)
- 13. [Ruby 1.9] require ‘dl’ memory_bu ff er = DL::m a lloc 20 => #<DL::PtrD a t a :0x2d0870 ptr=0x820600 size=20 free=0x1b0257> memory_bu ff er[0] = “hello world!” => “hello world!000000000000000000000000" memory_bu ff er.free => #<DL::Symbol:0x40b760 func=0x1b0257 'void (free)(void *);'> memory_bu ff er.nil => nil malloc = fun
- 14. [Ruby 1.9] string = “hello ruby” memory_bu ff er = string.to_ptr => #<DL::PtrD a t a :0x41be a 0 ptr=0x41be60 size=10 free=0x1b0257> memory_bu ff er[0] = “goodbye world” memory_bu ff er += 1 => #<DL::PtrD a t a :0x422000 ptr=0x41be61 size=9 free=0x0> puts memory_bu ff er, memory_bu ff er.to_str, string => “oodbye world” => “oodbye wo” => “hello ruby” memory_bu ff er -= 1 => (irb):51: [BUG] Segment a tion f a ult ...and frustration
- 15. [Ruby 1.9] Sign a l.tr a p(:SEGV) { $stderr.puts "segf a ult triggered" } Process.kill :SEGV, 0 $stderr.puts "but I c a rry on a s usu a l" require 'dl' memory = DL::m a lloc 1 4096.times { |i| memory[0] = 42.chr * i } $stderr.puts "even genuine segf a ults don't ph a se me" should produce: segf a ult triggered but I c a rry on a s usu a l but we can fi x that?
- 16. [Ruby 1.9] Sign a l.tr a p(:SEGV) { $stderr.puts "segf a ult triggered" } Process.kill :SEGV, 0 but we can fi x that? SIGSEGV in not a tr a pp a ble sign a l
- 17. [Ruby 3.4] Sign a l.tr a p(:SEGV) { $stderr.puts "segf a ult triggered" } Process.kill :SEGV, 0 but we can fi x that? a nd it prob a bly never will be
- 18. [Ruby 1.9] require 'dl' require ‘nevers a ydie’ memory = DL::m a lloc 1 4096.times do |i| begin puts "#{i} : #{(memory[1] = 42.chr * i).length}" rescue NeverS a yDie => e $stderr.puts "even genuine segf a ults don't ph a se me" bre a k end end produces: even genuine segf a ults don't ph a se me maybe with some tenderlove? wr a ps GNU libsigsegv a ctu a lly works
- 19. [Ruby 3.4] https://github.com/tenderlove/neversaydie gem inst a ll nevers a ydie maybe with some tenderlove? nevers a ydie doesn't build uses CONFIG r a ther th a n RbCon f ig
- 20. [Ruby 1.9] require 'dl' SIGSEGV = DL::dlopen('libsigsegv.dylib') inst a ll_h a ndler = SIGSEGV['sigsegv_inst a ll_h a ndler', 'IP'] deinst a ll_h a ndler = SIGSEGV['sigsegv_deinst a ll_h a ndler', '0'] le a ve_h a ndler = SIGSEGV['sigsegv_le a ve_h a ndler', 'IPPPP'] continu a tion = DL.c a llb a ck('IPPP') do | a ddress, b, c| r a ise RuntimeError, "segf a ult a t #{ a ddress}" end h a ndler = DL.c a llb a ck('IPI') do |f a ult_ a ddress, serious| le a ve_h a ndler.c a ll continu a tion, f a ult_ a ddress, nil, nil end inst a ll_h a ndler.c a ll h a ndler could this instead be done with DL?
- 21. [Ruby 1.9] require 'dl' SIGSEGV = DL::dlopen('libsigsegv.dylib') inst a ll_h a ndler = SIGSEGV['sigsegv_inst a ll_h a ndler', 'IP'] deinst a ll_h a ndler = SIGSEGV['sigsegv_deinst a ll_h a ndler', '0'] le a ve_h a ndler = SIGSEGV['sigsegv_le a ve_h a ndler', 'IPPPP'] continu a tion = DL.c a llb a ck('IPPP') do | a ddress, b, c| r a ise RuntimeError, "segf a ult a t #{ a ddress}" end h a ndler = DL.c a llb a ck('IPI') do |f a ult_ a ddress, serious| le a ve_h a ndler.c a ll continu a tion, f a ult_ a ddress, nil, nil end inst a ll_h a ndler.c a ll h a ndler could this instead be done with DL? NO!!!! the registered h a ndler is never c a lled
- 22. watch this space