5 ms·

When I was a kid, I always suspected a compiler or CPU bug when my program did not behave as expected. I heard similar stories on more than several occasions fr

When I was a kid, I always suspected a compiler or CPU bug when my program did not behave as expected. I heard similar stories on more than several occasions from other people, so being naïve must be a common thing among us software engineers when we make our first steps. Kudos to Mozilla, their finding is a real CPU bug.

pengaru 3y ago
For ages in *nixland the phrase "select is not broken" has been an aphorism for such situations. I'm not sure of its origin, but it's referenced in The Pragmatic Programmer: > Tip #33, pg. 95: > > “select” Isn't Broken > > It is rare to find a bug in the OS or the compiler, or even a third-party > product or library. The bug is most likely in the application.
- AshamedCaptain 3y ago
  I really don't know when this became "common knowledge". Most OSes and compilers were utter crap not more than 10-20 years ago. We would spend afternoons ranting about MSVC++ bugs. gcc was a joke, and even if quickly improved, does nobody really remember that by the 2010's gcc was so buggy -O3 was barely usable? No Gentoo users around?
  - RetroTechie 3y ago
    I recall doing some Gentoo installs using -Os at least for some packages, just to see how much that would shrink binary sizes. Documentation / wikis etc. advised against that not just for performance-of-generated-code reasons, but also because of compiler bugs using -Os was considered unreliable. Note this was with ancient GCC (v2.9.x, early 3.x releases iirc)
  - paulddraper 3y ago
    `-O3` was known/documented to be unsafe.
- toast0 3y ago
  Yeah, I don't know where that comes from. Everything is broken. If you think select is broken, read the docs and make sure you're using it correctly. If you still think select isn't doing what the docs say, try to reduce your actual use into a minimal test case and see. Go look at the source for select on your OS. Search the internet and see if anyone else ran into the same thing (but be careful, because there's lots of bad leads out there).
- syncsynchalt 3y ago
  Ironically we later found that `select` is broken by design. `poll` was created as an improvement, and syscalls like `epoll` later refined it further.
  - pengaru 3y ago
    FD_SETSIZE ought to be enough for anybody
mastax 3y ago
If you step into microcontroller land you run into hardware bugs all the time, at least if you have to write any low-level code. My very first major project I ran into at least 3 silicon bugs which wasted weeks of my life. Rookie mistake: check the errata. Though one of the bugs wasn't in the errata.
0xffff2 3y ago
It's a good guideline when you're early on in your programming career, but I've been surprised by how many compiler bugs I have independently re-discovered in my career. One of the curses of my job is that I work with ancient compilers. About half a dozen times I have stumbled on a bug, spent the better part of a day debugging my code, only to find that I'm being bitten by a documented GCC bug that was fixed a decade ago.
- IshKebab 3y ago
  One of the big reasons to keep software up to date IMO.
  - mort96 3y ago
    Not that easy when you have to use some vendor's SDK which includes some forked GCC 4.x...
dkarras 3y ago
yeah same, from almost 30 years ago. Interesting shift. I distinctly remember having the instinct that it must be the computer that must be wrong, and what I wrote was obviously correct. Thanks for reminding me of that. With some experience, you figure out that you are wrong %99.99 of the time and after that loop, the thought never crosses your mind. I've never had to deal with hardware bugs myself, but had my share of compiler and platform bugs over the years.
londons_explore 3y ago
It's not a real CPU bug unless you can write a 20 line program in C/assembly and run it to demonstrate the problem. Then, when you've done that, send it to samsung so they patch it in their CPU design. They may even be able to patch it in their devices in the field (it's common for CPU designs to have special hardware whose purpose is runtime detecting certain trigger conditions and running replacement code to avoid hardware bugs discovered after the CPU was produced). They can also issue an errata which might let compiler authors modify their code generators to avoid any pattern that triggers the bug, therefore avoiding other projects being impacted.
bpye 3y ago
There are a surprising (or unsurprising depending on your perspective) number of hardware bugs out there. There are published errata that I had hit before they were documented. It’s not always very much fun - and leads to a lot of head scratching.

pengaru 3y ago

For ages in *nixland the phrase "select is not broken" has been an aphorism for such situations. I'm not sure of its origin, but it's referenced in The Pragmatic Programmer: > Tip #33, pg. 95: > > “select” Isn't Broken > > It is rare to find a bug in the OS or the compiler, or even a third-party > product or library. The bug is most likely in the application.

AshamedCaptain 3y ago
I really don't know when this became "common knowledge". Most OSes and compilers were utter crap not more than 10-20 years ago. We would spend afternoons ranting about MSVC++ bugs. gcc was a joke, and even if quickly improved, does nobody really remember that by the 2010's gcc was so buggy -O3 was barely usable? No Gentoo users around?
- RetroTechie 3y ago
  I recall doing some Gentoo installs using -Os at least for some packages, just to see how much that would shrink binary sizes. Documentation / wikis etc. advised against that not just for performance-of-generated-code reasons, but also because of compiler bugs using -Os was considered unreliable. Note this was with ancient GCC (v2.9.x, early 3.x releases iirc)
- paulddraper 3y ago
  `-O3` was known/documented to be unsafe.
toast0 3y ago
Yeah, I don't know where that comes from. Everything is broken. If you think select is broken, read the docs and make sure you're using it correctly. If you still think select isn't doing what the docs say, try to reduce your actual use into a minimal test case and see. Go look at the source for select on your OS. Search the internet and see if anyone else ran into the same thing (but be careful, because there's lots of bad leads out there).
syncsynchalt 3y ago
Ironically we later found that `select` is broken by design. `poll` was created as an improvement, and syscalls like `epoll` later refined it further.
- pengaru 3y ago
  FD_SETSIZE ought to be enough for anybody

mastax 3y ago

If you step into microcontroller land you run into hardware bugs all the time, at least if you have to write any low-level code. My very first major project I ran into at least 3 silicon bugs which wasted weeks of my life. Rookie mistake: check the errata. Though one of the bugs wasn't in the errata.

0xffff2 3y ago

It's a good guideline when you're early on in your programming career, but I've been surprised by how many compiler bugs I have independently re-discovered in my career. One of the curses of my job is that I work with ancient compilers. About half a dozen times I have stumbled on a bug, spent the better part of a day debugging my code, only to find that I'm being bitten by a documented GCC bug that was fixed a decade ago.

IshKebab 3y ago
One of the big reasons to keep software up to date IMO.
- mort96 3y ago
  Not that easy when you have to use some vendor's SDK which includes some forked GCC 4.x...

dkarras 3y ago

yeah same, from almost 30 years ago. Interesting shift. I distinctly remember having the instinct that it must be the computer that must be wrong, and what I wrote was obviously correct. Thanks for reminding me of that. With some experience, you figure out that you are wrong %99.99 of the time and after that loop, the thought never crosses your mind. I've never had to deal with hardware bugs myself, but had my share of compiler and platform bugs over the years.

londons_explore 3y ago

It's not a real CPU bug unless you can write a 20 line program in C/assembly and run it to demonstrate the problem. Then, when you've done that, send it to samsung so they patch it in their CPU design. They may even be able to patch it in their devices in the field (it's common for CPU designs to have special hardware whose purpose is runtime detecting certain trigger conditions and running replacement code to avoid hardware bugs discovered after the CPU was produced). They can also issue an errata which might let compiler authors modify their code generators to avoid any pattern that triggers the bug, therefore avoiding other projects being impacted.

bpye 3y ago

There are a surprising (or unsurprising depending on your perspective) number of hardware bugs out there. There are published errata that I had hit before they were documented. It’s not always very much fun - and leads to a lot of head scratching.