Skip to content
  • Home Home Home, current page.
  • Moments Moments Moments, current page.

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @
  • Language: English
    • Bahasa Indonesia
    • Bahasa Melayu
    • Català
    • Čeština
    • Dansk
    • Deutsch
    • English UK
    • Español
    • Filipino
    • Français
    • Hrvatski
    • Italiano
    • Magyar
    • Nederlands
    • Norsk
    • Polski
    • Português
    • Română
    • Slovenčina
    • Suomi
    • Svenska
    • Tiếng Việt
    • Türkçe
    • Ελληνικά
    • Български език
    • Русский
    • Српски
    • Українська мова
    • עִבְרִית
    • العربية
    • فارسی
    • मराठी
    • हिन्दी
    • বাংলা
    • ગુજરાતી
    • தமிழ்
    • ಕನ್ನಡ
    • ภาษาไทย
    • 한국어
    • 日本語
    • 简体中文
    • 繁體中文
  • Have an account? Log in
    Have an account?
    · Forgot password?

    New to Twitter?
    Sign up
RichFelker's profile
Rich Felker
Rich Felker
Rich Felker
@RichFelker

Tweets

Rich Felker

@RichFelker

Yeah, I do @musllibc, FOSS & infosec stuff. But now is not the time for a mostly-/only-tech Twitter feed.

musl-libc.org
Joined March 2014

Tweets

  • © 2018 Twitter
  • About
  • Help Center
  • Terms
  • Privacy policy
  • Cookies
  • Ads info
Dismiss
Previous
Next

Go to a person's profile

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @

Promote this Tweet

Block

  • Tweet with a location

    You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more

    Your lists

    Create a new list


    Under 100 characters, optional

    Privacy

    Copy link to Tweet

    Embed this Tweet

    Embed this Video

    Add this Tweet to your website by copying the code below. Learn more

    Add this video to your website by copying the code below. Learn more

    Hmm, there was a problem reaching the server.

    By embedding Twitter content in your website or app, you are agreeing to the Twitter Developer Agreement and Developer Policy.

    Preview

    Why you're seeing this ad

    Log in to Twitter

    · Forgot password?
    Don't have an account? Sign up »

    Sign up for Twitter

    Not on Twitter? Sign up, tune into the things you care about, and get updates as they happen.

    Sign up
    Have an account? Log in »

    Two-way (sending and receiving) short codes:

    Country Code For customers of
    United States 40404 (any)
    Canada 21212 (any)
    United Kingdom 86444 Vodafone, Orange, 3, O2
    Brazil 40404 Nextel, TIM
    Haiti 40404 Digicel, Voila
    Ireland 51210 Vodafone, O2
    India 53000 Bharti Airtel, Videocon, Reliance
    Indonesia 89887 AXIS, 3, Telkomsel, Indosat, XL Axiata
    Italy 4880804 Wind
    3424486444 Vodafone
    » See SMS short codes for other countries

    Confirmation

     

    Welcome home!

    This timeline is where you’ll spend most of your time, getting instant updates about what matters to you.

    Tweets not working for you?

    Hover over the profile pic and click the Following button to unfollow any account.

    Say a lot with a little

    When you see a Tweet you love, tap the heart — it lets the person who wrote it know you shared the love.

    Spread the word

    The fastest way to share someone else’s Tweet with your followers is with a Retweet. Tap the icon to send it instantly.

    Join the conversation

    Add your thoughts about any Tweet with a Reply. Find a topic you’re passionate about, and jump right in.

    Learn the latest

    Get instant insight into what people are talking about now.

    Get more of what you love

    Follow more accounts to get instant updates about topics you care about.

    Find what's happening

    See the latest conversations about any topic instantly.

    Never miss a Moment

    Catch up instantly on the best stories happening as they unfold.

    Rich Felker‏ @RichFelker Mar 4

    Evil proposed compiler optimization: in __attribute(__pure__)__ functions, optimize malloc(n) to 0.

    5:56 PM - 4 Mar 2018
    • 6 Likes
    • Justin Cormack drxzcl Jon Roelofs William Pitcock Daniel Bittman Steve Canon
    2 replies 0 retweets 6 likes
      1. Rich Felker‏ @RichFelker Mar 4

        Expanded: optimize any call to a known-impure function to a random valid return value for it, assuming the caller must produce same result regardless.

        0 replies 0 retweets 0 likes
        Show this thread
        Thanks. Twitter will use this to make your timeline better. Undo
        Undo
      1. New conversation
      2. Tor Myklebust‏ @t2mykleb Mar 5
        Replying to @RichFelker

        Why would this be valid? Gcc docs only say that __attr__((pure)) functions must have no effects except the return value, and return value depends only on params and global variables. Compiler cannot prove that malloc might fail during an __attr__((pure)) function call.

        1 reply 0 retweets 0 likes
      3. Rich Felker‏ @RichFelker Mar 5
        Replying to @t2mykleb

        Indeed gcc's definition allows global reads so it's questionable. I was thinking something in between gcc's pure & const. Surely the optimization is valid for const though.

        2 replies 0 retweets 0 likes
      4. Rich Felker‏ @RichFelker Mar 5
        Replying to @RichFelker @t2mykleb

        If the function is attr-const it must return the same thing it would if called in a context where malloc would fail.

        1 reply 0 retweets 0 likes
      5. Tor Myklebust‏ @t2mykleb Mar 5
        Replying to @RichFelker

        What if no such context occurs in my program?

        1 reply 0 retweets 0 likes
      6. Rich Felker‏ @RichFelker Mar 5
        Replying to @t2mykleb

        It's not under the program's control. Aside from necessarily failing after somewhere on the order of 2^(CHAR_BIT*sizeof(void*)) objects are in existence, it's up to the implementation if/when malloc fails. There is no context where it "can't fail".

        1 reply 0 retweets 0 likes
      7. Tor Myklebust‏ @t2mykleb Mar 5
        Replying to @RichFelker

        The program is under no obligation to attempt to create so many objects simultaneously. Even if it did so, it's under no obligation to call that __attr__((const)) function in such a state.

        2 replies 0 retweets 0 likes
      8. Rich Felker‏ @RichFelker Mar 5
        Replying to @t2mykleb

        I think you misread. The point was that under extreme conditions the implementations is forced to make malloc fail, but it's never forced to make it succeed. Failure is always an option.

        2 replies 0 retweets 0 likes
      9. Rich Felker‏ @RichFelker Mar 5
        Replying to @RichFelker @t2mykleb

        In particular on any implementation where the invoking user can control resource limits, it's always possible for any particular call to malloc to fail.

        1 reply 0 retweets 0 likes
      10. 11 more replies

    Loading seems to be taking a while.

    Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.

      Promoted Tweet

      false

      • © 2018 Twitter
      • About
      • Help Center
      • Terms
      • Privacy policy
      • Cookies
      • Ads info