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  3. I guess people are just going to keep discovering that you can't really make a C compiler do constant time

I guess people are just going to keep discovering that you can't really make a C compiler do constant time

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  • Per VognsenP This user is from outside of this forum
    Per VognsenP This user is from outside of this forum
    Per Vognsen
    wrote last edited by
    #16

    @rygorous @regehr -fhonor-yahweh -fhonor-buddha -fhonor-brahma just to be safe. You need all the help you can get with -ffast-math.

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    0
    • John RegehrR This user is from outside of this forum
      John RegehrR This user is from outside of this forum
      John Regehr
      wrote last edited by
      #17

      @rygorous

      well, if the problems are important enough, something like this:

      https://discourse.llvm.org/t/rfc-constant-time-coding-support/87781

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      0
      • John RegehrR John Regehr

        I guess people are just going to keep discovering that you can't really make a C compiler do constant time

        https://www.theregister.com/2026/02/09/compilers_undermine_encryption/

        kaoudisK This user is from outside of this forum
        kaoudisK This user is from outside of this forum
        kaoudis
        wrote last edited by
        #18

        @regehr all I will say to that is eyup

        John RegehrR 1 Reply Last reply
        0
        • John RegehrR This user is from outside of this forum
          John RegehrR This user is from outside of this forum
          John Regehr
          wrote last edited by
          #19

          @rygorous @pervognsen aw, look at all the little nans and infs flying and being free!!!

          Per VognsenP 1 Reply Last reply
          0
          • kaoudisK kaoudis

            @regehr all I will say to that is eyup

            John RegehrR This user is from outside of this forum
            John RegehrR This user is from outside of this forum
            John Regehr
            wrote last edited by
            #20

            @kaoudis I've not been paying too much attention to the LLVM effort-- anything interesting going on there? or should I just dig into the discourse?

            kaoudisK 1 Reply Last reply
            0
            • John RegehrR John Regehr

              @rygorous @pervognsen aw, look at all the little nans and infs flying and being free!!!

              Per VognsenP This user is from outside of this forum
              Per VognsenP This user is from outside of this forum
              Per Vognsen
              wrote last edited by
              #21

              @regehr @rygorous My first thought was, if this is meant for the far future, assuming they retain our current warning symbol for radiation seems a bit hopeful.

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              • John RegehrR John Regehr

                @kaoudis I've not been paying too much attention to the LLVM effort-- anything interesting going on there? or should I just dig into the discourse?

                kaoudisK This user is from outside of this forum
                kaoudisK This user is from outside of this forum
                kaoudis
                wrote last edited by
                #22

                @regehr I think* @wizardengineer landed the first bits of that work!

                *I left trail of bits voluntarily (and for reasons unrelated) a bit before this happened though

                John RegehrR 1 Reply Last reply
                0
                • Janne MorenJ This user is from outside of this forum
                  Janne MorenJ This user is from outside of this forum
                  Janne Moren
                  wrote last edited by
                  #23

                  @rygorous @regehr
                  Rename to -ffast-bad-math perhaps?

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                  • kaoudisK kaoudis

                    @regehr I think* @wizardengineer landed the first bits of that work!

                    *I left trail of bits voluntarily (and for reasons unrelated) a bit before this happened though

                    John RegehrR This user is from outside of this forum
                    John RegehrR This user is from outside of this forum
                    John Regehr
                    wrote last edited by
                    #24

                    @kaoudis @wizardengineer ah! I don't think I knew that. where are you at right now?

                    kaoudisK 1 Reply Last reply
                    0
                    • Janne MorenJ This user is from outside of this forum
                      Janne MorenJ This user is from outside of this forum
                      Janne Moren
                      wrote last edited by
                      #25

                      @rygorous @regehr
                      -flooks-like-math-if-you-squint

                      1 Reply Last reply
                      0
                      • John RegehrR John Regehr

                        I guess people are just going to keep discovering that you can't really make a C compiler do constant time

                        https://www.theregister.com/2026/02/09/compilers_undermine_encryption/

                        William D. JonesC This user is from outside of this forum
                        William D. JonesC This user is from outside of this forum
                        William D. Jones
                        wrote last edited by
                        #26

                        @regehr Maybe it's time to write new assemblers that complement NASM*.

                        * Or MASM; I wish NASM had an invoke keyword, like MASM, to abstract away calling conventions. Rather than writing a macro for it.

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                        • Andy GockeA This user is from outside of this forum
                          Andy GockeA This user is from outside of this forum
                          Andy Gocke
                          wrote last edited by
                          #27

                          @rygorous @regehr We've had a hell of a time with our macos ARM64 ASM. Last ~3 ld64 updates have all had reloc problems

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                          • John RegehrR John Regehr

                            @kaoudis @wizardengineer ah! I don't think I knew that. where are you at right now?

                            kaoudisK This user is from outside of this forum
                            kaoudisK This user is from outside of this forum
                            kaoudis
                            wrote last edited by
                            #28

                            @regehr @wizardengineer Strava! I’m doing appsec over there

                            John RegehrR 1 Reply Last reply
                            0
                            • kaoudisK kaoudis

                              @regehr @wizardengineer Strava! I’m doing appsec over there

                              John RegehrR This user is from outside of this forum
                              John RegehrR This user is from outside of this forum
                              John Regehr
                              wrote last edited by
                              #29

                              @kaoudis @wizardengineer awesome!

                              1 Reply Last reply
                              0
                              • John RegehrR John Regehr

                                I guess people are just going to keep discovering that you can't really make a C compiler do constant time

                                https://www.theregister.com/2026/02/09/compilers_undermine_encryption/

                                Pierre H.M This user is from outside of this forum
                                Pierre H.M This user is from outside of this forum
                                Pierre H.
                                wrote last edited by
                                #30

                                @regehr yes you can, unless you care about correct results too.

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                                0
                                • John RegehrR John Regehr

                                  I guess people are just going to keep discovering that you can't really make a C compiler do constant time

                                  https://www.theregister.com/2026/02/09/compilers_undermine_encryption/

                                  Tor LillqvistT This user is from outside of this forum
                                  Tor LillqvistT This user is from outside of this forum
                                  Tor Lillqvist
                                  wrote last edited by
                                  #31

                                  @regehr "The user types in a password, which gets checked against a database, character by character"

                                  Seriously? That is how they think it works?

                                  1 Reply Last reply
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