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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
    #15

    @rygorous @regehr Petition to rename to -fun-math.

    1 Reply Last reply
    0
    • 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.

      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
        #17

        @rygorous

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

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

        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/

          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?

                    1 Reply Last reply
                    0
                    • 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

                            1 Reply Last reply
                            0
                            • 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.

                                  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/

                                    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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