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  4. What the hell gcc?

What the hell gcc?

Scheduled Pinned Locked Moved The Weird and The Wonderful
designcomgraphicsiot
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  • K k5054

    The issue would arise if the size of a float is less than the size of a pointer. Maybe just ask the compiler to what sizeof(float) and sizeof(void*) return?

    "A little song, a little dance, a little seltzer down your pants" Chuckles the clown

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    honey the codewitch
    wrote on last edited by
    #14

    Thanks. I'll look into it as time and motivation allows. :) Edit: Turns out i had a project open so it was easy enough to check

    sizeof(float): 4
    sizeof(long*): 4

    I checked sizeof long* just to be certain

    Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

    K 1 Reply Last reply
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    • H honey the codewitch

      Thanks. I'll look into it as time and motivation allows. :) Edit: Turns out i had a project open so it was easy enough to check

      sizeof(float): 4
      sizeof(long*): 4

      I checked sizeof long* just to be certain

      Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

      K Offline
      K Offline
      k5054
      wrote on last edited by
      #15

      Well, not that then :( Seemed like a good answer at the time. Maybe it's just the type punning that's baffling the compiler?

      "A little song, a little dance, a little seltzer down your pants" Chuckles the clown

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      • K k5054

        Well, not that then :( Seemed like a good answer at the time. Maybe it's just the type punning that's baffling the compiler?

        "A little song, a little dance, a little seltzer down your pants" Chuckles the clown

        H Offline
        H Offline
        honey the codewitch
        wrote on last edited by
        #16

        That's my theory, but I'm uncomfortable with it if nothing else because a) I hate assuming compiler bugs. So often it's some effing intricacy of the C or C++ language that is at play, rather than the compiler in error. b) You'd think it would have been found and fixed. Like I said, this isn't the first time I've run into it. The last time was a lot more innocuous - no type aliasing or fudging like that. it was an enum struct type declared as a local variable and initialized at declaration time. :confused: :rolleyes: I'd dig up the old example if i could, but I ended up working around it in order to get the warnings out of my code without using compiler specific pragmas. Edit: Duh. I am not using the latest GCC. I didn't think about that. Could easily be a bug.

        Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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        • H honey the codewitch

          That's my theory, but I'm uncomfortable with it if nothing else because a) I hate assuming compiler bugs. So often it's some effing intricacy of the C or C++ language that is at play, rather than the compiler in error. b) You'd think it would have been found and fixed. Like I said, this isn't the first time I've run into it. The last time was a lot more innocuous - no type aliasing or fudging like that. it was an enum struct type declared as a local variable and initialized at declaration time. :confused: :rolleyes: I'd dig up the old example if i could, but I ended up working around it in order to get the warnings out of my code without using compiler specific pragmas. Edit: Duh. I am not using the latest GCC. I didn't think about that. Could easily be a bug.

          Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

          K Offline
          K Offline
          k5054
          wrote on last edited by
          #17

          I get the same warning with gcc-14.1.0, and with x86-64 gcc-trunk over at the compiler explorer, so it's not been fixed so far.

          "A little song, a little dance, a little seltzer down your pants" Chuckles the clown

          H 1 Reply Last reply
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          • H honey the codewitch

            That's my theory, but I'm uncomfortable with it if nothing else because a) I hate assuming compiler bugs. So often it's some effing intricacy of the C or C++ language that is at play, rather than the compiler in error. b) You'd think it would have been found and fixed. Like I said, this isn't the first time I've run into it. The last time was a lot more innocuous - no type aliasing or fudging like that. it was an enum struct type declared as a local variable and initialized at declaration time. :confused: :rolleyes: I'd dig up the old example if i could, but I ended up working around it in order to get the warnings out of my code without using compiler specific pragmas. Edit: Duh. I am not using the latest GCC. I didn't think about that. Could easily be a bug.

            Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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            Rick York
            wrote on last edited by
            #18

            As far as I am concerned, the fact that you have this line :

            float y     = x;
            

            which is clearly initializing the variable qualifies it as a bug. I can not conceive a situation where that is not a bug.

            "They have a consciousness, they have a life, they have a soul! Damn you! Let the rabbits wear glasses! Save our brothers! Can I get an amen?"

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            • K k5054

              I get the same warning with gcc-14.1.0, and with x86-64 gcc-trunk over at the compiler explorer, so it's not been fixed so far.

              "A little song, a little dance, a little seltzer down your pants" Chuckles the clown

              H Offline
              H Offline
              honey the codewitch
              wrote on last edited by
              #19

              I didn't think of trying godbolt. I'm really distracted rn on the phone w/ an old friend.

              Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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              • H honey the codewitch

                That's my theory, but I'm uncomfortable with it if nothing else because a) I hate assuming compiler bugs. So often it's some effing intricacy of the C or C++ language that is at play, rather than the compiler in error. b) You'd think it would have been found and fixed. Like I said, this isn't the first time I've run into it. The last time was a lot more innocuous - no type aliasing or fudging like that. it was an enum struct type declared as a local variable and initialized at declaration time. :confused: :rolleyes: I'd dig up the old example if i could, but I ended up working around it in order to get the warnings out of my code without using compiler specific pragmas. Edit: Duh. I am not using the latest GCC. I didn't think about that. Could easily be a bug.

                Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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                0x01AA
                wrote on last edited by
                #20

                Quote:

                I hate assuming compiler bugs

                No, it is definitely not a compiler bug. It is a defined behaviour, there are lots of documents in www which explain the background.

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                • 0 0x01AA

                  Quote:

                  I hate assuming compiler bugs

                  No, it is definitely not a compiler bug. It is a defined behaviour, there are lots of documents in www which explain the background.

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                  honey the codewitch
                  wrote on last edited by
                  #21

                  0x01AA wrote:

                  It is a defined behaviour

                  That's precisely what I was afraid of. :~

                  Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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                  • H honey the codewitch

                    0x01AA wrote:

                    It is a defined behaviour

                    That's precisely what I was afraid of. :~

                    Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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                    0x01AA
                    wrote on last edited by
                    #22

                    In a message above, you mentioned, there is no std available. But maybe in your environement some kind of bit_cast is available? If not, I think a similar behaviour (to inform the compiler [optimizer]) can be achived with reinterpret_cast, but at the moment I don't remember the document, from where I got this :( Sorry, for my strange English ...

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                    • 0 0x01AA

                      In a message above, you mentioned, there is no std available. But maybe in your environement some kind of bit_cast is available? If not, I think a similar behaviour (to inform the compiler [optimizer]) can be achived with reinterpret_cast, but at the moment I don't remember the document, from where I got this :( Sorry, for my strange English ...

                      H Offline
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                      honey the codewitch
                      wrote on last edited by
                      #23

                      It's possible I could do it with reinterpret_cast? I dunno

                      Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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                      • H honey the codewitch

                        It's possible I could do it with reinterpret_cast? I dunno

                        Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

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                        0x01AA
                        wrote on last edited by
                        #24

                        Try it ;) I think it simply informs the compiler 'you are aware' about a maybe not safe conversion ...

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