6 ms·

If people use intmax_t and then they expect the ABI to stay stable, than they are at fault, not libc, LLVM or GCC for changing it when the actual "max int" chan

If people use intmax_t and then they expect the ABI to stay stable, than they are at fault, not libc, LLVM or GCC for changing it when the actual "max int" changes.

teddyh 4y ago
I feel the fault instead lies in the operating system for wanting to run old binaries so much that the operating system pretends that the system architecture (and associated ABI) has not changed, even when there exists larger integers than what the previous architecture had set as intmax_t.
- afiori 4y ago
  The problem is not old binaries, it is old code that assumes an upper bound to the size of intmax_t.
  - teddyh 4y ago
    I’m not sure what you mean. I agree that the problem is not the binaries, but I believe the problem to be the operating system. The source code may not have assumed a specific upper size limit on intmax_t, but the binaries were compiled in good faith to a specific machine architecture, which had a specific width on intmax_t, namely the largest integer type which that architecture could support. If then new CPU models come out with larger integer types, but the operating systems still runs that same binary straight up (without any emulation layer), this exposes the old binary to larger integer types, breaking the binary. The binary is not at fault, it’s the operating system which committed the sin of running the binary on what is effectively a different architecture without any considerations on what architecture the binary was actually compiled for.
    - afiori 4y ago
      The OS could do this for old binaries but no for old source. A lot of FOSS code has baked in assumptions about the max size of intmax_t and the compiler and the OS cannot do much about broken logic.
      - teddyh 4y ago
        > A lot of FOSS code has baked in assumptions about the max size of intmax_t Well, that code is not, and was not ever, standards compliant.
        shadowgovt 4y ago
        And it turns out that doesn't matter much in terms of adoption and popularity. After all, if predictable behavior in the future across all possible configurations were a high priority requirement for the tools people use to make computers do things, neither C nor C++ would have gotten off the ground. Instead, people don't memorize the entire standard. They write code that works on their machine, publish it, fix the bugs when people say it doesn't work on their machine, and maybe converge towards something that is standards compliant but, more likely, they converge towards something that works on the standard implementation on 90% of the operating systems available.
      - kazinator 4y ago
        > A lot of FOSS code has baked in assumptions about the max size of intmax_t Would you be able to name three examples?
        afiori 4y ago
        I realize I used FOSS improperly, I had no reason to single it out; my comment reads like a critique of open source which was not my intention. My intention was to make a good case for old code being compiled today by third parties. But to my understanding intmax_t was introduced in C99, before widespread dominance of 64 bits platforms. So it would not be surprising that there exists code with lower assumptions about its size. But actually I made also another mistake, the major problem had little to do with faulty logic and more to do with dynamic linking [0] I will see myself out today. [0] https://thephd.dev/intmax_t-hell-c++-c https://thephd.dev/intmax_t-hell-c++-c
pdw 4y ago
But all major C compilers promise that they won't make ABI changes. So I'd rather say that standardizing intmax_t was a mistake.
- kazinator 4y ago
  If you don't standardize intmax_t, programs will invent the concept for themselves through some combination of preprocessing directives and shell scripts that probe the toolchain. If you want to know "what is the widest signed integer type available", you will get some kind of answer one way or another.
  - mtlmtlmtlmtl 4y ago
    Or even worse, if they don't know their build tools, some kind of union based monstrosity...
- kevin_thibedeau 4y ago
  GCC changed long to 64-bits and x86 codebases had to accept that. The base integer types are designed to be variable sized and you code accordingly based on the minimum size guarantee. Assuming types are frozen in time is how you get things like LLP64.
  - klodolph 4y ago
    Long is 32 bits on x86, 64 bits on x86_64. x86 code bases broke because they made non-portable assumptions.
    - kevin_thibedeau 4y ago
      No. It's 32-bits minimum. It can be anything larger. That's what the language says. Assuming otherwise is nonportable.
      - deleted 4y ago
        [deleted]

If people use intmax_t and then they expect the ABI to stay stable, than they are at fault, not libc, LLVM or GCC for changing it when the actual "max int" changes.

teddyh 4y ago

I feel the fault instead lies in the operating system for wanting to run old binaries so much that the operating system pretends that the system architecture (and associated ABI) has not changed, even when there exists larger integers than what the previous architecture had set as intmax_t.

afiori 4y ago
The problem is not old binaries, it is old code that assumes an upper bound to the size of intmax_t.
- teddyh 4y ago
  I’m not sure what you mean. I agree that the problem is not the binaries, but I believe the problem to be the operating system. The source code may not have assumed a specific upper size limit on intmax_t, but the binaries were compiled in good faith to a specific machine architecture, which had a specific width on intmax_t, namely the largest integer type which that architecture could support. If then new CPU models come out with larger integer types, but the operating systems still runs that same binary straight up (without any emulation layer), this exposes the old binary to larger integer types, breaking the binary. The binary is not at fault, it’s the operating system which committed the sin of running the binary on what is effectively a different architecture without any considerations on what architecture the binary was actually compiled for.
  - afiori 4y ago
    The OS could do this for old binaries but no for old source. A lot of FOSS code has baked in assumptions about the max size of intmax_t and the compiler and the OS cannot do much about broken logic.
    - teddyh 4y ago
      > A lot of FOSS code has baked in assumptions about the max size of intmax_t Well, that code is not, and was not ever, standards compliant.
      - shadowgovt 4y ago
        And it turns out that doesn't matter much in terms of adoption and popularity. After all, if predictable behavior in the future across all possible configurations were a high priority requirement for the tools people use to make computers do things, neither C nor C++ would have gotten off the ground. Instead, people don't memorize the entire standard. They write code that works on their machine, publish it, fix the bugs when people say it doesn't work on their machine, and maybe converge towards something that is standards compliant but, more likely, they converge towards something that works on the standard implementation on 90% of the operating systems available.
    - kazinator 4y ago
      > A lot of FOSS code has baked in assumptions about the max size of intmax_t Would you be able to name three examples?
      - afiori 4y ago
        I realize I used FOSS improperly, I had no reason to single it out; my comment reads like a critique of open source which was not my intention. My intention was to make a good case for old code being compiled today by third parties. But to my understanding intmax_t was introduced in C99, before widespread dominance of 64 bits platforms. So it would not be surprising that there exists code with lower assumptions about its size. But actually I made also another mistake, the major problem had little to do with faulty logic and more to do with dynamic linking [0] I will see myself out today. [0] https://thephd.dev/intmax_t-hell-c++-c https://thephd.dev/intmax_t-hell-c++-c

pdw 4y ago

But all major C compilers promise that they won't make ABI changes. So I'd rather say that standardizing intmax_t was a mistake.

kazinator 4y ago
If you don't standardize intmax_t, programs will invent the concept for themselves through some combination of preprocessing directives and shell scripts that probe the toolchain. If you want to know "what is the widest signed integer type available", you will get some kind of answer one way or another.
- mtlmtlmtlmtl 4y ago
  Or even worse, if they don't know their build tools, some kind of union based monstrosity...
kevin_thibedeau 4y ago
GCC changed long to 64-bits and x86 codebases had to accept that. The base integer types are designed to be variable sized and you code accordingly based on the minimum size guarantee. Assuming types are frozen in time is how you get things like LLP64.
- klodolph 4y ago
  Long is 32 bits on x86, 64 bits on x86_64. x86 code bases broke because they made non-portable assumptions.
  - kevin_thibedeau 4y ago
    No. It's 32-bits minimum. It can be anything larger. That's what the language says. Assuming otherwise is nonportable.
    - deleted 4y ago
      [deleted]