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Undefined behaviour when calling ioctl() multiple times

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#1,632 5 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
java
Domain
operating-systems

Research direction

Start with the LibC interface and getWindowSize() reproduction in the issue, then run the loop on the stated macOS, Apple M1, and GraalVM setup. Inspect how the winsize argument is represented and passed through JNA during repeated ioctl() calls. Done means repeated calls no longer return errors or terminate with SIGSEGV, illegal instructions, or heap corruption.

Written by the indexing model from the issue text.

Description

JNA version: 5.15.0
JVM: GraalVM CE 17.0.9+9.1 (build 17.0.9+9-jvmci-23.0-b22)
OS: macOS 14.7
CPU: Apple M1 (64-bit)

public interface LibC extends Library {
    LibC libC = Native.load("c", LibC.class);
    int TIOCGWINSZ = 0x40087468; // this is definitely correct, I've checked it with C
    
    int ioctl(int fd, int request, winsize winsize);  
}

public static int getWindowSize() {
    val ttysize = new winsize();

    val returnCode = libC.ioctl(0, TIOCGWINSZ, ttysize);
    if (returnCode != 0) {
        throw new RuntimeException("There was a problem calling ioctl(): " + returnCode);
    }

    return ttysize.ws_col;
}

 for (int i = 0; i < 100; i++) {
      System.out.println(getWindowSize());
}

running this code results in either:

  1. ioctl() returning -1
  2. SIGSEGV
  3. Illegal instruction: 4
  4. Heap corruption detected
Dominant language
Java
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