如何按给定Git Diff修改OpenBSD的arc4random.c代码？

First, let's break down what your existing Git diff is doing:

diff --git openbsd-compat/arc4random.c openbsd-compat/arc4random.c
--- openbsd-compat/arc4random.c
+++ openbsd-compat/arc4random.c
@@ -242,7 +242,7 @@ void arc4random_buf(void *buf, size_t n) {
_ARC4_LOCK();

• _rs_random_buf(buf, n);
  

• memset(buf, 0, n);
    _ARC4_UNLOCK();
  

}

endif /* !HAVE_ARC4RANDOM_BUF */ #

This diff replaces the call to _rs_random_buf() with memset() to zero out the buffer instead of filling it with random data, within the arc4random_buf() function that's compiled when HAVE_ARC4RANDOM_BUF is not defined.

Here's how to replicate this change in the OpenBSD src repository's lib/libc/crypt/arc4random.c:

• Step 1: Locate the target function
  Open the lib/libc/crypt/arc4random.c file and find the arc4random_buf() function wrapped in the #endif /* !HAVE_ARC4RANDOM_BUF */ block. Look for the code section that includes:

  void arc4random_buf(void *buf, size_t n) {
          _ARC4_LOCK();
          _rs_random_buf(buf, n);
          _ARC4_UNLOCK();
  }
  # endif /* !HAVE_ARC4RANDOM_BUF */
  

• Step 2: Modify the line inside the lock/unlock block
  Replace the line _rs_random_buf(buf, n); with memset(buf, 0, n);. Your modified code should look like this:

  void arc4random_buf(void *buf, size_t n) {
          _ARC4_LOCK();
          memset(buf, 0, n);
          _ARC4_UNLOCK();
  }
  # endif /* !HAVE_ARC4RANDOM_BUF */
  

• Step 3: Verify the context
  Double-check that you're modifying the correct instance of arc4random_buf()—it should be the one guarded by the !HAVE_ARC4RANDOM_BUF preprocessor condition, and surrounded by the _ARC4_LOCK() and _ARC4_UNLOCK() calls to ensure thread safety (just like in your original diff).

That's it! This change will match exactly what your Git diff specifies.

内容的提问来源于stack exchange，提问作者Hessnov