edwardcapriolo commented on PR #8177:
URL: https://github.com/apache/hadoop/pull/8177#issuecomment-3746776613
@cnauroth
Interestingly what I believe i have found is that your must deep copy these
objects. What I observe is repeated calls to the method changes the objects.
Something about the buffer sizing of the old code wasn't hitting the edge case.
For some confirmation I asked google: multipe callsto getpwnam_r to create
array of users.
It provided code that was doing a deep copy of the objects, and this
explanation.
Key Concepts
Reentrancy: getpwnam_r() is thread-safe because the caller provides the
memory (buffer) where the data is stored.
Persistent Storage: To build an array, you cannot just store pointers to
the temporary pwd struct used inside the loop. You must make a deep copy of the
data (the UserEntry struct and the strings within it) into a new, stable memory
location that persists across loop iterations.
Error Handling: Check the return value (status) and the result pointer
to differentiate between an error condition and a "user not found" scenario.
Memory Management: Dynamic memory allocation (malloc, strdup) requires
explicit deallocation using free to prevent memory leaks
This is exactly the conclusion I had come to that we need to deep copy this
object because the second call to the method alters the state of the first
struct.
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