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https://issues.apache.org/jira/browse/HADOOP-7147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13402848#comment-13402848
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Colin Patrick McCabe commented on HADOOP-7147:
----------------------------------------------
{code}
> int maxposix=sysconf(_SC_NGROUPS_MAX);
> gid_t *gps = (gid_t *) malloc(maxposix * sizeof (gid_t));
> if (!gps) {
> *ngroups = 0;
> free(pwbuf);
> return ENOMEM;
> }
...
{code}
Allocating an array of size _SC_NGROUPS_MAX seems a little excessive. I think
it would be better to use realloc() to expand an array of gid_t as needed.
{code}
// set the name of the group for subsequent calls to getnetgrent
// note that we want to end group lokup regardless whether setnetgrent
// was successful or not (as long as it was called we need to call
// endnetgrent)
setnetgrentCalledFlag = 1;
setnetgrent(cgroup); // some platforms return void here
UserList *current = NULL;
// three pointers are for host, user, domain, we only care
// about user now
char *p[3];
while(getnetgrent(p, p + 1, p + 2)) {
if(p[1]) {
current = (UserList *)malloc(sizeof(UserList));
current->string = malloc(strlen(p[1]) + 1);
strcpy(current->string, p[1]);
current->next = userListHead;
userListHead = current;
userListSize++;
}
}
// shortcut null, nonexistent groups
if (userListSize == 0)
goto END;
{code}
It seems like this should be extracted into a function which would just return
a linked list of UserList. There's no reason why the JNI function itself needs
to reference setgrent(), endnetgrent(), etc.
I'm also disturbed by the non-re-entrancy of the getnetgrent() function. It
seems like if we're going to use this function, we need to put a mutex around
it. Alternately, getnetgrent_r() is re-entrant, and available on Linux (but
not on some other platforms). You could do exactly the same thing you did here
and add this to the CMakeLists.txt:
{code}
CHECK_FUNCTION_EXISTS(getnetgrent_r HAVE_NETGRENT_R)
{code}
The uses of getnetgrent() need to be surrounded by a mutex, probably similar to
this:
{code}
static pthread_mutex_t g_getnetgrent_lock = PTHREAD_MUTEX_INITIALIZER;
UserList *get_net_groups(const char *name) {
pthread_mutex_lock(&lock);
... do non-thread-safe stuff ...
pthread_mutex_unlock(&lock);
}
{code}
> setnetgrent in native code is not portable
> ------------------------------------------
>
> Key: HADOOP-7147
> URL: https://issues.apache.org/jira/browse/HADOOP-7147
> Project: Hadoop Common
> Issue Type: Bug
> Components: native
> Affects Versions: 0.22.0, 0.23.0
> Reporter: Todd Lipcon
> Assignee: Allen Wittenauer
> Attachments: HADOOP-7147.patch, hadoop-7147.patch
>
>
> HADOOP-6864 uses the setnetgrent function in a way which is not compatible
> with BSD APIs, where the call returns void rather than int. This prevents the
> native libs from building on OSX, for example.
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