init: clamp fd limits to int

When setting the fd limit to 1 >> 31, the node fails to start:

ulimit -n 214748364
build/bin/bitcoind
Error: Not enough file descriptors available. -2147483648 available, 160 required.

Similar to the previous commit, this is fixed by capping the limit
to std::numeric_limits<int>::max().

Author: Sjors

src/util/fs_helpers.cpp

@@ -158,10 +158,12 @@ int RaiseFileDescriptorLimit(int min_fd)
 #else
     struct rlimit limitFD;
     if (getrlimit(RLIMIT_NOFILE, &limitFD) != -1) {
-        if (limitFD.rlim_cur == RLIM_INFINITY) {
+        if (limitFD.rlim_cur == RLIM_INFINITY ||
+            limitFD.rlim_cur >= static_cast<rlim_t>(std::numeric_limits<int>::max())) {
             // Some platforms implement RLIM_INFINITY as the maximum uint64,
             // others as int64 (-1). Avoid casting even if the return type
-            // is changed to uint64_t.
+            // is changed to uint64_t. We also cap unlikely but possible values
+            // that would overflow int.
             return std::numeric_limits<int>::max();
         }
         if (limitFD.rlim_cur < static_cast<rlim_t>(min_fd)) {

test/functional/feature_init.py

@@ -348,13 +348,23 @@ def init_rlimit_test(self):
         self.log.info("Testing node startup with RLIM_INFINITY fd limit")
         self.restart_node_with_fd_limit(self.RLIM_INFINITY)
 
+    def init_rlimit_large_test(self):
+        """Test that bitcoind starts correctly when the soft RLIMIT_NOFILE limit is above INT_MAX."""
+        if self.RLIM_INFINITY is None:
+            self.log.info("Skipping: resource module not available")
+            return
+
+        self.log.info("Testing node startup with fd limit above INT_MAX")
+        self.restart_node_with_fd_limit(1 << 31)
+
     def run_test(self):
         self.init_pid_test()
         self.init_stress_test_interrupt()
         self.init_stress_test_removals()
         self.break_wait_test()
         self.init_empty_test()
         self.init_rlimit_test()
+        self.init_rlimit_large_test()
 
 
 if __name__ == '__main__':