host: Add static_assert to prevent meta_range_t(0,0)

meta_range_t(0,0) actually calls the iterator-based constructor for
meta_range_t, which is almost certainly not the intended constructor
for that call syntax. Therefore, we add a static_assert to prevent
such usage, and fix all failing instances.

host/include/uhd/types/ranges.hpp

@@ -9,6 +9,7 @@
 
 #include <uhd/config.hpp>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 namespace uhd {
@@ -76,6 +77,14 @@ struct UHD_API meta_range_t : std::vector<range_t>
     meta_range_t(InputIterator first, InputIterator last)
         : std::vector<range_t>(first, last)
     { /* NOP */
+        // This is to avoid people accidentally doing silly things like:
+        // meta_range_t(0, 0)
+        // which probably was supposed to call meta_range_t(double, double, double)
+        // but actually calls this constructor.
+        static_assert(
+            !std::is_integral<typename std::decay<InputIterator>::type>::value,
+            "You can't pass integers to meta_range_t's constructor!"
+        );
     }
 
     /*!

host/lib/rfnoc/radio_control_impl.cpp

@@ -767,7 +767,7 @@ void radio_control_impl::set_tx_dc_offset(const std::complex<double>&, size_t)
 
 uhd::meta_range_t radio_control_impl::get_tx_dc_offset_range(size_t) const
 {
-    return uhd::meta_range_t(0, 0);
+    return uhd::meta_range_t(0.0, 0.0);
 }
 
 void radio_control_impl::set_tx_iq_balance(const std::complex<double>&, size_t)
@@ -792,7 +792,7 @@ void radio_control_impl::set_rx_dc_offset(const std::complex<double>&, size_t)
 
 uhd::meta_range_t radio_control_impl::get_rx_dc_offset_range(size_t) const
 {
-    return uhd::meta_range_t(0, 0);
+    return uhd::meta_range_t(0.0, 0.0);
 }
 
 void radio_control_impl::set_rx_iq_balance(const bool enb, size_t)

host/lib/usrp/multi_usrp.cpp

@@ -1847,7 +1847,7 @@ public:
         } else {
             UHD_LOGGER_WARNING("MULTI_USRP")
                 << "This device does not support querying the RX DC offset range.";
-            return meta_range_t(0, 0);
+            return meta_range_t(0.0, 0.0);
         }
     }
 
@@ -2340,7 +2340,7 @@ public:
         } else {
             UHD_LOGGER_WARNING("MULTI_USRP")
                 << "This device does not support querying the TX DC offset range.";
-            return meta_range_t(0, 0);
+            return meta_range_t(0.0, 0.0);
         }
     }
 

host/lib/usrp/multi_usrp_rfnoc.cpp

@@ -1209,7 +1209,7 @@ public:
             rx_chain.radio->get_rx_frequency_range(rx_chain.block_chan);
         freq_range_t dsp_range =
             (rx_chain.ddc) ? rx_chain.ddc->get_frequency_range(rx_chain.block_chan)
-                           : meta_range_t(0, 0);
+                           : meta_range_t(0.0, 0.0);
         // Create lambdas to feed to tune_xx_subdev_and_dsp()
         // Note: If there is no DDC present, register empty lambdas for the DSP functions
         auto set_rf_freq = [rx_chain](double freq) {
@@ -1840,7 +1840,7 @@ public:
             tx_chain.radio->get_tx_frequency_range(tx_chain.block_chan);
         freq_range_t dsp_range =
             (tx_chain.duc) ? tx_chain.duc->get_frequency_range(tx_chain.block_chan)
-                           : meta_range_t(0, 0);
+                           : meta_range_t(0.0, 0.0);
         // Create lambdas to feed to tune_xx_subdev_and_dsp()
         // Note: If there is no DDC present, register empty lambdas for the DSP functions
         auto set_rf_freq = [tx_chain](double freq) {

host/lib/usrp/x300/x300_radio_control.cpp

@@ -821,7 +821,7 @@ public:
         } else {
             RFNOC_LOG_WARNING(
                 "This device does not support querying the TX DC offset range.");
-            return meta_range_t(0, 0);
+            return meta_range_t(0.0, 0.0);
         }
     }
 
@@ -864,7 +864,7 @@ public:
         } else {
             RFNOC_LOG_WARNING(
                 "This device does not support querying the rx DC offset range.");
-            return meta_range_t(0, 0);
+            return meta_range_t(0.0, 0.0);
         }
     }
 

mpm/lib/mykonos/ad937x_ctrl.cpp

@@ -129,7 +129,7 @@ uhd::meta_range_t ad937x_ctrl::get_rf_freq_range(void)
 uhd::meta_range_t ad937x_ctrl::get_bw_filter_range(void)
 {
     // TODO: fix
-    return uhd::meta_range_t(0, 1);
+    return uhd::meta_range_t(0.0, 1.0);
 }
 
 std::vector<double> ad937x_ctrl::get_clock_rates(void)