From bd0ad31f7750c784b8b287fd4376d836e190dc8a Mon Sep 17 00:00:00 2001
From: Robin Getz <rgetz503@gmail.com>
Date: Sat, 25 Jul 2026 15:28:57 -0400
Subject: [PATCH 1/2] demoddatv: Fix spectrum compilation against current
 cfft_engine API

The spectrum template was not being instantiated by the current build,
so stale accesses to cfft_engine::n went unnoticed.

Replace direct accesses to the private cfft_engine member with the
public size() accessor. This restores spectrum compilation and allows
the upcoming VLA cleanup to be built and tested.

Signed-off-by: Robin Getz <rgetz503@gmail.com>
---
 plugins/channelrx/demoddatv/leansdr/sdr.h | 24 ++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/plugins/channelrx/demoddatv/leansdr/sdr.h b/plugins/channelrx/demoddatv/leansdr/sdr.h
index 9ce9cdf5b..f5acd900f 100644
--- a/plugins/channelrx/demoddatv/leansdr/sdr.h
+++ b/plugins/channelrx/demoddatv/leansdr/sdr.h
@@ -2086,9 +2086,10 @@ struct spectrum : runnable
 
     void run()
     {
-        while (in.readable() >= fft.n * decim && out.writable() >= 1)
+        const int fft_size = fft.size();
+        while (in.readable() >= fft_size * decim && out.writable() >= 1)
         {
-            phase += fft.n * decim;
+            phase += fft_size * decim;
 
             if (phase >= decimation)
             {
@@ -2096,24 +2097,25 @@ struct spectrum : runnable
                 do_spectrum();
             }
 
-            in.read(fft.n * decim);
+            in.read(fft_size * decim);
         }
     }
 
   private:
     void do_spectrum()
     {
-        std::complex<T> data[fft.n];
+        const int fft_size = fft.size();
+        std::complex<T> data[fft_size];
 
         if (decim == 1)
         {
-            memcpy(data, in.rd(), fft.n * sizeof(data[0]));
+            memcpy(data, in.rd(), fft_size * sizeof(data[0]));
         }
         else
         {
             std::complex<T> *pin = in.rd();
 
-            for (int i = 0; i < fft.n; ++i, pin += decim) {
+            for (int i = 0; i < fft_size; ++i, pin += decim) {
                 data[i] = *pin;
             }
         }
@@ -2121,23 +2123,23 @@ struct spectrum : runnable
         fft.inplace(data, true);
         float power[NFFT];
 
-        for (int i = 0; i < fft.n; ++i) {
+        for (int i = 0; i < fft_size; ++i) {
             power[i] = (float)data[i].real() * data[i].real() + (float)data[i].imag() * data[i].imag();
         }
 
         if (!avgpower)
         {
             // Initialize with first spectrum
-            avgpower = new float[fft.n];
-            memcpy(avgpower, power, fft.n * sizeof(avgpower[0]));
+            avgpower = new float[fft_size];
+            memcpy(avgpower, power, fft_size * sizeof(avgpower[0]));
         }
 
         // Accumulate and low-pass filter
-        for (int i = 0; i < fft.n; ++i)
+        for (int i = 0; i < fft_size; ++i)
             avgpower[i] = avgpower[i] * (1 - kavg) + power[i] * kavg;
 
         // Reuse power[]
-        for (int i = 0; i < fft.n / 2; ++i)
+        for (int i = 0; i < fft_size / 2; ++i)
         {
             power[i] = 10 * log10f(avgpower[NFFT / 2 + i]);
             power[NFFT / 2 + i] = 10 * log10f(avgpower[i]);

From fef5c27425b55e95427e322720b80f1201e453e4 Mon Sep 17 00:00:00 2001
From: Robin Getz <rgetz503@gmail.com>
Date: Sat, 25 Jul 2026 15:44:41 -0400
Subject: [PATCH 2/2] demoddatv: Replace spectrum VLA with std::vector

Replace the runtime-sized stack array in the spectrum processing path
with std::vector to avoid compiler VLA extensions.

Although the spectrum template is not instantiated as part of the
current SDRangel build, GCC still emits -Wvla warnings while parsing
the template definition. This change removes those warnings and keeps
the template valid for future use.

Use std::copy() and vector::data() when accessing the underlying
storage.

Part of #2830

Signed-off-by: Robin Getz <rgetz503@gmail.com>
---
 plugins/channelrx/demoddatv/leansdr/sdr.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/plugins/channelrx/demoddatv/leansdr/sdr.h b/plugins/channelrx/demoddatv/leansdr/sdr.h
index f5acd900f..42f555ee3 100644
--- a/plugins/channelrx/demoddatv/leansdr/sdr.h
+++ b/plugins/channelrx/demoddatv/leansdr/sdr.h
@@ -19,8 +19,10 @@
 #ifndef LEANSDR_SDR_H
 #define LEANSDR_SDR_H
 
-#include <numeric>
+#include <algorithm>
 #include <complex>
+#include <numeric>
+#include <vector>
 
 #include "leansdr/dsp.h"
 #include "leansdr/math.h"
@@ -2105,11 +2107,11 @@ struct spectrum : runnable
     void do_spectrum()
     {
         const int fft_size = fft.size();
-        std::complex<T> data[fft_size];
+        std::vector<std::complex<T>> data(fft_size);
 
         if (decim == 1)
         {
-            memcpy(data, in.rd(), fft_size * sizeof(data[0]));
+            std::copy(in.rd(), in.rd() + fft_size, data.begin());
         }
         else
         {
@@ -2120,7 +2122,7 @@ struct spectrum : runnable
             }
         }
 
-        fft.inplace(data, true);
+        fft.inplace(data.data(), true);
         float power[NFFT];
 
         for (int i = 0; i < fft_size; ++i) {