Read all four submatrices in QuadMatrix::read, not just in Debug

Makefile.am

@@ -113,7 +113,7 @@ unittest_SOURCES=src/test/Range.cpp						\
   src/test/QuadMatrixBuilder.cpp src/test/F4MatrixBuilder.cpp			\
   src/test/F4MatrixReducer.cpp src/test/mathicgb.cpp					\
   src/test/PrimeField.cpp src/test/MonoMonoid.cpp src/test/Scanner.cpp	\
-  src/test/MathicIO.cpp src/test/CFile.cpp
+  src/test/MathicIO.cpp src/test/CFile.cpp src/test/QuadMatrix.cpp
 
 else
 

src/CMakeLists.txt

@@ -80,6 +80,7 @@ if(BUILD_TESTING)
     test/MathicIO.cpp
     test/MonoMonoid.cpp
     test/PrimeField.cpp
+    test/QuadMatrix.cpp
     test/QuadMatrixBuilder.cpp
     test/Range.cpp
     test/Scanner.cpp

src/mathicgb/QuadMatrix.cpp

@@ -356,11 +356,9 @@ SparseMatrix::Scalar QuadMatrix::read(FILE* file) {
   rightColumnMonomials.clear();
 
   const auto topLeftModulus = topLeft.read(file);
-#ifdef MATHICGB_DEBUG
-  const auto topRightModulus = topRight.read(file);
-  const auto bottomLeftModulus = bottomLeft.read(file);
-  const auto bottomRightModulus = bottomRight.read(file);
-#endif
+  [[maybe_unused]] const auto topRightModulus = topRight.read(file);
+  [[maybe_unused]] const auto bottomLeftModulus = bottomLeft.read(file);
+  [[maybe_unused]] const auto bottomRightModulus = bottomRight.read(file);
   // todo: this should throw some kind of invalid format exception instead of
   // these asserts.
   MATHICGB_ASSERT(topLeftModulus == topRightModulus);

src/test/QuadMatrix.cpp

@@ -0,0 +1,44 @@
+// MathicGB copyright 2012 all rights reserved. MathicGB comes with ABSOLUTELY
+// NO WARRANTY and is licensed as GPL v2.0 or later - see LICENSE.txt.
+#include "mathicgb/stdinc.h"
+#include "mathicgb/QuadMatrix.hpp"
+
+#include "mathicgb/CFile.hpp"
+#include <gtest/gtest.h>
+#include <cstdio>
+
+using namespace mgb;
+
+TEST(QuadMatrix, ReadWritesAllFourSubmatrices) {
+  const SparseMatrix::Scalar modulus = 101;
+
+  // A distinct entry per quadrant, so that an empty quadrant and a quadrant
+  // holding another's data both show up.
+  QuadMatrix in;
+  in.topLeft.appendEntry(0, 11);
+  in.topLeft.rowDone();
+  in.topRight.appendEntry(1, 22);
+  in.topRight.rowDone();
+  in.bottomLeft.appendEntry(2, 33);
+  in.bottomLeft.rowDone();
+  in.bottomRight.appendEntry(3, 44);
+  in.bottomRight.rowDone();
+
+  const char* const fileName = "QuadMatrix-test.tmp";
+  {
+    CFile file(fileName, "wb");
+    in.write(modulus, file.handle());
+  }
+
+  QuadMatrix out;
+  {
+    CFile file(fileName, "rb");
+    ASSERT_EQ(modulus, out.read(file.handle()));
+  }
+  ASSERT_EQ(0, std::remove(fileName));
+
+  ASSERT_EQ(in.topLeft.toString(), out.topLeft.toString());
+  ASSERT_EQ(in.topRight.toString(), out.topRight.toString());
+  ASSERT_EQ(in.bottomLeft.toString(), out.bottomLeft.toString());
+  ASSERT_EQ(in.bottomRight.toString(), out.bottomRight.toString());
+}