feat(linear-static-3d-euler-beam): step 9 - dense-math-adapters-review-fix

docs/implementation-plans/linear-static-3d-euler-beam-implementation-report.md

@@ -127,3 +127,20 @@
 - handoff: backend-free `fesa::Vector` and `fesa::Matrix` public APIs, with owning
   dense storage and checked BLAS operations, are available to Step 10 and later
   DOF/element/assembly tasks.
+
+### Review Fix Round 1 — matrix-storage-size-overflow
+
+- regression_test: `tests/unit/math/matrix_test.cpp` now constructs
+  `Matrix{SIZE_MAX / 2 + 1, 2}` and requires `std::length_error`.
+- RED: `cmake --build .harness/build --config Debug --target fesa_tests` exited 0;
+  `ctest --test-dir .harness/build -C Debug -R DenseMath --output-on-failure`
+  exited 8 with 1/2 failures because the wraparound constructor threw nothing.
+- fix: `Matrix` computes its storage size through a checked helper before vector
+  construction and rejects exactly `columns != 0 && rows > SIZE_MAX / columns`.
+- GREEN: the same targeted build and DenseMath CTest commands exited 0; 2/2 passed.
+- VERIFY: approved MSVC x64 configure and full Debug build exited 0; targeted
+  DenseMath passed 2/2, discovery found 7 tests, and the full suite passed 7/7.
+  The public-header MKL scan had zero matches, `git diff --check` exited 0, and
+  `git diff --exit-code -- reference/` exited 0.
+- scope: the deferred empty-dot review minor was not changed, reference artifacts
+  remain untouched, and phase Step 9 status/timestamps were not modified.

src/fesa/math/matrix.cpp

@@ -9,6 +9,15 @@
 namespace fesa {
 namespace {
 
+std::size_t checkedStorageSize(const std::size_t rows, const std::size_t columns) {
+    // Reject shape multiplication overflow before logical dimensions and storage diverge.
+    if (columns != 0 &&
+        rows > (std::numeric_limits<std::size_t>::max)() / columns) {
+        throw std::length_error{"Dense matrix dimensions exceed the storage size range."};
+    }
+    return rows * columns;
+}
+
 MKL_INT toMklSize(const std::size_t size) {
     if (size > static_cast<std::size_t>((std::numeric_limits<MKL_INT>::max)())) {
         throw std::length_error{"Dense matrix dimension exceeds the MKL integer range."};
@@ -30,7 +39,7 @@ Matrix::Matrix(
     const std::size_t rows,
     const std::size_t columns,
     const double value)
-    : rows_(rows), columns_(columns), values_(rows * columns, value) {}
+    : rows_(rows), columns_(columns), values_(checkedStorageSize(rows, columns), value) {}
 
 Matrix::Matrix(const Matrix& other)
     : rows_(other.rows_), columns_(other.columns_), values_(other.values_.size()) {

tests/unit/math/matrix_test.cpp

@@ -2,6 +2,7 @@
 
 #include <gtest/gtest.h>
 
+#include <limits>
 #include <stdexcept>
 #include <utility>
 
@@ -9,6 +10,10 @@ namespace fesa {
 namespace {
 
 TEST(DenseMath, RowMajorMatrixMatchesKnownGemvGemm) {
+    const std::size_t wraparoundRows =
+        (std::numeric_limits<std::size_t>::max)() / 2U + 1U;
+    EXPECT_THROW(static_cast<void>(Matrix{wraparoundRows, 2}), std::length_error);
+
     Matrix zeroRows{0, 3};
     Vector threeValues{3, 2.0};
     const Vector zeroRowProduct = zeroRows.multiply(threeValues);