From e09e02527e403268516226e6a72385747fe02ad2 Mon Sep 17 00:00:00 2001
From: Susi Lehtola <susi.lehtola@gmail.com>
Date: Fri, 6 Feb 2026 10:15:43 +0200
Subject: [PATCH 1/3] Add sanity check for number of primitives

---
 include/gauxc/shell.hpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/gauxc/shell.hpp b/include/gauxc/shell.hpp
index 7f27170c3..d47864785 100644
--- a/include/gauxc/shell.hpp
+++ b/include/gauxc/shell.hpp
@@ -138,6 +138,9 @@ class alignas(256) Shell {
     alpha_( alpha ), coeff_( coeff ), O_( O ),
     nprim_( nprim.get() ), l_( l.get() ), pure_( pure.get() ) {
 
+    if(nprim_ > detail::shell_nprim_max)
+      throw std::out_of_range("Shell has too many primitives!\n");
+
     if( _normalize ) normalize();
     compute_shell_cutoff();
 

From 4c28c8b06f0b928cd992de5d78611975a592bfb0 Mon Sep 17 00:00:00 2001
From: Susi Lehtola <susi.lehtola@gmail.com>
Date: Fri, 6 Feb 2026 17:55:22 +0200
Subject: [PATCH 2/3] Revision based on code review: include expected and
 erroneous values.

---
 include/gauxc/shell.hpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/gauxc/shell.hpp b/include/gauxc/shell.hpp
index d47864785..01d35f429 100644
--- a/include/gauxc/shell.hpp
+++ b/include/gauxc/shell.hpp
@@ -138,8 +138,11 @@ class alignas(256) Shell {
     alpha_( alpha ), coeff_( coeff ), O_( O ),
     nprim_( nprim.get() ), l_( l.get() ), pure_( pure.get() ) {
 
-    if(nprim_ > detail::shell_nprim_max)
-      throw std::out_of_range("Shell has too many primitives!\n");
+    if(nprim_ > detail::shell_nprim_max) {
+      std::ostringstream oss;
+      oss << "Shell has too many primitives! expected <= " << detail::shell_nprim_max << " actual value " << nprim_ << "!\n";
+      throw std::out_of_range(oss.str());
+    }
 
     if( _normalize ) normalize();
     compute_shell_cutoff();

From c28504d87a6999c7c85c596516103a85ebefc262 Mon Sep 17 00:00:00 2001
From: Sebastian Ehlert <sehlert@microsoft.com>
Date: Mon, 27 Apr 2026 08:58:48 +0200
Subject: [PATCH 3/3] Add test case and fix imports

---
 include/gauxc/shell.hpp |  4 +++-
 tests/basisset_test.cxx | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/include/gauxc/shell.hpp b/include/gauxc/shell.hpp
index 01d35f429..32cb50e65 100644
--- a/include/gauxc/shell.hpp
+++ b/include/gauxc/shell.hpp
@@ -14,6 +14,8 @@
 #include <array>
 #include <cmath>
 #include <iostream>
+#include <sstream>
+#include <stdexcept>
 #include <cassert>
 #include <algorithm>
 #include <tuple>
@@ -138,7 +140,7 @@ class alignas(256) Shell {
     alpha_( alpha ), coeff_( coeff ), O_( O ),
     nprim_( nprim.get() ), l_( l.get() ), pure_( pure.get() ) {
 
-    if(nprim_ > detail::shell_nprim_max) {
+    if(nprim_ > static_cast<int32_t>(detail::shell_nprim_max)) {
       std::ostringstream oss;
       oss << "Shell has too many primitives! expected <= " << detail::shell_nprim_max << " actual value " << nprim_ << "!\n";
       throw std::out_of_range(oss.str());
diff --git a/tests/basisset_test.cxx b/tests/basisset_test.cxx
index 295653369..51fa39556 100644
--- a/tests/basisset_test.cxx
+++ b/tests/basisset_test.cxx
@@ -20,6 +20,8 @@
 
 #include <random>
 #include <algorithm>
+#include <stdexcept>
+#include <string>
 
 #include <gauxc/gauxc_config.hpp>
 
@@ -184,6 +186,25 @@ TEST_CASE("Shell", "[basisset]") {
 
   }
 
+  SECTION("Too Many Primitives") {
+
+    const auto nprim = PrimSize(detail::shell_nprim_max + 1);
+    const prim_array alpha = {0.8};
+    const prim_array coeff = {0.5};
+
+    try {
+      Shell<double> sh( nprim, AngularMomentum(0), SphericalType(false),
+        alpha, coeff, center );
+      FAIL( "Expected Shell construction to throw" );
+    } catch( const std::out_of_range& ex ) {
+      const std::string message = ex.what();
+      CHECK( message.find( "Shell has too many primitives!" ) != std::string::npos );
+      CHECK( message.find( "expected <= 32" ) != std::string::npos );
+      CHECK( message.find( "actual value 33" ) != std::string::npos );
+    }
+
+  }
+
 }