Fix removed tgamma error handling path

include/boost/math/special_functions/gamma.hpp

@@ -197,25 +197,30 @@
 {
    BOOST_MATH_STD_USING
 
-   if(z <= -20)
-   {
-      constexpr auto function = "boost::math::tgamma<%1%>(%1%)";
-      T result = gamma_imp_final(T(-z), pol, l) * sinpx(z);
-      BOOST_MATH_INSTRUMENT_VARIABLE(result);
-      if((fabs(result) < 1) && (tools::max_value<T>() * fabs(result) < boost::math::constants::pi<T>()))
-         return -boost::math::sign(result) * policies::raise_overflow_error<T>(function, "Result of tgamma is too large to represent.", pol);
-      result = -boost::math::constants::pi<T>() / result;
-      if(result == 0)
-         return policies::raise_underflow_error<T>(function, "Result of tgamma is too small to represent.", pol);
-      if((boost::math::fpclassify)(result) == (int)BOOST_MATH_FP_SUBNORMAL)
-         return policies::raise_denorm_error<T>(function, "Result of tgamma is denormalized.", result, pol);
-      BOOST_MATH_INSTRUMENT_VARIABLE(result);
-      return result;
-   }
-   else
+   T result = 1;
+   constexpr auto function = "boost::math::tgamma<%1%>(%1%)";
+
+   if(z <= 0)
    {
-      return gamma_imp_final(T(z), pol, l);
+      if(floor(z) == z)
+         return policies::raise_pole_error<T>(function, "Evaluation of tgamma at a negative integer %1%.", z, pol);
+      if(z <= -20)
+      {
+         result = gamma_imp_final(T(-z), pol, l) * sinpx(z);
+         BOOST_MATH_INSTRUMENT_VARIABLE(result);
+         if((fabs(result) < 1) && (tools::max_value<T>() * fabs(result) < boost::math::constants::pi<T>()))
+            return -boost::math::sign(result) * policies::raise_overflow_error<T>(function, "Result of tgamma is too large to represent.", pol);
+         result = -boost::math::constants::pi<T>() / result;
+         if(result == 0)
+            return policies::raise_underflow_error<T>(function, "Result of tgamma is too small to represent.", pol);
+         if((boost::math::fpclassify)(result) == BOOST_MATH_FP_SUBNORMAL)
+            return policies::raise_denorm_error<T>(function, "Result of tgamma is denormalized.", result, pol);
+         BOOST_MATH_INSTRUMENT_VARIABLE(result);
+         return result;
+      }
    }
+
+   return gamma_imp_final(T(z), pol, l);
 }
 
 #ifdef BOOST_MATH_ENABLE_CUDA

test/Jamfile.v2

@@ -193,6 +193,7 @@ test-suite special_fun :
    [ run git_issue_1137.cpp ]
    [ run git_issue_1139.cpp ]
    [ run git_issue_1175.cpp ]
+   [ run git_issue_1194.cpp ]
    [ run special_functions_test.cpp /boost/test//boost_unit_test_framework  ]
    [ run test_airy.cpp test_instances//test_instances pch_light /boost/test//boost_unit_test_framework  ]
    [ run test_bessel_j.cpp test_instances//test_instances pch_light /boost/test//boost_unit_test_framework  ]

test/git_issue_1194.cpp

@@ -0,0 +1,41 @@
+//  (C) Copyright Matt Borland 2024.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include "math_unit_test.hpp"
+#include <boost/math/special_functions/gamma.hpp>
+#include <cerrno>
+
+int main()
+{
+    using c99_error_policy = ::boost::math::policies::policy<
+            ::boost::math::policies::domain_error< ::boost::math::policies::errno_on_error>,
+            ::boost::math::policies::pole_error< ::boost::math::policies::errno_on_error>,
+            ::boost::math::policies::overflow_error< ::boost::math::policies::errno_on_error>,
+            ::boost::math::policies::evaluation_error< ::boost::math::policies::errno_on_error>,
+            ::boost::math::policies::rounding_error< ::boost::math::policies::errno_on_error> >;
+
+    double val = -std::numeric_limits<double>::infinity();
+
+    val = boost::math::tgamma(val, c99_error_policy());
+    CHECK_EQUAL(errno, EDOM);
+
+    val = std::numeric_limits<double>::quiet_NaN();
+    val = boost::math::tgamma(val, c99_error_policy());
+    CHECK_EQUAL(errno, EDOM);
+
+    val = std::numeric_limits<double>::infinity();
+    val = boost::math::tgamma(val, c99_error_policy());
+    CHECK_EQUAL(errno, ERANGE);
+
+    val = 0;
+    val = boost::math::tgamma(val, c99_error_policy());
+    CHECK_EQUAL(errno, EDOM); // OK
+
+    val = -2;
+    val = boost::math::tgamma(val, c99_error_policy());
+    CHECK_EQUAL(errno, EDOM); // OK
+
+    return boost::math::test::report_errors();
+}