Add bureaucracy for openacc in autotools

etc/m4/atrip_openacc.m4

@@ -0,0 +1,70 @@
+#   SYNOPSIS
+#
+#   ATRIP_OPENACC([ACTION-SUCCESS], [ACTION-FAILURE])
+#
+#   DESCRIPTION
+#
+#   Check whether the given the -fopenacc flag works with the current language's compiler
+#   or gives an error.
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   LICENSE
+#
+#   Copyright (c) 2023 Alejandro Gallo <aamsgallo@gmail.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+AC_DEFUN([ATRIP_OPENACC],
+[
+AC_MSG_CHECKING([that the compiler works with the -fopenacc])
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([_ATRIP_OPENACC_SOURCE])],
+                  [
+                   $1
+                   AC_MSG_RESULT([yes])
+                   ],
+                  [
+                   $2
+                   AC_MSG_ERROR([no])
+                   ])
+])dnl DEFUN
+
+m4_define([_ATRIP_OPENACC_SOURCE], [[
+#include <stdio.h>
+#include <stdlib.h>
+#include <openacc.h>
+
+#define SIZE 10
+
+int main(int argc, char **argv) {
+  float matrix[SIZE * SIZE];
+  float result[SIZE * SIZE];
+
+  // Initialize the matrix with random values
+  for (int i = 0; i < SIZE * SIZE; i++) {
+    matrix[i] = rand() / (float)RAND_MAX;
+  }
+
+#pragma acc data                                            \
+        copy(matrix[0:SIZE * SIZE])           \
+        copyout(result[0:SIZE * SIZE])
+  {
+    // Calculate the matrix multiplication
+#pragma acc parallel loop collapse(2)
+    for (int i = 0; i < SIZE; i++) {
+      for (int j = 0; j < SIZE; j++) {
+        float sum = 0.0f;
+        for (int k = 0; k < SIZE; k++) {
+          sum += matrix[i * SIZE + k] * matrix[j * SIZE + k];
+        }
+        result[i * SIZE + j] = sum;
+      }
+    }
+  }
+  return 0;
+}
+]])

etc/m4/ax_cxx_compile_stdcxx.m4

@@ -43,7 +43,7 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 14
+#serial 15
 
 dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
 dnl  (serial version number 13).
@@ -189,7 +189,11 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 201103L
+// MSVC always sets __cplusplus to 199711L in older versions; newer versions
+// only set it correctly if /Zc:__cplusplus is specified as well as a
+// /std:c++NN switch:
+// https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
+#elif __cplusplus < 201103L && !defined _MSC_VER
 
 #error "This is not a C++11 compiler"
 
@@ -480,7 +484,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 201402L
+#elif __cplusplus < 201402L && !defined _MSC_VER
 
 #error "This is not a C++14 compiler"
 
@@ -604,7 +608,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 201703L
+#elif __cplusplus < 201703L && !defined _MSC_VER
 
 #error "This is not a C++17 compiler"
 
@@ -970,7 +974,7 @@ namespace cxx17
 
 }  // namespace cxx17
 
-#endif  // __cplusplus < 201703L
+#endif  // __cplusplus < 201703L && !defined _MSC_VER
 
 ]])
 
@@ -983,7 +987,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_20], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 202002L
+#elif __cplusplus < 202002L && !defined _MSC_VER
 
 #error "This is not a C++20 compiler"
 
@@ -1000,6 +1004,6 @@ namespace cxx20
 
 }  // namespace cxx20
 
-#endif  // __cplusplus < 202002L
+#endif  // __cplusplus < 202002L && !defined _MSC_VER
 
 ]])