1 files changed, 136 insertions, 0 deletions

diff --git a/gl/m4/stdckdint_h.m4 b/gl/m4/stdckdint_h.m4
new file mode 100644
index 00000000..d269faa5
--- /dev/null
+++ b/gl/m4/stdckdint_h.m4
@@ -0,0 +1,136 @@
+# stdckdint_h.m4
+# serial 1
+dnl Copyright 2025 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+dnl This file is offered as-is, without any warranty.
+
+dnl Written by Collin Funk.
+
+AC_DEFUN_ONCE([gl_STDCKDINT_H],
+[
+  gl_CHECK_NEXT_HEADERS([stdckdint.h])
+  if test $ac_cv_header_stdckdint_h = yes; then
+    HAVE_STDCKDINT_H=1
+  else
+    HAVE_STDCKDINT_H=0
+  fi
+  AC_SUBST([HAVE_STDCKDINT_H])
+
+  if test $HAVE_STDCKDINT_H = 1; then
+    AC_CACHE_CHECK([whether stdckdint.h can be included in C],
+      [gl_cv_header_c_stdckdint_h],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[#include <stdckdint.h>
+            ]])],
+         [gl_cv_header_c_stdckdint_h=yes],
+         [gl_cv_header_c_stdckdint_h=no])])
+    if test $gl_cv_header_c_stdckdint_h = yes; then
+      HAVE_C_STDCKDINT_H=1
+      AC_CACHE_CHECK([checking for an ISO C23 compliant stdckdint.h in C],
+        [gl_cv_header_c_stdckdint_h_works],
+        [AC_COMPILE_IFELSE(
+           [AC_LANG_PROGRAM(
+              [[#include <stdckdint.h>
+              ]],
+              [[int r;
+                int a = 1;
+                int b = 1;
+                return !!(ckd_add (&r, a, b) || ckd_sub (&r, a, b)
+                          || ckd_mul (&r, a, b));
+              ]])],
+           [gl_cv_header_c_stdckdint_h_works=yes],
+           [gl_cv_header_c_stdckdint_h_works=no])])
+      if test $gl_cv_header_c_stdckdint_h_works = yes; then
+        HAVE_WORKING_C_STDCKDINT_H=1
+      else
+        HAVE_WORKING_C_STDCKDINT_H=0
+      fi
+    else
+      HAVE_C_STDCKDINT_H=0
+      HAVE_WORKING_C_STDCKDINT_H=0
+    fi
+    if test "$CXX" != no; then
+      AC_CACHE_CHECK([whether stdckdint.h can be included in C++],
+        [gl_cv_header_cxx_stdckdint_h],
+        [dnl We can't use AC_LANG_PUSH([C++]) and AC_LANG_POP([C++]) here, due to
+         dnl an autoconf bug <https://savannah.gnu.org/support/?110294>.
+         cat > conftest.cpp <<\EOF
+#include <stdckdint.h>
+EOF
+         gl_command="$CXX $CXXFLAGS $CPPFLAGS -c conftest.cpp"
+         if AC_TRY_EVAL([gl_command]); then
+           gl_cv_header_cxx_stdckdint_h=yes
+         else
+           gl_cv_header_cxx_stdckdint_h=no
+         fi
+         rm -fr conftest*
+        ])
+      if test $gl_cv_header_cxx_stdckdint_h = yes; then
+        HAVE_CXX_STDCKDINT_H=1
+        AC_CACHE_CHECK([checking for an ISO C++26 compliant stdckdint.h in C++],
+          [gl_cv_header_cxx_stdckdint_h_works],
+          [dnl We can't use AC_LANG_PUSH([C++]) and AC_LANG_POP([C++]) here, due to
+           dnl an autoconf bug <https://savannah.gnu.org/support/?110294>.
+           cat > conftest.cpp <<\EOF
+#include <stdckdint.h>
+int
+main (void)
+{
+  int r;
+  int a = 1;
+  int b = 1;
+  return !!(ckd_add (&r, a, b) || ckd_sub (&r, a, b) || ckd_mul (&r, a, b));
+}
+EOF
+           gl_command="$CXX $CXXFLAGS $CPPFLAGS -c conftest.cpp"
+           if AC_TRY_EVAL([gl_command]); then
+             gl_cv_header_cxx_stdckdint_h_works=yes
+           else
+             gl_cv_header_cxx_stdckdint_h_works=no
+           fi
+           rm -fr conftest*
+          ])
+        if test $gl_cv_header_cxx_stdckdint_h_works = yes; then
+          HAVE_WORKING_CXX_STDCKDINT_H=1
+        else
+          HAVE_WORKING_CXX_STDCKDINT_H=0
+        fi
+      else
+        HAVE_CXX_STDCKDINT_H=0
+        HAVE_WORKING_CXX_STDCKDINT_H=0
+      fi
+    fi
+  else
+    HAVE_C_STDCKDINT_H=0
+    HAVE_WORKING_C_STDCKDINT_H=0
+    HAVE_CXX_STDCKDINT_H=0
+    HAVE_WORKING_CXX_STDCKDINT_H=0
+  fi
+  AC_SUBST([HAVE_C_STDCKDINT_H])
+  AC_SUBST([HAVE_WORKING_C_STDCKDINT_H])
+  AC_SUBST([HAVE_CXX_STDCKDINT_H])
+  AC_SUBST([HAVE_WORKING_CXX_STDCKDINT_H])
+
+  if test "$CXX" != no; then
+    dnl We might need the header for C or C++.
+    if test $HAVE_C_STDCKDINT_H = 1 \
+       && test $HAVE_WORKING_C_STDCKDINT_H = 1 \
+       && test $HAVE_CXX_STDCKDINT_H = 1 \
+       && test $HAVE_WORKING_CXX_STDCKDINT_H = 1; then
+      GL_GENERATE_STDCKDINT_H=false
+    else
+      GL_GENERATE_STDCKDINT_H=true
+    fi
+  else
+    dnl We don't care about C++ here.
+    if test $HAVE_C_STDCKDINT_H = 1 \
+       && test $HAVE_WORKING_C_STDCKDINT_H = 1; then
+      GL_GENERATE_STDCKDINT_H=false
+    else
+      GL_GENERATE_STDCKDINT_H=true
+    fi
+  fi
+])