cross-compilation guesses (4)

[Bruno Haible]

When cross-compiling, configure says:

  checking for working getgroups... no

Here's a proposed patch for improving this in gnulib. Again, would it be
better to modify AC_FUNC_GETGROUPS in Autoconf?


2012-05-01  Bruno Haible  <address@hidden>

        getgroups: Avoid "guessing no" when cross-compiling to glibc systems.
        * m4/getgroups.m4 (gl_FUNC_GETGROUPS): When cross-compiling, set
        ac_cv_func_getgroups_works without invoking AC_FUNC_GETGROUPS.

--- m4/getgroups.m4.orig        Tue May  1 23:17:52 2012
+++ m4/getgroups.m4     Tue May  1 23:17:30 2012
@@ -1,4 +1,4 @@
-# serial 17
+# serial 18
 
 dnl From Jim Meyering.
 dnl A wrapper around AC_FUNC_GETGROUPS.
@@ -11,40 +11,64 @@
 
 AC_DEFUN([gl_FUNC_GETGROUPS],
 [
-  AC_REQUIRE([AC_FUNC_GETGROUPS])
   AC_REQUIRE([AC_TYPE_GETGROUPS])
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+
+  AC_CHECK_FUNCS([getgroups])
   if test "$ac_cv_func_getgroups" != yes; then
     HAVE_GETGROUPS=0
-  elif test "$ac_cv_func_getgroups_works.$ac_cv_type_getgroups" != yes.gid_t
-  then
-    REPLACE_GETGROUPS=1
-    AC_DEFINE([GETGROUPS_ZERO_BUG], [1], [Define this to 1 if
-      getgroups(0,NULL) does not return the number of groups.])
   else
-    dnl Detect FreeBSD bug; POSIX requires getgroups(-1,ptr) to fail.
-    AC_CACHE_CHECK([whether getgroups handles negative values],
-      [gl_cv_func_getgroups_works],
-      [AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
-        [[int size = getgroups (0, 0);
-          gid_t *list = malloc (size * sizeof *list);
-          return getgroups (-1, list) != -1;]])],
-        [gl_cv_func_getgroups_works=yes],
-        [gl_cv_func_getgroups_works=no],
-        [case "$host_os" in
-                   # Guess yes on glibc systems.
-           *-gnu*) gl_cv_func_getgroups_works="guessing yes" ;;
-                   # If we don't know, assume the worst.
-           *)      gl_cv_func_getgroups_works="guessing no" ;;
-         esac
-        ])])
-    case "$gl_cv_func_getgroups_works" in
-      *yes) ;;
-      *)
-        REPLACE_GETGROUPS=1
+    if test $cross_compiling = no; then
+      AC_FUNC_GETGROUPS
+    else
+      dnl Improved cross-compilation guess.
+      case "$host_os" in
+                # Guess yes on glibc systems.
+        *-gnu*) ac_cv_func_getgroups_works="guessing yes" ;;
+                # If we don't know, assume the worst.
+        *)      ac_cv_func_getgroups_works="guessing no" ;;
+      esac
+    fi
+    case "$ac_cv_func_getgroups" in
+      *yes)
+        AC_DEFINE([HAVE_GETGROUPS], [1],
+          [Define to 1 if your system has a working 'getgroups' function.])
         ;;
     esac
+    if test "$ac_cv_type_getgroups" != gid_t \
+       || { case "$ac_cv_func_getgroups_works in
+              *yes) false;;
+              *) true;;
+            esac
+          }; then
+      REPLACE_GETGROUPS=1
+      AC_DEFINE([GETGROUPS_ZERO_BUG], [1], [Define this to 1 if
+        getgroups(0,NULL) does not return the number of groups.])
+    else
+      dnl Detect FreeBSD bug; POSIX requires getgroups(-1,ptr) to fail.
+      AC_CACHE_CHECK([whether getgroups handles negative values],
+        [gl_cv_func_getgroups_works],
+        [AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
+          [[int size = getgroups (0, 0);
+            gid_t *list = malloc (size * sizeof *list);
+            return getgroups (-1, list) != -1;]])],
+          [gl_cv_func_getgroups_works=yes],
+          [gl_cv_func_getgroups_works=no],
+          [case "$host_os" in
+                     # Guess yes on glibc systems.
+             *-gnu*) gl_cv_func_getgroups_works="guessing yes" ;;
+                     # If we don't know, assume the worst.
+             *)      gl_cv_func_getgroups_works="guessing no" ;;
+           esac
+          ])])
+      case "$gl_cv_func_getgroups_works" in
+        *yes) ;;
+        *)
+          REPLACE_GETGROUPS=1
+          ;;
+      esac
+    fi
   fi
   test -n "$GETGROUPS_LIB" && LIBS="$GETGROUPS_LIB $LIBS"
 ])