Don't check how to copy a va_list if we already have va_copy()

If we already have ISO C va_copy() or its non-standard counterpart
__va_copy(), then there's no need to do an AC_RUN_IFELSE or its
CMake equivalent to detect whether "args2 = args1" or "*args2 = *args1"
works. AC_RUN_IFELSE is problematic during cross-compilation, where the
program cannot be run (you have to know in advance that the test program
will be run and what its result will be), so we want to avoid it whenever
possible.

Signed-off-by: Simon McVittie <smcv@collabora.com>

2 files changed, 53 insertions, 55 deletions

diff --git a/cmake/ConfigureChecks.cmake b/cmake/ConfigureChecks.cmake
index 310b1bbb..04180322 100644
--- a/cmake/ConfigureChecks.cmake
+++ b/cmake/ConfigureChecks.cmake
@@ -120,26 +120,26 @@ elseif(HAVE___VA_COPY)
 else()
     # this is used for msvc < 2013
     set(DBUS_VA_COPY _DBUS_VA_COPY_ASSIGN)
-endif()
 
-CHECK_C_SOURCE_RUNS("
-#include <stdarg.h>
-#include <stdlib.h>
-static void f (int i, ...) {
-    va_list args1, args2;
-    va_start (args1, i);
-    args2 = args1;
-    if (va_arg (args2, int) != 42 || va_arg (args1, int) != 42)
-    exit (1);
-    va_end (args1); va_end (args2);
-}
-int main() {
-    f (0, 42);
-    return 0;
-}
-" VA_COPY_AS_ARRAY)
-if (NOT VA_COPY_AS_ARRAY)
-    set(DBUS_VA_COPY_AS_ARRAY 1 CACHE STRING "Set to 1 if va_list cannot be copied as a value")
+    CHECK_C_SOURCE_RUNS("
+    #include <stdarg.h>
+    #include <stdlib.h>
+    static void f (int i, ...) {
+        va_list args1, args2;
+        va_start (args1, i);
+        args2 = args1;
+        if (va_arg (args2, int) != 42 || va_arg (args1, int) != 42)
+            exit (1);
+        va_end (args1); va_end (args2);
+    }
+    int main() {
+        f (0, 42);
+        return 0;
+    }
+    " VA_COPY_AS_ARRAY)
+    if (NOT VA_COPY_AS_ARRAY)
+        set(DBUS_VA_COPY_AS_ARRAY 1 CACHE STRING "Set to 1 if va_list cannot be copied as a value")
+    endif()
 endif()
 
 CHECK_C_SOURCE_COMPILES("
diff --git a/configure.ac b/configure.ac
index 89337836..fa542290 100644
--- a/configure.ac
+++ b/configure.ac
@@ -563,42 +563,40 @@ else if test "x$dbus_cv___va_copy" = "xyes"; then
 fi
 fi
 
-if test -n "$dbus_va_copy_func"; then
-  AC_DEFINE_UNQUOTED(DBUS_VA_COPY,$dbus_va_copy_func,[A 'va_copy' style function])
-fi
-
-AC_LANG_PUSH(C)
-AC_CACHE_CHECK([whether va_lists can be copied by value],
-	dbus_cv_va_val_copy,
-	[AC_RUN_IFELSE([AC_LANG_PROGRAM(
-[[
-	#include <stdarg.h>
-	#include <stdlib.h>
-]],
-[[
-	static void f (int i, ...) {
-	va_list args1, args2;
-	va_start (args1, i);
-	args2 = args1;
-	if (va_arg (args2, int) != 42 || va_arg (args1, int) != 42)
-	  exit (1);
-	va_end (args1); va_end (args2);
-	}
-	int main() {
-	  f (0, 42);
-	  return 0;
-	}
-]])],
-	[dbus_cv_va_val_copy=yes],
-	[dbus_cv_va_val_copy=no],
-	[dbus_cv_va_val_copy=yes])
-])
-AC_LANG_POP(C)
-
-if test "x$dbus_cv_va_val_copy" = "xno"; then
-  AC_DEFINE(DBUS_VA_COPY_AS_ARRAY,1, ['va_lists' cannot be copies as values])
-fi
-
+AS_IF([test -n "$dbus_va_copy_func"],
+  [AC_DEFINE_UNQUOTED([DBUS_VA_COPY], [$dbus_va_copy_func], [A 'va_copy' style function])],
+  [
+    AC_LANG_PUSH([C])
+    AC_CACHE_CHECK([whether va_lists can be copied by value],
+                   [dbus_cv_va_val_copy],
+                   [AC_RUN_IFELSE([
+                      AC_LANG_PROGRAM([[
+                        #include <stdarg.h>
+                        #include <stdlib.h>
+                      ]],
+                      [[
+                        static void f (int i, ...) {
+                          va_list args1, args2;
+                          va_start (args1, i);
+                          args2 = args1;
+                          if (va_arg (args2, int) != 42 || va_arg (args1, int) != 42)
+                            exit (1);
+                          va_end (args1); va_end (args2);
+                        }
+                        int main() {
+                          f (0, 42);
+                          return 0;
+                        }
+                      ]])
+                    ],
+                    [dbus_cv_va_val_copy=yes],
+                    [dbus_cv_va_val_copy=no],
+                    [dbus_cv_va_val_copy=yes])
+                   ])
+    AC_LANG_POP([C])
+    AS_IF([test "x$dbus_cv_va_val_copy" = "xno"],
+      [AC_DEFINE([DBUS_VA_COPY_AS_ARRAY], 1, [Define if 'va_list' cannot be copied as a value])])
+  ])
 
 #### Atomic integers