Testing for `good' support of probed v?snprintf

Thanks to Jarkko, and Russ

p4raw-id: //depot/metaconfig@26667

diff --git a/U/perl/d_snprintf.U b/U/perl/d_snprintf.U
index a8cc875..26e80f6 100644 (file)
--- a/U/perl/d_snprintf.U
+++ b/U/perl/d_snprintf.U
@@ -6,7 +6,7 @@
 ?RCS: that same Artistic Licence; a copy of which may be found at the root
 ?RCS: of the source tree for dist 3.0.
 ?RCS:
-?MAKE:d_snprintf d_vsnprintf : Inlibc
+?MAKE:d_snprintf d_vsnprintf : Inlibc Compile cat run rm
 ?MAKE: -pick add $@ %<
 ?S:d_snprintf:
 ?S:    This variable conditionally defines the HAS_SNPRINTF symbol, which
@@ -38,3 +38,60 @@ eval $inlibc
 set vsnprintf d_vsnprintf
 eval $inlibc
 
+case "$d_snprintf-$d_vsnprintf" in
+"$define-$define")
+    $cat <<EOM
+Checking whether your snprintf() and vsnprintf() work okay...
+EOM
+    $cat >try.c <<'EOCP'
+/* v?snprintf testing logic courtesy of Russ Allbery.
+ * According to C99:
+ * - if the buffer is too short it still must be \0-terminated
+ * - if the buffer is too short the potentially required length
+ *   must be returned and not -1
+ * - if the buffer is NULL the potentially required length
+ *   must be returned and not -1 or core dump
+ */
+#include <stdio.h>
+#include <stdarg.h>
+
+char buf[2];
+
+int test (char *format, ...)
+{
+    va_list args;
+    int count;
+
+    va_start (args, format);
+    count = vsnprintf (buf, sizeof buf, format, args);
+    va_end (args);
+    return count;
+}
+
+int main ()
+{
+    return ((test ("%s", "abcd") == 4 && buf[0] == 'a' && buf[1] == '\0'
+             && snprintf (NULL, 0, "%s", "abcd") == 4) ? 0 : 1);
+}
+EOCP
+    set try
+    if eval $compile; then
+       `$run ./try`
+       case "$?" in
+       0) echo "Your snprintf() and vsnprintf() seem to be working okay." ;;
+       *) cat <<EOM >&4
+Your snprintf() and snprintf() don't seem to be working okay.
+EOM
+          d_snprintf="$undef"
+          d_vsnprintf="$undef"
+          ;;
+       esac
+    else
+       echo "(I can't seem to compile the test program--assuming they don't)"
+       d_snprintf="$undef"
+       d_vsnprintf="$undef"
+    fi
+    $rm -f try.* try core core.try.*
+    ;;
+esac
+