From 067d9e9ce97dd42b8b13eef10031b0fa9cf23a1f Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 9 Sep 2017 09:16:59 +0000
Subject: [PATCH] sprintf.c: NULL as str

* sprintf.c (ruby_vsnprintf, ruby_snprintf): allow NULL as str,
  just count the expected buffer size.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59789 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ext/-test-/printf/printf.c |  8 ++++++++
 sprintf.c                  | 20 ++++++++++++++------
 test/-ext-/test_printf.rb  |  4 ++++
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/ext/-test-/printf/printf.c b/ext/-test-/printf/printf.c
index 666f5592e5..e793bb7a48 100644
--- a/ext/-test-/printf/printf.c
+++ b/ext/-test-/printf/printf.c
@@ -90,6 +90,13 @@ printf_test_call(int argc, VALUE *argv, VALUE self)
     return rb_assoc_new(result, rb_usascii_str_new_cstr(format));
 }
 
+static VALUE
+snprintf_count(VALUE self, VALUE str)
+{
+    int n = ruby_snprintf(NULL, 0, "%s", StringValueCStr(str));
+    return INT2FIX(n);
+}
+
 void
 Init_printf(void)
 {
@@ -98,4 +105,5 @@ Init_printf(void)
     rb_define_singleton_method(m, "v", printf_test_v, 1);
     rb_define_singleton_method(m, "q", printf_test_q, 1);
     rb_define_singleton_method(m, "call", printf_test_call, -1);
+    rb_define_singleton_method(m, "sncount", snprintf_count, 1);
 }
diff --git a/sprintf.c b/sprintf.c
index 4ee7e1d4f0..2bd4966a1b 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -1261,21 +1261,29 @@ ruby_ultoa(unsigned long val, char *endp, int base, int flags)
     return BSD__ultoa(val, endp, base, octzero, xdigs);
 }
 
+static int ruby_do_vsnprintf(char *str, size_t n, const char *fmt, va_list ap);
+
 int
 ruby_vsnprintf(char *str, size_t n, const char *fmt, va_list ap)
+{
+    if (str && (ssize_t)n < 1)
+	return (EOF);
+    return ruby_do_vsnprintf(str, n, fmt, ap);
+}
+
+static int
+ruby_do_vsnprintf(char *str, size_t n, const char *fmt, va_list ap)
 {
     int ret;
     rb_printf_buffer f;
 
-    if ((int)n < 1)
-	return (EOF);
     f._flags = __SWR | __SSTR;
     f._bf._base = f._p = (unsigned char *)str;
-    f._bf._size = f._w = n - 1;
+    f._bf._size = f._w = str ? (n - 1) : 0;
     f.vwrite = BSD__sfvwrite;
     f.vextra = 0;
     ret = (int)BSD_vfprintf(&f, fmt, ap);
-    *f._p = 0;
+    if (str) *f._p = 0;
     return ret;
 }
 
@@ -1285,11 +1293,11 @@ ruby_snprintf(char *str, size_t n, char const *fmt, ...)
     int ret;
     va_list ap;
 
-    if ((int)n < 1)
+    if (str && (ssize_t)n < 1)
 	return (EOF);
 
     va_start(ap, fmt);
-    ret = ruby_vsnprintf(str, n, fmt, ap);
+    ret = ruby_do_vsnprintf(str, n, fmt, ap);
     va_end(ap);
     return ret;
 }
diff --git a/test/-ext-/test_printf.rb b/test/-ext-/test_printf.rb
index 4e4f5b4695..cd3ba76364 100644
--- a/test/-ext-/test_printf.rb
+++ b/test/-ext-/test_printf.rb
@@ -184,4 +184,8 @@ class Test_SPrintf < Test::Unit::TestCase
     assert_equal("  a", Bug::Printf.("s", "a", width: 3, prec: 3)[0])
     assert_equal("a  ", Bug::Printf.("s", "a", minus: true, width: 3, prec: 3)[0])
   end
+
+  def test_snprintf_count
+    assert_equal(3, Bug::Printf.sncount("foo"))
+  end
 end