Fix zero-padding bug with (format "%#08x" n)

Problem reported by Gustaf Waldemarson (Bug#29609).
* src/editfns.c (styled_format):
Put zero padding after a leading "0x", not before.
* test/src/editfns-tests.el (format-sharp-0-x): New test.

diff --git a/src/editfns.c b/src/editfns.c
index e671ba0761cc28c2698795b741da73d3da310e52..ebf6518994b93880bc13727e8db4c58e9c496ed8 100644 (file)
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -4722,11 +4722,19 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
                  char src0 = src[0];
                  int exponent_bytes = 0;
                  bool signedp = src0 == '-' || src0 == '+' || src0 == ' ';
-                 unsigned char after_sign = src[signedp];
-                 if (zero_flag && 0 <= char_hexdigit (after_sign))
+                 int prefix_bytes = (signedp
+                                     + ((src[signedp] == '0'
+                                         && (src[signedp + 1] == 'x'
+                                             || src[signedp + 1] == 'X'))
+                                        ? 2 : 0));
+                 if (zero_flag)
                    {
-                     leading_zeros += padding;
-                     padding = 0;
+                     unsigned char after_prefix = src[prefix_bytes];
+                     if (0 <= char_hexdigit (after_prefix))
+                       {
+                         leading_zeros += padding;
+                         padding = 0;
+                       }
                    }
 
                  if (excess_precision
@@ -4745,13 +4753,13 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
                      nchars += padding;
                    }
 
-                 *p = src0;
-                 src += signedp;
-                 p += signedp;
+                 memcpy (p, src, prefix_bytes);
+                 p += prefix_bytes;
+                 src += prefix_bytes;
                  memset (p, '0', leading_zeros);
                  p += leading_zeros;
                  int significand_bytes
-                   = sprintf_bytes - signedp - exponent_bytes;
+                   = sprintf_bytes - prefix_bytes - exponent_bytes;
                  memcpy (p, src, significand_bytes);
                   p += significand_bytes;
                  src += significand_bytes;

diff --git a/test/src/editfns-tests.el b/test/src/editfns-tests.el
index 70dc9372fad18380287e8a518cc5a9039030f014..283a642dd97877412fad0958c929d41e7bbd47f3 100644 (file)
--- a/test/src/editfns-tests.el
+++ b/test/src/editfns-tests.el
@@ -136,6 +136,12 @@
 (ert-deftest format-c-float ()
   (should-error (format "%c" 0.5)))
 
+;;; Test for Bug#29609.
+(ert-deftest format-sharp-0-x ()
+  (should (string-equal (format "%#08x" #x10) "0x000010"))
+  (should (string-equal (format "%#05X" #x10) "0X010"))
+  (should (string-equal (format "%#04x" 0) "0000")))
+
 ;;; Check format-time-string with various TZ settings.
 ;;; Use only POSIX-compatible TZ values, since the tests should work
 ;;; even if tzdb is not in use.