diff -Naurd mpfr-4.0.1-a/PATCHES mpfr-4.0.1-b/PATCHES
--- mpfr-4.0.1-a/PATCHES	2018-07-31 11:26:25.226690969 +0000
+++ mpfr-4.0.1-b/PATCHES	2018-07-31 11:26:25.262690428 +0000
@@ -0,0 +1 @@
+vasprintf-p-length-modifier
diff -Naurd mpfr-4.0.1-a/VERSION mpfr-4.0.1-b/VERSION
--- mpfr-4.0.1-a/VERSION	2018-07-31 11:21:08.887430085 +0000
+++ mpfr-4.0.1-b/VERSION	2018-07-31 11:26:25.262690428 +0000
@@ -1 +1 @@
-4.0.1-p12
+4.0.1-p13
diff -Naurd mpfr-4.0.1-a/src/mpfr.h mpfr-4.0.1-b/src/mpfr.h
--- mpfr-4.0.1-a/src/mpfr.h	2018-07-31 11:21:08.887430085 +0000
+++ mpfr-4.0.1-b/src/mpfr.h	2018-07-31 11:26:25.262690428 +0000
@@ -27,7 +27,7 @@
 #define MPFR_VERSION_MAJOR 4
 #define MPFR_VERSION_MINOR 0
 #define MPFR_VERSION_PATCHLEVEL 1
-#define MPFR_VERSION_STRING "4.0.1-p12"
+#define MPFR_VERSION_STRING "4.0.1-p13"
 
 /* User macros:
    MPFR_USE_FILE:        Define it to make MPFR define functions dealing
diff -Naurd mpfr-4.0.1-a/src/vasprintf.c mpfr-4.0.1-b/src/vasprintf.c
--- mpfr-4.0.1-a/src/vasprintf.c	2018-07-31 11:21:08.771431816 +0000
+++ mpfr-4.0.1-b/src/vasprintf.c	2018-07-31 11:26:25.246690670 +0000
@@ -259,6 +259,8 @@
     }
 }
 
+/* Note: additional flags should be added to the MPFR_PREC_ARG code
+   for gmp_asprintf (when supported). */
 static const char *
 parse_flags (const char *format, struct printf_spec *specinfo)
 {
@@ -2220,7 +2222,7 @@
         /* output mpfr_prec_t variable */
         {
           char *s;
-          char format[MPFR_PREC_FORMAT_SIZE + 6]; /* see examples below */
+          char format[MPFR_PREC_FORMAT_SIZE + 12]; /* e.g. "%0#+ -'*.*ld\0" */
           size_t length;
           mpfr_prec_t prec;
 
@@ -2232,14 +2234,14 @@
           start = fmt;
 
           /* construct format string, like "%*.*hd" "%*.*d" or "%*.*ld" */
-          format[0] = '%';
-          format[1] = '*';
-          format[2] = '.';
-          format[3] = '*';
-          format[4] = '\0';
-          strcat (format, MPFR_PREC_FORMAT_TYPE);
-          format[4 + MPFR_PREC_FORMAT_SIZE] = spec.spec;
-          format[5 + MPFR_PREC_FORMAT_SIZE] = '\0';
+          sprintf (format, "%%%s%s%s%s%s%s*.*" MPFR_PREC_FORMAT_TYPE "%c",
+                   spec.pad == '0' ? "0" : "",
+                   spec.alt ? "#" : "",
+                   spec.showsign ? "+" : "",
+                   spec.space ? " " : "",
+                   spec.left ? "-" : "",
+                   spec.group ? "'" : "",
+                   spec.spec);
           length = gmp_asprintf (&s, format, spec.width, spec.prec, prec);
           MPFR_ASSERTN (length >= 0);  /* guaranteed by GMP 6 */
           buffer_cat (&buf, s, length);
diff -Naurd mpfr-4.0.1-a/src/version.c mpfr-4.0.1-b/src/version.c
--- mpfr-4.0.1-a/src/version.c	2018-07-31 11:21:08.887430085 +0000
+++ mpfr-4.0.1-b/src/version.c	2018-07-31 11:26:25.262690428 +0000
@@ -25,5 +25,5 @@
 const char *
 mpfr_get_version (void)
 {
-  return "4.0.1-p12";
+  return "4.0.1-p13";
 }
diff -Naurd mpfr-4.0.1-a/tests/tsprintf.c mpfr-4.0.1-b/tests/tsprintf.c
--- mpfr-4.0.1-a/tests/tsprintf.c	2018-07-10 15:46:13.648796978 +0000
+++ mpfr-4.0.1-b/tests/tsprintf.c	2018-07-31 11:26:25.250690608 +0000
@@ -232,6 +232,22 @@
   /* specifier 'P' for precision */
   check_vsprintf ("128", "%Pu", p);
   check_vsprintf ("00128", "%.5Pu", p);
+  check_vsprintf ("  128", "%5Pu", p);
+  check_vsprintf ("000128", "%06Pu", p);
+  check_vsprintf ("128    :", "%-7Pu:", p);
+  check_vsprintf ("000128:", "%-2.6Pd:", p);
+  check_vsprintf ("  000128:", "%8.6Pd:", p);
+  check_vsprintf ("000128  :", "%-8.6Pd:", p);
+  check_vsprintf ("+128:", "%+d:", p);
+  check_vsprintf (" 128:", "% d:", p);
+  check_vsprintf ("80:", "% x:", p);
+  check_vsprintf ("0x80:", "% #x:", p);
+  check_vsprintf ("0x80:", "%0#+ -x:", p);
+  check_vsprintf ("0200:", "%0#+ -o:", p);
+  check_vsprintf ("+0000128 :", "%0+ *.*Pd:", -9, 7, p);
+  check_vsprintf ("+12345   :", "%0+ -*.*Pd:", -9, -3, (mpfr_prec_t) 12345);
+  /* Do not add a test like "%05.1Pd" as MS Windows is buggy: when
+     a precision is given, the '0' flag must be ignored. */
 
   /* special numbers */
   mpfr_set_inf (x, 1);